diff --git a/mypy.ini b/mypy.ini
index 947693e4..2fb7f4b3 100644
--- a/mypy.ini
+++ b/mypy.ini
@@ -8,7 +8,7 @@ ignore_missing_imports = True
 [mypy-build123d.topology.jupyter_tools.*]
 ignore_missing_imports = True
 
-[mypy-IPython.lib.pretty.*]
+[mypy-IPython.*]
 ignore_missing_imports = True
 
 [mypy-numpy.*]
@@ -28,3 +28,12 @@ ignore_missing_imports = True
 
 [mypy-vtkmodules.*]
 ignore_missing_imports = True
+
+[mypy-ezdxf.*]
+ignore_missing_imports = True
+
+[mypy-setuptools_scm.*]
+ignore_missing_imports = True
+
+[mypy-py_lib3mf.*]
+ignore_missing_imports = True
diff --git a/src/build123d/build_common.py b/src/build123d/build_common.py
index f5fef9b7..92a785ea 100644
--- a/src/build123d/build_common.py
+++ b/src/build123d/build_common.py
@@ -243,7 +243,7 @@ def __init__(
         self.builder_parent = None
         self.lasts: dict = {Vertex: [], Edge: [], Face: [], Solid: []}
         self.workplanes_context = None
-        self.exit_workplanes = None
+        self.exit_workplanes: list[Plane] = []
         self.obj_before: Shape | None = None
         self.to_combine: list[Shape] = []
 
diff --git a/src/build123d/drafting.py b/src/build123d/drafting.py
index e2929e10..2c995abe 100644
--- a/src/build123d/drafting.py
+++ b/src/build123d/drafting.py
@@ -29,7 +29,7 @@
 from dataclasses import dataclass
 from datetime import date
 from math import copysign, floor, gcd, log2, pi
-from typing import ClassVar, Optional, Union
+from typing import cast, ClassVar, TypeAlias
 
 from collections.abc import Iterable
 
@@ -102,7 +102,7 @@ class Arrow(BaseSketchObject):
 
     Args:
         arrow_size (float): arrow head tip to tail length
-        shaft_path (Union[Edge, Wire]): line describing the shaft shape
+        shaft_path (Edge |  Wire): line describing the shaft shape
         shaft_width (float): line width of shaft
         head_at_start (bool, optional): Defaults to True.
         head_type (HeadType, optional): arrow head shape. Defaults to HeadType.CURVED.
@@ -141,17 +141,15 @@ def __init__(
         shaft_pen = shaft_path.perpendicular_line(shaft_width, 0)
         shaft = sweep(shaft_pen, shaft_path, mode=Mode.PRIVATE)
 
-        arrow = arrow_head.fuse(shaft).clean()
+        arrow = cast(Compound, arrow_head.fuse(shaft)).clean()
 
         super().__init__(arrow, rotation=0, align=None, mode=mode)
 
 
-PathDescriptor = Union[
-    Wire,
-    Edge,
-    list[Union[Vector, Vertex, tuple[float, float, float]]],
-]
-PointLike = Union[Vector, Vertex, tuple[float, float, float]]
+PointLike: TypeAlias = Vector | Vertex | tuple[float, float, float]
+"""General type for points in 3D space"""
+PathDescriptor: TypeAlias = Wire | Edge | list[PointLike]
+"""General type for a path in 3D space"""
 
 
 @dataclass
@@ -223,7 +221,7 @@ def _round_to_str(self, number: float) -> str:
     def _number_with_units(
         self,
         number: float,
-        tolerance: float | tuple[float, float] = None,
+        tolerance: float | tuple[float, float] | None = None,
         display_units: bool | None = None,
     ) -> str:
         """Convert a raw number to a unit of measurement string based on the class settings"""
@@ -295,7 +293,7 @@ def _process_path(path: PathDescriptor) -> Edge | Wire:
 
     def _label_to_str(
         self,
-        label: str,
+        label: str | None,
         line_wire: Wire,
         label_angle: bool,
         tolerance: float | tuple[float, float] | None,
@@ -351,7 +349,7 @@ class DimensionLine(BaseSketchObject):
             argument is desired not an actual measurement. Defaults to None.
         arrows (tuple[bool, bool], optional): a pair of boolean values controlling the placement
             of the start and end arrows. Defaults to (True, True).
-        tolerance (Union[float, tuple[float, float]], optional): an optional tolerance
+        tolerance (float | tuple[float, float], optional): an optional tolerance
             value to add to the extracted length value. If a single tolerance value is provided
             it is shown as ± the provided value while a pair of values are shown as
             separate + and - values. Defaults to None.
@@ -368,14 +366,14 @@ class DimensionLine(BaseSketchObject):
     def __init__(
         self,
         path: PathDescriptor,
-        draft: Draft = None,
-        sketch: Sketch = None,
-        label: str = None,
+        draft: Draft,
+        sketch: Sketch | None = None,
+        label: str | None = None,
         arrows: tuple[bool, bool] = (True, True),
-        tolerance: float | tuple[float, float] = None,
+        tolerance: float | tuple[float, float] | None = None,
         label_angle: bool = False,
         mode: Mode = Mode.ADD,
-    ) -> Sketch:
+    ):
         # pylint: disable=too-many-locals
 
         context = BuildSketch._get_context(self)
@@ -452,22 +450,35 @@ def __init__(
             flip_label = path_obj.tangent_at(u_value).get_angle(Vector(1, 0, 0)) >= 180
             loc = Draft._sketch_location(path_obj, u_value, flip_label)
             placed_label = label_shape.located(loc)
-            self_intersection = Sketch.intersect(d_line, placed_label).area
+            self_intersection = cast(
+                Sketch | None, Sketch.intersect(d_line, placed_label)
+            )
+            if self_intersection is None:
+                self_intersection_area = 0.0
+            else:
+                self_intersection_area = self_intersection.area
             d_line += placed_label
             bbox_size = d_line.bounding_box().size
 
             # Minimize size while avoiding intersections
-            common_area = (
-                0.0 if sketch is None else Sketch.intersect(d_line, sketch).area
-            )
-            common_area += self_intersection
+            if sketch is None:
+                common_area = 0.0
+            else:
+                line_intersection = cast(
+                    Sketch | None, Sketch.intersect(d_line, sketch)
+                )
+                if line_intersection is None:
+                    common_area = 0.0
+                else:
+                    common_area = line_intersection.area
+            common_area += self_intersection_area
             score = (d_line.area - 10 * common_area) / bbox_size.X
             d_lines[d_line] = score
 
         # Sort by score to find the best option
-        d_lines = sorted(d_lines.items(), key=lambda x: x[1])
+        sorted_d_lines = sorted(d_lines.items(), key=lambda x: x[1])
 
-        super().__init__(obj=d_lines[-1][0], rotation=0, align=None, mode=mode)
+        super().__init__(obj=sorted_d_lines[-1][0], rotation=0, align=None, mode=mode)
 
 
 class ExtensionLine(BaseSketchObject):
@@ -489,7 +500,7 @@ class ExtensionLine(BaseSketchObject):
             is desired not an actual measurement. Defaults to None.
         arrows (tuple[bool, bool], optional): a pair of boolean values controlling the placement
             of the start and end arrows. Defaults to (True, True).
-        tolerance (Union[float, tuple[float, float]], optional): an optional tolerance
+        tolerance (float | tuple[float, float], optional): an optional tolerance
             value to add to the extracted length value. If a single tolerance value is provided
             it is shown as ± the provided value while a pair of values are shown as
             separate + and - values. Defaults to None.
@@ -507,12 +518,12 @@ def __init__(
         border: PathDescriptor,
         offset: float,
         draft: Draft,
-        sketch: Sketch = None,
-        label: str = None,
+        sketch: Sketch | None = None,
+        label: str | None = None,
         arrows: tuple[bool, bool] = (True, True),
-        tolerance: float | tuple[float, float] = None,
+        tolerance: float | tuple[float, float] | None = None,
         label_angle: bool = False,
-        project_line: VectorLike = None,
+        project_line: VectorLike | None = None,
         mode: Mode = Mode.ADD,
     ):
         # pylint: disable=too-many-locals
@@ -531,7 +542,7 @@ def __init__(
         if offset == 0:
             raise ValueError("A dimension line should be used if offset is 0")
         dimension_path = object_to_measure.offset_2d(
-            distance=offset, side=side_lut[copysign(1, offset)], closed=False
+            distance=offset, side=side_lut[int(copysign(1, offset))], closed=False
         )
         dimension_label_str = (
             label
@@ -629,7 +640,7 @@ def __init__(
         title: str = "Title",
         sub_title: str = "Sub Title",
         drawing_number: str = "B3D-1",
-        sheet_number: int = None,
+        sheet_number: int | None = None,
         drawing_scale: float = 1.0,
         nominal_text_size: float = 10.0,
         line_width: float = 0.5,
@@ -691,12 +702,12 @@ def __init__(
             4: 3 / 12,
             5: 5 / 12,
         }
-        for i, label in enumerate(["F", "E", "D", "C", "B", "A"]):
+        for i, grid_label in enumerate(["F", "E", "D", "C", "B", "A"]):
             for y_index in [-0.5, 0.5]:
                 grid_labels += Pos(
                     x_centers[i] * frame_width,
                     y_index * (frame_height + 1.5 * nominal_text_size),
-                ) * Sketch(Compound.make_text(label, nominal_text_size).wrapped)
+                ) * Sketch(Compound.make_text(grid_label, nominal_text_size).wrapped)
 
         # Text Box Frame
         bf_pnt1 = frame_wire.edges().sort_by(Axis.Y)[0] @ 0.5
diff --git a/src/build123d/exporters.py b/src/build123d/exporters.py
index 9d0ba2e2..810d9c91 100644
--- a/src/build123d/exporters.py
+++ b/src/build123d/exporters.py
@@ -34,9 +34,9 @@
 import xml.etree.ElementTree as ET
 from copy import copy
 from enum import Enum, auto
-from os import PathLike, fsdecode, fspath
-from pathlib import Path
-from typing import List, Optional, Tuple, Union
+from os import PathLike, fsdecode
+from typing import Any, TypeAlias
+from warnings import warn
 
 from collections.abc import Callable, Iterable
 
@@ -45,16 +45,15 @@
 from ezdxf import zoom
 from ezdxf.colors import RGB, aci2rgb
 from ezdxf.math import Vec2
-from OCP.BRepLib import BRepLib  # type: ignore
-from OCP.BRepTools import BRepTools_WireExplorer  # type: ignore
-from OCP.Geom import Geom_BezierCurve  # type: ignore
-from OCP.GeomConvert import GeomConvert  # type: ignore
-from OCP.GeomConvert import GeomConvert_BSplineCurveToBezierCurve  # type: ignore
-from OCP.gp import gp_Ax2, gp_Dir, gp_Pnt, gp_Vec, gp_XYZ  # type: ignore
-from OCP.HLRAlgo import HLRAlgo_Projector  # type: ignore
-from OCP.HLRBRep import HLRBRep_Algo, HLRBRep_HLRToShape  # type: ignore
-from OCP.TopAbs import TopAbs_Orientation, TopAbs_ShapeEnum  # type: ignore
-from OCP.TopExp import TopExp_Explorer  # type: ignore
+from OCP.BRepLib import BRepLib
+from OCP.Geom import Geom_BezierCurve
+from OCP.GeomConvert import GeomConvert
+from OCP.GeomConvert import GeomConvert_BSplineCurveToBezierCurve
+from OCP.gp import gp_Ax2, gp_Dir, gp_Pnt, gp_Vec, gp_XYZ
+from OCP.HLRAlgo import HLRAlgo_Projector
+from OCP.HLRBRep import HLRBRep_Algo, HLRBRep_HLRToShape
+from OCP.TopAbs import TopAbs_Orientation, TopAbs_ShapeEnum
+from OCP.TopExp import TopExp_Explorer
 from OCP.TopoDS import TopoDS
 from typing_extensions import Self
 
@@ -69,7 +68,8 @@
 )
 from build123d.build_common import UNITS_PER_METER
 
-PathSegment = Union[PT.Line, PT.Arc, PT.QuadraticBezier, PT.CubicBezier]
+PathSegment: TypeAlias = PT.Line | PT.Arc | PT.QuadraticBezier | PT.CubicBezier
+"""A type alias for the various path segment types in the svgpathtools library."""
 
 # ---------------------------------------------------------------------------
 # ---------------------------------------------------------------------------
@@ -82,7 +82,7 @@ def __init__(
         self,
         shape: Shape,
         *,
-        look_at: VectorLike = None,
+        look_at: VectorLike | None = None,
         look_from: VectorLike = (1, -1, 1),
         look_up: VectorLike = (0, 0, 1),
         with_hidden: bool = True,
@@ -562,7 +562,7 @@ def add_layer(
         """
         # ezdxf :doc:`line type <ezdxf-stable:concepts/linetypes>`.
 
-        kwargs = {}
+        kwargs: dict[str, Any] = {}
 
         if line_type is not None:
             linetype = self._linetype(line_type)
@@ -587,7 +587,7 @@ def _linetype(self, line_type: LineType) -> str:
             # The linetype is not in the doc yet.
             # Add it from our available definitions.
             if linetype in Export2D.LINETYPE_DEFS:
-                desc, pattern = Export2D.LINETYPE_DEFS.get(linetype)
+                desc, pattern = Export2D.LINETYPE_DEFS.get(linetype)  # type: ignore[misc]
                 self._document.linetypes.add(
                     name=linetype,
                     pattern=[self._linetype_scale * v for v in pattern],
@@ -605,7 +605,7 @@ def add_shape(self, shape: Shape | Iterable[Shape], layer: str = "") -> Self:
         Adds a shape to the specified layer.
 
         Args:
-            shape (Union[Shape, Iterable[Shape]]): The shape or collection of shapes to be
+            shape (Shape | Iterable[Shape]): The shape or collection of shapes to be
                   added. It can be a single Shape object or an iterable of Shape objects.
             layer (str, optional): The name of the layer where the shape will be
                 added. If not specified, the default layer will be used. Defaults to "".
@@ -641,8 +641,8 @@ def write(self, file_name: PathLike | str | bytes):
         Writes the DXF data to the specified file name.
 
         Args:
-            file_name (Union[PathLike, str, bytes]): The file name (including path) where the DXF data will
-                be written.
+            file_name (PathLike |  str |  bytes): The file name (including path) where
+                the DXF data will be written.
         """
         # Reset the main CAD viewport of the model space to the
         # extents of its entities.
@@ -757,6 +757,8 @@ def _convert_bspline(self, edge: Edge, attribs):
         )
 
         # need to apply the transform on the geometry level
+        if edge.wrapped is None or edge.location is None:
+            raise ValueError(f"Edge is empty {edge}.")
         t = edge.location.wrapped.Transformation()
         spline.Transform(t)
 
@@ -828,17 +830,17 @@ class ExportSVG(Export2D):
             should fit the strokes of the shapes. Defaults to True.
         precision (int, optional): The number of decimal places used for rounding
             coordinates in the SVG. Defaults to 6.
-        fill_color (Union[ColorIndex, RGB, None], optional): The default fill color
+        fill_color (ColorIndex |  RGB |  None, optional): The default fill color
             for shapes. It can be specified as a ColorIndex, an RGB tuple, or None.
             Defaults to None.
-        line_color (Union[ColorIndex, RGB, None], optional): The default line color for
+        line_color (ColorIndex |  RGB |  None, optional): The default line color for
             shapes. It can be specified as a ColorIndex or an RGB tuple, or None.
             Defaults to Export2D.DEFAULT_COLOR_INDEX.
         line_weight (float, optional): The default line weight (stroke width) for
             shapes, in millimeters. Defaults to Export2D.DEFAULT_LINE_WEIGHT.
         line_type (LineType, optional): The default line type for shapes. It should be
             a LineType enum. Defaults to Export2D.DEFAULT_LINE_TYPE.
-        dot_length (Union[DotLength, float], optional): The width of rendered dots in a
+        dot_length (DotLength |  float, optional): The width of rendered dots in a
             Can be either a DotLength enum or a float value in tenths of an inch.
             Defaults to DotLength.INKSCAPE_COMPAT.
 
@@ -878,21 +880,28 @@ def __init__(
             line_type: LineType,
         ):
             def convert_color(
-                c: ColorIndex | RGB | Color | None,
+                input_color: ColorIndex | RGB | Color | None,
             ) -> Color | None:
-                if isinstance(c, ColorIndex):
+                if isinstance(input_color, ColorIndex):
                     # The easydxf color indices BLACK and WHITE have the same
                     # value (7), and are both mapped to (255,255,255) by the
                     # aci2rgb() function.  We prefer (0,0,0).
-                    if c == ColorIndex.BLACK:
-                        c = RGB(0, 0, 0)
+                    if input_color == ColorIndex.BLACK:
+                        rgb_color = RGB(0, 0, 0)
                     else:
-                        c = aci2rgb(c.value)
-                elif isinstance(c, tuple):
-                    c = RGB(*c)
-                if isinstance(c, RGB):
-                    c = Color(*c.to_floats(), 1)
-                return c
+                        rgb_color = aci2rgb(input_color.value)
+                elif isinstance(input_color, tuple):
+                    rgb_color = RGB(*input_color)
+                else:
+                    rgb_color = input_color  # If not ColorIndex or tuple, it's already RGB or None
+
+                if isinstance(rgb_color, RGB):
+                    red, green, blue = rgb_color.to_floats()
+                    final_color = Color(red, green, blue, 1.0)
+                else:
+                    final_color = rgb_color  # If not RGB, it's None or already a Color
+
+                return final_color
 
             self.name = name
             self.fill_color = convert_color(fill_color)
@@ -929,7 +938,7 @@ def __init__(
         self.dot_length = dot_length
         self._non_planar_point_count = 0
         self._layers: dict[str, ExportSVG._Layer] = {}
-        self._bounds: BoundBox = None
+        self._bounds: BoundBox | None = None
 
         # Add the default layer.
         self.add_layer(
@@ -957,10 +966,10 @@ def add_layer(
 
         Args:
             name (str): The name of the layer. Must be unique among all layers.
-            fill_color (Union[ColorIndex, RGB, Color, None], optional): The fill color for shapes
+            fill_color (ColorIndex |  RGB |  Color |  None, optional): The fill color for shapes
                 on this layer. It can be specified as a ColorIndex, an RGB tuple,
                 a Color, or None.  Defaults to None.
-            line_color (Union[ColorIndex, RGB, Color, None], optional): The line color for shapes on
+            line_color (ColorIndex |  RGB |  Color |  None, optional): The line color for shapes on
                 this layer. It can be specified as a ColorIndex or an RGB tuple,
                 a Color, or None.  Defaults to Export2D.DEFAULT_COLOR_INDEX.
             line_weight (float, optional): The line weight (stroke width) for shapes on
@@ -1002,7 +1011,7 @@ def add_shape(
         Adds a shape or a collection of shapes to the specified layer.
 
         Args:
-            shape (Union[Shape, Iterable[Shape]]): The shape or collection of shapes to be
+            shape (Shape | Iterable[Shape]): The shape or collection of shapes to be
                   added. It can be a single Shape object or an iterable of Shape objects.
             layer (str, optional): The name of the layer where the shape(s) will be added.
                 Defaults to "".
@@ -1014,12 +1023,12 @@ def add_shape(
         """
         if layer not in self._layers:
             raise ValueError(f"Undefined layer: {layer}.")
-        layer = self._layers[layer]
+        _layer = self._layers[layer]
         if isinstance(shape, Shape):
-            self._add_single_shape(shape, layer, reverse_wires)
+            self._add_single_shape(shape, _layer, reverse_wires)
         else:
             for s in shape:
-                self._add_single_shape(s, layer, reverse_wires)
+                self._add_single_shape(s, _layer, reverse_wires)
 
     def _add_single_shape(self, shape: Shape, layer: _Layer, reverse_wires: bool):
         # pylint: disable=too-many-locals
@@ -1188,6 +1197,12 @@ def _line_element(self, edge: Edge) -> ET.Element:
 
     def _circle_segments(self, edge: Edge, reverse: bool) -> list[PathSegment]:
         # pylint: disable=too-many-locals
+        if edge.length < 1e-6:
+            warn(
+                "Skipping arc that is too small to export safely (length < 1e-6).",
+                stacklevel=7,
+            )
+            return []
         curve = edge.geom_adaptor()
         circle = curve.Circle()
         radius = circle.Radius()
@@ -1234,6 +1249,12 @@ def _circle_element(self, edge: Edge) -> ET.Element:
 
     def _ellipse_segments(self, edge: Edge, reverse: bool) -> list[PathSegment]:
         # pylint: disable=too-many-locals
+        if edge.length < 1e-6:
+            warn(
+                "Skipping ellipse that is too small to export safely (length < 1e-6).",
+                stacklevel=7,
+            )
+            return []
         curve = edge.geom_adaptor()
         ellipse = curve.Ellipse()
         minor_radius = ellipse.MinorRadius()
@@ -1283,6 +1304,8 @@ def _bspline_segments(self, edge: Edge, reverse: bool) -> list[PathSegment]:
         u2 = adaptor.LastParameter()
 
         # Apply the shape location to the geometry.
+        if edge.wrapped is None or edge.location is None:
+            raise ValueError(f"Edge is empty {edge}.")
         t = edge.location.wrapped.Transformation()
         spline.Transform(t)
         # describe_bspline(spline)
@@ -1347,6 +1370,8 @@ def _other_element(self, edge: Edge) -> ET.Element:
     }
 
     def _edge_segments(self, edge: Edge, reverse: bool) -> list[PathSegment]:
+        if edge.wrapped is None:
+            raise ValueError(f"Edge is empty {edge}.")
         edge_reversed = edge.wrapped.Orientation() == TopAbs_Orientation.TopAbs_REVERSED
         geom_type = edge.geom_type
         segments = self._SEGMENT_LOOKUP.get(geom_type, ExportSVG._other_segments)
@@ -1391,10 +1416,12 @@ def _stroke_dasharray(self, layer: _Layer):
 
     # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
-    def _group_for_layer(self, layer: _Layer, attribs: dict = None) -> ET.Element:
-        def _color_attribs(c: Color) -> tuple[str, str]:
-            if c:
-                (r, g, b, a) = tuple(c)
+    def _group_for_layer(
+        self, layer: _Layer, attribs: dict | None = None
+    ) -> ET.Element:
+        def _color_attribs(color: Color | None) -> tuple[str, str | None]:
+            if color is not None:
+                (r, g, b, a) = tuple(color)
                 (r, g, b, a) = (int(r * 255), int(g * 255), int(b * 255), round(a, 3))
                 rgb = f"rgb({r},{g},{b})"
                 opacity = f"{a}" if a < 1 else None
@@ -1403,9 +1430,9 @@ def _color_attribs(c: Color) -> tuple[str, str]:
 
         if attribs is None:
             attribs = {}
-        (fill, fill_opacity) = _color_attribs(layer.fill_color)
+        fill, fill_opacity = _color_attribs(layer.fill_color)
         attribs["fill"] = fill
-        if fill_opacity:
+        if fill_opacity is not None:
             attribs["fill-opacity"] = fill_opacity
         (stroke, stroke_opacity) = _color_attribs(layer.line_color)
         attribs["stroke"] = stroke
@@ -1435,10 +1462,12 @@ def write(self, path: PathLike | str | bytes):
         Writes the SVG data to the specified file path.
 
         Args:
-            path (Union[PathLike, str, bytes]): The file path where the SVG data will be written.
+            path (PathLike |  str |  bytes): The file path where the SVG data will be written.
         """
         # pylint: disable=too-many-locals
         bb = self._bounds
+        if bb is None:
+            raise ValueError("No shapes to export.")
         doc_margin = self.margin
         if self.fit_to_stroke:
             max_line_weight = max(l.line_weight for l in self._layers.values())
@@ -1479,4 +1508,5 @@ def write(self, path: PathLike | str | bytes):
 
         xml = ET.ElementTree(svg)
         ET.indent(xml, "  ")
-        xml.write(path, encoding="utf-8", xml_declaration=True, default_namespace=False)
+        # xml.write(path, encoding="utf-8", xml_declaration=True, default_namespace=False)
+        xml.write(path, encoding="utf-8", xml_declaration=True, default_namespace=None)
diff --git a/src/build123d/objects_part.py b/src/build123d/objects_part.py
index cce0175f..9a3da0e9 100644
--- a/src/build123d/objects_part.py
+++ b/src/build123d/objects_part.py
@@ -30,12 +30,11 @@
 
 from math import radians, tan
 
-from typing import Union
 from build123d.build_common import LocationList, validate_inputs
 from build123d.build_enums import Align, Mode
 from build123d.build_part import BuildPart
-from build123d.geometry import Location, Plane, Rotation, RotationLike, Vector
-from build123d.topology import Compound, Part, Solid, tuplify
+from build123d.geometry import Location, Plane, Rotation, RotationLike
+from build123d.topology import Compound, Part, ShapeList, Solid, tuplify
 
 
 class BasePartObject(Part):
@@ -46,7 +45,7 @@ class BasePartObject(Part):
     Args:
         solid (Solid): object to create
         rotation (RotationLike, optional): angles to rotate about axes. Defaults to (0, 0, 0).
-        align (Union[Align, tuple[Align, Align, Align]], optional): align min, center,
+        align (Align | tuple[Align, Align, Align] | None, optional): align min, center,
             or max of object. Defaults to None.
         mode (Mode, optional): combination mode. Defaults to Mode.ADD.
     """
@@ -57,7 +56,7 @@ def __init__(
         self,
         part: Part | Solid,
         rotation: RotationLike = (0, 0, 0),
-        align: Align | tuple[Align, Align, Align] = None,
+        align: Align | tuple[Align, Align, Align] | None = None,
         mode: Mode = Mode.ADD,
     ):
         if align is not None:
@@ -66,7 +65,7 @@ def __init__(
             offset = bbox.to_align_offset(align)
             part.move(Location(offset))
 
-        context: BuildPart = BuildPart._get_context(self, log=False)
+        context: BuildPart | None = BuildPart._get_context(self, log=False)
         rotate = Rotation(*rotation) if isinstance(rotation, tuple) else rotation
         self.rotation = rotate
         if context is None:
@@ -111,7 +110,7 @@ class Box(BasePartObject):
         width (float): box size
         height (float): box size
         rotation (RotationLike, optional): angles to rotate about axes. Defaults to (0, 0, 0).
-        align (Union[Align, tuple[Align, Align, Align]], optional): align min, center,
+        align (Align | tuple[Align, Align, Align] | None, optional): align min, center,
             or max of object. Defaults to (Align.CENTER, Align.CENTER, Align.CENTER).
         mode (Mode, optional): combine mode. Defaults to Mode.ADD.
     """
@@ -131,7 +130,7 @@ def __init__(
         ),
         mode: Mode = Mode.ADD,
     ):
-        context: BuildPart = BuildPart._get_context(self)
+        context: BuildPart | None = BuildPart._get_context(self)
         validate_inputs(context, self)
 
         self.length = length
@@ -156,7 +155,7 @@ class Cone(BasePartObject):
         height (float): cone size
         arc_size (float, optional): angular size of cone. Defaults to 360.
         rotation (RotationLike, optional): angles to rotate about axes. Defaults to (0, 0, 0).
-        align (Union[Align, tuple[Align, Align, Align]], optional): align min, center,
+        align (Align | tuple[Align, Align, Align] | None, optional): align min, center,
             or max of object. Defaults to (Align.CENTER, Align.CENTER, Align.CENTER).
         mode (Mode, optional): combine mode. Defaults to Mode.ADD.
     """
@@ -177,7 +176,7 @@ def __init__(
         ),
         mode: Mode = Mode.ADD,
     ):
-        context: BuildPart = BuildPart._get_context(self)
+        context: BuildPart | None = BuildPart._get_context(self)
         validate_inputs(context, self)
 
         self.bottom_radius = bottom_radius
@@ -218,10 +217,10 @@ def __init__(
         radius: float,
         counter_bore_radius: float,
         counter_bore_depth: float,
-        depth: float = None,
+        depth: float | None = None,
         mode: Mode = Mode.SUBTRACT,
     ):
-        context: BuildPart = BuildPart._get_context(self)
+        context: BuildPart | None = BuildPart._get_context(self)
         validate_inputs(context, self)
 
         self.radius = radius
@@ -235,7 +234,7 @@ def __init__(
             raise ValueError("No depth provided")
         self.mode = mode
 
-        solid = Solid.make_cylinder(
+        fused = Solid.make_cylinder(
             radius, self.hole_depth, Plane(origin=(0, 0, 0), z_dir=(0, 0, -1))
         ).fuse(
             Solid.make_cylinder(
@@ -244,6 +243,10 @@ def __init__(
                 Plane((0, 0, -counter_bore_depth)),
             )
         )
+        if isinstance(fused, ShapeList):
+            solid = Part(fused)
+        else:
+            solid = fused
         super().__init__(part=solid, rotation=(0, 0, 0), mode=mode)
 
 
@@ -266,11 +269,11 @@ def __init__(
         self,
         radius: float,
         counter_sink_radius: float,
-        depth: float = None,
+        depth: float | None = None,
         counter_sink_angle: float = 82,  # Common tip angle
         mode: Mode = Mode.SUBTRACT,
     ):
-        context: BuildPart = BuildPart._get_context(self)
+        context: BuildPart | None = BuildPart._get_context(self)
         validate_inputs(context, self)
 
         self.radius = radius
@@ -285,7 +288,7 @@ def __init__(
         self.mode = mode
         cone_height = counter_sink_radius / tan(radians(counter_sink_angle / 2.0))
 
-        solid = Solid.make_cylinder(
+        fused = Solid.make_cylinder(
             radius, self.hole_depth, Plane(origin=(0, 0, 0), z_dir=(0, 0, -1))
         ).fuse(
             Solid.make_cone(
@@ -296,6 +299,11 @@ def __init__(
             ),
             Solid.make_cylinder(counter_sink_radius, self.hole_depth),
         )
+        if isinstance(fused, ShapeList):
+            solid = Part(fused)
+        else:
+            solid = fused
+
         super().__init__(part=solid, rotation=(0, 0, 0), mode=mode)
 
 
@@ -309,7 +317,7 @@ class Cylinder(BasePartObject):
         height (float): cylinder size
         arc_size (float, optional): angular size of cone. Defaults to 360.
         rotation (RotationLike, optional): angles to rotate about axes. Defaults to (0, 0, 0).
-        align (Union[Align, tuple[Align, Align, Align]], optional): align min, center,
+        align (Align | tuple[Align, Align, Align] | None, optional): align min, center,
             or max of object. Defaults to (Align.CENTER, Align.CENTER, Align.CENTER).
         mode (Mode, optional): combine mode. Defaults to Mode.ADD.
     """
@@ -329,7 +337,7 @@ def __init__(
         ),
         mode: Mode = Mode.ADD,
     ):
-        context: BuildPart = BuildPart._get_context(self)
+        context: BuildPart | None = BuildPart._get_context(self)
         validate_inputs(context, self)
 
         self.radius = radius
@@ -363,10 +371,10 @@ class Hole(BasePartObject):
     def __init__(
         self,
         radius: float,
-        depth: float = None,
+        depth: float | None = None,
         mode: Mode = Mode.SUBTRACT,
     ):
-        context: BuildPart = BuildPart._get_context(self)
+        context: BuildPart | None = BuildPart._get_context(self)
         validate_inputs(context, self)
 
         self.radius = radius
@@ -405,7 +413,7 @@ class Sphere(BasePartObject):
         arc_size2 (float, optional): angular size of sphere. Defaults to 90.
         arc_size3 (float, optional): angular size of sphere. Defaults to 360.
         rotation (RotationLike, optional): angles to rotate about axes. Defaults to (0, 0, 0).
-        align (Union[Align, tuple[Align, Align, Align]], optional): align min, center,
+        align (Align | tuple[Align, Align, Align] | None, optional): align min, center,
             or max of object. Defaults to (Align.CENTER, Align.CENTER, Align.CENTER).
         mode (Mode, optional): combine mode. Defaults to Mode.ADD.
     """
@@ -426,7 +434,7 @@ def __init__(
         ),
         mode: Mode = Mode.ADD,
     ):
-        context: BuildPart = BuildPart._get_context(self)
+        context: BuildPart | None = BuildPart._get_context(self)
         validate_inputs(context, self)
 
         self.radius = radius
@@ -458,7 +466,7 @@ class Torus(BasePartObject):
         major_arc_size (float, optional): angular size of torus. Defaults to 0.
         minor_arc_size (float, optional): angular size or torus. Defaults to 360.
         rotation (RotationLike, optional): angles to rotate about axes. Defaults to (0, 0, 0).
-        align (Union[Align, tuple[Align, Align, Align]], optional): align min, center,
+        align (Align | tuple[Align, Align, Align] | None, optional): align min, center,
             or max of object. Defaults to (Align.CENTER, Align.CENTER, Align.CENTER).
         mode (Mode, optional): combine mode. Defaults to Mode.ADD.
     """
@@ -480,7 +488,7 @@ def __init__(
         ),
         mode: Mode = Mode.ADD,
     ):
-        context: BuildPart = BuildPart._get_context(self)
+        context: BuildPart | None = BuildPart._get_context(self)
         validate_inputs(context, self)
 
         self.major_radius = major_radius
@@ -516,7 +524,7 @@ class Wedge(BasePartObject):
         xmax (float): maximum X location
         zmax (float): maximum Z location
         rotation (RotationLike, optional): angles to rotate about axes. Defaults to (0, 0, 0).
-        align (Union[Align, tuple[Align, Align, Align]], optional): align min, center,
+        align (Align | tuple[Align, Align, Align] | None, optional): align min, center,
             or max of object. Defaults to (Align.CENTER, Align.CENTER, Align.CENTER).
         mode (Mode, optional): combine mode. Defaults to Mode.ADD.
     """
@@ -540,7 +548,7 @@ def __init__(
         ),
         mode: Mode = Mode.ADD,
     ):
-        context: BuildPart = BuildPart._get_context(self)
+        context: BuildPart | None = BuildPart._get_context(self)
         validate_inputs(context, self)
 
         if any([value <= 0 for value in [xsize, ysize, zsize]]):
diff --git a/src/build123d/objects_sketch.py b/src/build123d/objects_sketch.py
index a6689dae..65771d23 100644
--- a/src/build123d/objects_sketch.py
+++ b/src/build123d/objects_sketch.py
@@ -31,7 +31,7 @@
 import trianglesolver
 
 from math import cos, degrees, pi, radians, sin, tan
-from typing import Union
+from typing import cast
 
 from collections.abc import Iterable
 
@@ -85,7 +85,7 @@ def __init__(
             align = tuplify(align, 2)
             obj.move(Location(obj.bounding_box().to_align_offset(align)))
 
-        context: BuildSketch = BuildSketch._get_context(self, log=False)
+        context: BuildSketch | None = BuildSketch._get_context(self, log=False)
         if context is None:
             new_faces = obj.moved(Rotation(0, 0, rotation)).faces()
 
@@ -95,11 +95,11 @@ def __init__(
 
             obj = obj.moved(Rotation(0, 0, rotation))
 
-            new_faces = [
+            new_faces = ShapeList(
                 face.moved(location)
                 for face in obj.faces()
                 for location in LocationList._get_context().local_locations
-            ]
+            )
             if isinstance(context, BuildSketch):
                 context._add_to_context(*new_faces, mode=mode)
 
@@ -126,7 +126,7 @@ def __init__(
         align: Align | tuple[Align, Align] | None = (Align.CENTER, Align.CENTER),
         mode: Mode = Mode.ADD,
     ):
-        context = BuildSketch._get_context(self)
+        context: BuildSketch | None = BuildSketch._get_context(self)
         validate_inputs(context, self)
 
         self.radius = radius
@@ -160,7 +160,7 @@ def __init__(
         align: Align | tuple[Align, Align] | None = (Align.CENTER, Align.CENTER),
         mode: Mode = Mode.ADD,
     ):
-        context = BuildSketch._get_context(self)
+        context: BuildSketch | None = BuildSketch._get_context(self)
         validate_inputs(context, self)
 
         self.x_radius = x_radius
@@ -199,7 +199,7 @@ def __init__(
         align: Align | tuple[Align, Align] | None = (Align.CENTER, Align.CENTER),
         mode: Mode = Mode.ADD,
     ):
-        context = BuildSketch._get_context(self)
+        context: BuildSketch | None = BuildSketch._get_context(self)
         validate_inputs(context, self)
 
         flattened_pts = flatten_sequence(*pts)
@@ -235,7 +235,7 @@ def __init__(
         align: Align | tuple[Align, Align] | None = (Align.CENTER, Align.CENTER),
         mode: Mode = Mode.ADD,
     ):
-        context = BuildSketch._get_context(self)
+        context: BuildSketch | None = BuildSketch._get_context(self)
         validate_inputs(context, self)
 
         self.width = width
@@ -272,7 +272,7 @@ def __init__(
         align: Align | tuple[Align, Align] | None = (Align.CENTER, Align.CENTER),
         mode: Mode = Mode.ADD,
     ):
-        context = BuildSketch._get_context(self)
+        context: BuildSketch | None = BuildSketch._get_context(self)
         validate_inputs(context, self)
 
         if width <= 2 * radius or height <= 2 * radius:
@@ -317,7 +317,7 @@ def __init__(
         mode: Mode = Mode.ADD,
     ):
         # pylint: disable=too-many-locals
-        context = BuildSketch._get_context(self)
+        context: BuildSketch | None = BuildSketch._get_context(self)
         validate_inputs(context, self)
 
         if side_count < 3:
@@ -381,7 +381,7 @@ def __init__(
         rotation: float = 0,
         mode: Mode = Mode.ADD,
     ):
-        context = BuildSketch._get_context(self)
+        context: BuildSketch | None = BuildSketch._get_context(self)
         validate_inputs(context, self)
 
         self.arc = arc
@@ -417,7 +417,7 @@ def __init__(
         rotation: float = 0,
         mode: Mode = Mode.ADD,
     ):
-        context = BuildSketch._get_context(self)
+        context: BuildSketch | None = BuildSketch._get_context(self)
         validate_inputs(context, self)
 
         center_v = Vector(center)
@@ -472,7 +472,7 @@ def __init__(
                 f"Requires center_separation > 0. Got: {center_separation=}"
             )
 
-        context = BuildSketch._get_context(self)
+        context: BuildSketch | None = BuildSketch._get_context(self)
         validate_inputs(context, self)
 
         self.center_separation = center_separation
@@ -518,14 +518,14 @@ def __init__(
                 f"Slot requires that width > height. Got: {width=}, {height=}"
             )
 
-        context = BuildSketch._get_context(self)
+        context: BuildSketch | None = BuildSketch._get_context(self)
         validate_inputs(context, self)
 
         self.width = width
         self.slot_height = height
 
         if width != height:
-            face: Face | None = Face(
+            face = Face(
                 Wire(
                     [
                         Edge.make_line(Vector(-width / 2 + height / 2, 0, 0), Vector()),
@@ -534,7 +534,7 @@ def __init__(
                 ).offset_2d(height / 2)
             )
         else:
-            face = Circle(width / 2, mode=mode).face()
+            face = cast(Face, Circle(width / 2, mode=mode).face())
         super().__init__(face, rotation, align, mode)
 
 
@@ -574,7 +574,7 @@ def __init__(
         rotation: float = 0.0,
         mode: Mode = Mode.ADD,
     ):
-        context = BuildSketch._get_context(self)
+        context: BuildSketch | None = BuildSketch._get_context(self)
         validate_inputs(context, self)
 
         self.txt = txt
@@ -633,7 +633,7 @@ def __init__(
         align: Align | tuple[Align, Align] | None = (Align.CENTER, Align.CENTER),
         mode: Mode = Mode.ADD,
     ):
-        context = BuildSketch._get_context(self)
+        context: BuildSketch | None = BuildSketch._get_context(self)
         validate_inputs(context, self)
 
         right_side_angle = left_side_angle if not right_side_angle else right_side_angle
@@ -720,7 +720,7 @@ def __init__(
         rotation: float = 0,
         mode: Mode = Mode.ADD,
     ):
-        context = BuildSketch._get_context(self)
+        context: BuildSketch | None = BuildSketch._get_context(self)
         validate_inputs(context, self)
 
         if [v is None for v in [a, b, c]].count(True) == 3 or [
diff --git a/src/build123d/operations_generic.py b/src/build123d/operations_generic.py
index 67370c58..2deeeaa8 100644
--- a/src/build123d/operations_generic.py
+++ b/src/build123d/operations_generic.py
@@ -30,7 +30,7 @@
 import copy
 import logging
 from math import radians, tan
-from typing import Union
+from typing import cast, TypeAlias
 
 from collections.abc import Iterable
 
@@ -78,13 +78,13 @@
 logging.getLogger("build123d").addHandler(logging.NullHandler())
 logger = logging.getLogger("build123d")
 
-#:TypeVar("AddType"): Type of objects which can be added to a builder
-AddType = Union[Edge, Wire, Face, Solid, Compound, Builder]
+AddType: TypeAlias = Edge | Wire | Face | Solid | Compound | Builder
+"""Type of objects which can be added to a builder"""
 
 
 def add(
     objects: AddType | Iterable[AddType],
-    rotation: float | RotationLike = None,
+    rotation: float | RotationLike | None = None,
     clean: bool = True,
     mode: Mode = Mode.ADD,
 ) -> Compound:
@@ -101,22 +101,28 @@ def add(
         Edges and Wires are added to line.
 
     Args:
-        objects (Union[Edge, Wire, Face, Solid, Compound]  or Iterable of): objects to add
-        rotation (Union[float, RotationLike], optional): rotation angle for sketch,
+        objects (Edge |  Wire |  Face |  Solid |  Compound  or Iterable of): objects to add
+        rotation (float |  RotationLike, optional): rotation angle for sketch,
             rotation about each axis for part. Defaults to None.
         clean (bool, optional): Remove extraneous internal structure. Defaults to True.
        mode (Mode, optional): combine mode. Defaults to Mode.ADD.
     """
-    context: Builder = Builder._get_context(None)
+    context: Builder | None = Builder._get_context(None)
     if context is None:
         raise RuntimeError("Add must have an active builder context")
 
-    object_iter = objects if isinstance(objects, Iterable) else [objects]
+    if isinstance(objects, Iterable) and not isinstance(objects, Compound):
+        object_list = list(objects)
+    else:
+        object_list = [objects]
     object_iter = [
-        obj.unwrap(fully=False) if isinstance(obj, Compound) else obj
-        for obj in object_iter
+        (
+            obj.unwrap(fully=False)
+            if isinstance(obj, Compound)
+            else obj._obj if isinstance(obj, Builder) else obj
+        )
+        for obj in object_list
     ]
-    object_iter = [obj._obj if isinstance(obj, Builder) else obj for obj in object_iter]
 
     validate_inputs(context, "add", object_iter)
 
@@ -201,7 +207,7 @@ def add(
 
 
 def bounding_box(
-    objects: Shape | Iterable[Shape] = None,
+    objects: Shape | Iterable[Shape] | None = None,
     mode: Mode = Mode.PRIVATE,
 ) -> Sketch | Part:
     """Generic Operation: Add Bounding Box
@@ -214,7 +220,7 @@ def bounding_box(
         objects (Shape or Iterable of): objects to create bbox for
         mode (Mode, optional): combination mode. Defaults to Mode.ADD.
     """
-    context: Builder = Builder._get_context("bounding_box")
+    context: Builder | None = Builder._get_context("bounding_box")
 
     if objects is None:
         if context is None or context is not None and context._obj is None:
@@ -261,16 +267,16 @@ def bounding_box(
     return Part(Compound(new_objects).wrapped)
 
 
-#:TypeVar("ChamferFilletType"): Type of objects which can be chamfered or filleted
-ChamferFilletType = Union[Edge, Vertex]
+ChamferFilletType: TypeAlias = Edge | Vertex
+"""Type of objects which can be chamfered or filleted"""
 
 
 def chamfer(
     objects: ChamferFilletType | Iterable[ChamferFilletType],
     length: float,
-    length2: float = None,
-    angle: float = None,
-    reference: Edge | Face = None,
+    length2: float | None = None,
+    angle: float | None = None,
+    reference: Edge | Face | None = None,
 ) -> Sketch | Part:
     """Generic Operation: chamfer
 
@@ -279,11 +285,11 @@ def chamfer(
     Chamfer the given sequence of edges or vertices.
 
     Args:
-        objects (Union[Edge,Vertex]  or Iterable of): edges or vertices to chamfer
+        objects (Edge | Vertex  or Iterable of): edges or vertices to chamfer
         length (float): chamfer size
         length2 (float, optional): asymmetric chamfer size. Defaults to None.
         angle (float, optional): chamfer angle in degrees. Defaults to None.
-        reference (Union[Edge,Face]): identifies the side where length is measured. Edge(s) must
+        reference (Edge | Face): identifies the side where length is measured. Edge(s) must
             be part of the face. Vertex/Vertices must be part of edge
 
     Raises:
@@ -293,7 +299,7 @@ def chamfer(
         ValueError: Only one of length2 or angle should be provided
         ValueError: reference can only be used in conjunction with length2 or angle
     """
-    context: Builder = Builder._get_context("chamfer")
+    context: Builder | None = Builder._get_context("chamfer")
     if length2 and angle:
         raise ValueError("Only one of length2 or angle should be provided")
 
@@ -367,24 +373,28 @@ def chamfer(
             raise ValueError("1D fillet operation takes only Vertices")
         # Remove any end vertices as these can't be filleted
         if not target.is_closed:
-            object_list = filter(
-                lambda v: not (
-                    isclose_b(
-                        (Vector(*v.to_tuple()) - target.position_at(0)).length,
-                        0.0,
-                    )
-                    or isclose_b(
-                        (Vector(*v.to_tuple()) - target.position_at(1)).length,
-                        0.0,
-                    )
-                ),
-                object_list,
+            object_list = ShapeList(
+                filter(
+                    lambda v: not (
+                        isclose_b(
+                            (Vector(*v.to_tuple()) - target.position_at(0)).length,
+                            0.0,
+                        )
+                        or isclose_b(
+                            (Vector(*v.to_tuple()) - target.position_at(1)).length,
+                            0.0,
+                        )
+                    ),
+                    object_list,
+                )
             )
         new_wire = target.chamfer_2d(length, length2, object_list, reference)
         if context is not None:
             context._add_to_context(new_wire, mode=Mode.REPLACE)
         return new_wire
 
+    raise ValueError("Invalid object dimension")
+
 
 def fillet(
     objects: ChamferFilletType | Iterable[ChamferFilletType],
@@ -398,7 +408,7 @@ def fillet(
     either end of an open line will be automatically skipped.
 
     Args:
-        objects (Union[Edge,Vertex] or Iterable of): edges or vertices to fillet
+        objects (Edge | Vertex or Iterable of): edges or vertices to fillet
         radius (float): fillet size - must be less than 1/2 local width
 
     Raises:
@@ -407,7 +417,7 @@ def fillet(
         ValueError: objects must be Vertices
         ValueError: nothing to fillet
     """
-    context: Builder = Builder._get_context("fillet")
+    context: Builder | None = Builder._get_context("fillet")
     if (objects is None and context is None) or (
         objects is None and context is not None and context._obj is None
     ):
@@ -466,31 +476,35 @@ def fillet(
             raise ValueError("1D fillet operation takes only Vertices")
         # Remove any end vertices as these can't be filleted
         if not target.is_closed:
-            object_list = filter(
-                lambda v: not (
-                    isclose_b(
-                        (Vector(*v.to_tuple()) - target.position_at(0)).length,
-                        0.0,
-                    )
-                    or isclose_b(
-                        (Vector(*v.to_tuple()) - target.position_at(1)).length,
-                        0.0,
-                    )
-                ),
-                object_list,
+            object_list = ShapeList(
+                filter(
+                    lambda v: not (
+                        isclose_b(
+                            (Vector(*v.to_tuple()) - target.position_at(0)).length,
+                            0.0,
+                        )
+                        or isclose_b(
+                            (Vector(*v.to_tuple()) - target.position_at(1)).length,
+                            0.0,
+                        )
+                    ),
+                    object_list,
+                )
             )
         new_wire = target.fillet_2d(radius, object_list)
         if context is not None:
             context._add_to_context(new_wire, mode=Mode.REPLACE)
         return new_wire
 
+    raise ValueError("Invalid object dimension")
 
-#:TypeVar("MirrorType"): Type of objects which can be mirrored
-MirrorType = Union[Edge, Wire, Face, Compound, Curve, Sketch, Part]
+
+MirrorType: TypeAlias = Edge | Wire | Face | Compound | Curve | Sketch | Part
+"""Type of objects which can be mirrored"""
 
 
 def mirror(
-    objects: MirrorType | Iterable[MirrorType] = None,
+    objects: MirrorType | Iterable[MirrorType] | None = None,
     about: Plane = Plane.XZ,
     mode: Mode = Mode.ADD,
 ) -> Curve | Sketch | Part | Compound:
@@ -501,15 +515,18 @@ def mirror(
     Mirror a sequence of objects over the given plane.
 
     Args:
-        objects (Union[Edge, Face,Compound]  or Iterable of): objects to mirror
+        objects (Edge |  Face | Compound  or Iterable of): objects to mirror
         about (Plane, optional): reference plane. Defaults to "XZ".
         mode (Mode, optional): combination mode. Defaults to Mode.ADD.
 
     Raises:
         ValueError: missing objects
     """
-    context: Builder = Builder._get_context("mirror")
-    object_list = objects if isinstance(objects, Iterable) else [objects]
+    context: Builder | None = Builder._get_context("mirror")
+    if isinstance(objects, Iterable) and not isinstance(objects, Compound):
+        object_list = list(objects)
+    else:
+        object_list = [objects]
 
     if objects is None:
         if context is None or context is not None and context._obj is None:
@@ -535,18 +552,18 @@ def mirror(
     return mirrored_compound
 
 
-#:TypeVar("OffsetType"): Type of objects which can be offset
-OffsetType = Union[Edge, Face, Solid, Compound]
+OffsetType: TypeAlias = Edge | Face | Solid | Compound
+"""Type of objects which can be offset"""
 
 
 def offset(
-    objects: OffsetType | Iterable[OffsetType] = None,
+    objects: OffsetType | Iterable[OffsetType] | None = None,
     amount: float = 0,
-    openings: Face | list[Face] = None,
+    openings: Face | list[Face] | None = None,
     kind: Kind = Kind.ARC,
     side: Side = Side.BOTH,
     closed: bool = True,
-    min_edge_length: float = None,
+    min_edge_length: float | None = None,
     mode: Mode = Mode.REPLACE,
 ) -> Curve | Sketch | Part | Compound:
     """Generic Operation: offset
@@ -559,7 +576,7 @@ def offset(
     a hollow box with no lid.
 
     Args:
-        objects (Union[Edge, Face, Solid, Compound]  or Iterable of): objects to offset
+        objects (Edge |  Face |  Solid |  Compound  or Iterable of): objects to offset
         amount (float): positive values external, negative internal
         openings (list[Face], optional), sequence of faces to open in part.
             Defaults to None.
@@ -575,7 +592,7 @@ def offset(
         ValueError: missing objects
         ValueError: Invalid object type
     """
-    context: Builder = Builder._get_context("offset")
+    context: Builder | None = Builder._get_context("offset")
 
     if objects is None:
         if context is None or context is not None and context._obj is None:
@@ -624,15 +641,19 @@ def offset(
                 pass
         # inner wires may go beyond the outer wire so subtract faces
         new_face = Face(outer_wire)
-        if inner_wires:
-            inner_faces = [Face(w) for w in inner_wires]
-            new_face = new_face.cut(*inner_faces)
-            if isinstance(new_face, Compound):
-                new_face = new_face.unwrap(fully=True)
-
         if (new_face.normal_at() - face.normal_at()).length > 0.001:
             new_face = -new_face
-        new_faces.append(new_face)
+        if inner_wires:
+            inner_faces = [Face(w) for w in inner_wires]
+            subtraction = new_face.cut(*inner_faces)
+            if isinstance(subtraction, Compound):
+                new_faces.append(new_face.unwrap(fully=True))
+            elif isinstance(subtraction, ShapeList):
+                new_faces.extend(subtraction)
+            else:
+                new_faces.append(subtraction)
+        else:
+            new_faces.append(new_face)
     if edges:
         if len(edges) == 1 and edges[0].geom_type == GeomType.LINE:
             new_wires = [
@@ -679,14 +700,14 @@ def offset(
     return offset_compound
 
 
-#:TypeVar("ProjectType"): Type of objects which can be projected
-ProjectType = Union[Edge, Face, Wire, Vector, Vertex]
+ProjectType: TypeAlias = Edge | Face | Wire | Vector | Vertex
+"""Type of objects which can be projected"""
 
 
 def project(
-    objects: ProjectType | Iterable[ProjectType] = None,
-    workplane: Plane = None,
-    target: Solid | Compound | Part = None,
+    objects: ProjectType | Iterable[ProjectType] | None = None,
+    workplane: Plane | None = None,
+    target: Solid | Compound | Part | None = None,
     mode: Mode = Mode.ADD,
 ) -> Curve | Sketch | Compound | ShapeList[Vector]:
     """Generic Operation: project
@@ -704,7 +725,7 @@ def project(
     BuildSketch and Edge/Wires into BuildLine.
 
     Args:
-        objects (Union[Edge, Face, Wire, VectorLike, Vertex] or Iterable of):
+        objects (Edge |  Face |  Wire |  VectorLike |  Vertex or Iterable of):
             objects or points to project
         workplane (Plane, optional): screen workplane
         mode (Mode, optional): combination mode. Defaults to Mode.ADD.
@@ -716,7 +737,7 @@ def project(
         ValueError: Edges, wires and points can only be projected in PRIVATE mode
         RuntimeError: BuildPart doesn't have a project operation
     """
-    context: Builder = Builder._get_context("project")
+    context: Builder | None = Builder._get_context("project")
 
     if isinstance(objects, GroupBy):
         raise ValueError("project doesn't accept group_by, did you miss [n]?")
@@ -742,8 +763,8 @@ def project(
     ]
     object_size = Compound(children=shape_list).bounding_box(optimal=False).diagonal
 
-    point_list = [o for o in object_list if isinstance(o, (Vector, Vertex))]
-    point_list = [Vector(pnt) for pnt in point_list]
+    vct_vrt_list = [o for o in object_list if isinstance(o, (Vector, Vertex))]
+    point_list = [Vector(pnt) for pnt in vct_vrt_list]
     face_list = [o for o in object_list if isinstance(o, Face)]
     line_list = [o for o in object_list if isinstance(o, (Edge, Wire))]
 
@@ -764,6 +785,7 @@ def project(
                 raise ValueError(
                     "Edges, wires and points can only be projected in PRIVATE mode"
                 )
+    working_plane = cast(Plane, workplane)
 
     # BuildLine and BuildSketch are from target to workplane while BuildPart is
     # from workplane to target so the projection direction needs to be flipped
@@ -775,7 +797,7 @@ def project(
             target = context._obj
         projection_flip = -1
     else:
-        target = Face.make_rect(3 * object_size, 3 * object_size, plane=workplane)
+        target = Face.make_rect(3 * object_size, 3 * object_size, plane=working_plane)
 
     validate_inputs(context, "project")
 
@@ -783,37 +805,39 @@ def project(
     obj: Shape
     for obj in face_list + line_list:
         obj_to_screen = (target.center() - obj.center()).normalized()
-        if workplane.from_local_coords(obj_to_screen).Z < 0:
-            projection_direction = -workplane.z_dir * projection_flip
+        if working_plane.from_local_coords(obj_to_screen).Z < 0:
+            projection_direction = -working_plane.z_dir * projection_flip
         else:
-            projection_direction = workplane.z_dir * projection_flip
+            projection_direction = working_plane.z_dir * projection_flip
         projection = obj.project_to_shape(target, projection_direction)
         if projection:
             if isinstance(context, BuildSketch):
                 projected_shapes.extend(
-                    [workplane.to_local_coords(p) for p in projection]
+                    [working_plane.to_local_coords(p) for p in projection]
                 )
             elif isinstance(context, BuildLine):
                 projected_shapes.extend(projection)
             else:  # BuildPart
                 projected_shapes.append(projection[0])
 
-    projected_points = []
+    projected_points: ShapeList[Vector] = ShapeList()
     for pnt in point_list:
-        pnt_to_target = (workplane.origin - pnt).normalized()
-        if workplane.from_local_coords(pnt_to_target).Z < 0:
-            projection_axis = -Axis(pnt, workplane.z_dir * projection_flip)
+        pnt_to_target = (working_plane.origin - pnt).normalized()
+        if working_plane.from_local_coords(pnt_to_target).Z < 0:
+            projection_axis = -Axis(pnt, working_plane.z_dir * projection_flip)
         else:
-            projection_axis = Axis(pnt, workplane.z_dir * projection_flip)
-        projection = workplane.to_local_coords(workplane.intersect(projection_axis))
-        if projection is not None:
-            projected_points.append(projection)
+            projection_axis = Axis(pnt, working_plane.z_dir * projection_flip)
+        intersection = working_plane.intersect(projection_axis)
+        if isinstance(intersection, Axis):
+            raise RuntimeError("working_plane and projection_axis are parallel")
+        if intersection is not None:
+            projected_points.append(working_plane.to_local_coords(intersection))
 
     if context is not None:
         context._add_to_context(*projected_shapes, mode=mode)
 
     if projected_points:
-        result = ShapeList(projected_points)
+        result = projected_points
     else:
         result = Compound(projected_shapes)
         if all([obj._dim == 2 for obj in object_list]):
@@ -825,7 +849,7 @@ def project(
 
 
 def scale(
-    objects: Shape | Iterable[Shape] = None,
+    objects: Shape | Iterable[Shape] | None = None,
     by: float | tuple[float, float, float] = 1,
     mode: Mode = Mode.REPLACE,
 ) -> Curve | Sketch | Part | Compound:
@@ -838,14 +862,14 @@ def scale(
     line, circle, etc.
 
     Args:
-        objects (Union[Edge, Face, Compound, Solid] or Iterable of): objects to scale
-        by (Union[float, tuple[float, float, float]]): scale factor
+        objects (Edge |  Face |  Compound |  Solid or Iterable of): objects to scale
+        by (float | tuple[float, float, float]): scale factor
         mode (Mode, optional): combination mode. Defaults to Mode.REPLACE.
 
     Raises:
         ValueError: missing objects
     """
-    context: Builder = Builder._get_context("scale")
+    context: Builder | None = Builder._get_context("scale")
 
     if objects is None:
         if context is None or context is not None and context._obj is None:
@@ -863,12 +887,12 @@ def scale(
         and len(by) == 3
         and all(isinstance(s, (int, float)) for s in by)
     ):
-        factor = Vector(by)
+        by_vector = Vector(by)
         scale_matrix = Matrix(
             [
-                [factor.X, 0.0, 0.0, 0.0],
-                [0.0, factor.Y, 0.0, 0.0],
-                [0.0, 0.0, factor.Z, 0.0],
+                [by_vector.X, 0.0, 0.0, 0.0],
+                [0.0, by_vector.Y, 0.0, 0.0],
+                [0.0, 0.0, by_vector.Z, 0.0],
                 [0.0, 0.0, 0.0, 1.0],
             ]
         )
@@ -877,9 +901,12 @@ def scale(
 
     new_objects = []
     for obj in object_list:
+        if obj is None:
+            continue
         current_location = obj.location
+        assert current_location is not None
         obj_at_origin = obj.located(Location(Vector()))
-        if isinstance(factor, float):
+        if isinstance(by, (int, float)):
             new_object = obj_at_origin.scale(factor).locate(current_location)
         else:
             new_object = obj_at_origin.transform_geometry(scale_matrix).locate(
@@ -900,12 +927,12 @@ def scale(
     return scale_compound.unwrap(fully=False)
 
 
-#:TypeVar("SplitType"): Type of objects which can be offset
-SplitType = Union[Edge, Wire, Face, Solid]
+SplitType: TypeAlias = Edge | Wire | Face | Solid
+"""Type of objects which can be split"""
 
 
 def split(
-    objects: SplitType | Iterable[SplitType] = None,
+    objects: SplitType | Iterable[SplitType] | None = None,
     bisect_by: Plane | Face | Shell = Plane.XZ,
     keep: Keep = Keep.TOP,
     mode: Mode = Mode.REPLACE,
@@ -917,8 +944,8 @@ def split(
     Bisect object with plane and keep either top, bottom or both.
 
     Args:
-        objects (Union[Edge, Wire, Face, Solid] or Iterable of), objects to split
-        bisect_by (Union[Plane, Face], optional): plane to segment part.
+        objects (Edge |  Wire |  Face |  Solid or Iterable of), objects to split
+        bisect_by (Plane |  Face, optional): plane to segment part.
             Defaults to Plane.XZ.
         keep (Keep, optional): selector for which segment to keep. Defaults to Keep.TOP.
         mode (Mode, optional): combination mode. Defaults to Mode.REPLACE.
@@ -926,7 +953,7 @@ def split(
     Raises:
         ValueError: missing objects
     """
-    context: Builder = Builder._get_context("split")
+    context: Builder | None = Builder._get_context("split")
 
     if objects is None:
         if context is None or context is not None and context._obj is None:
@@ -937,7 +964,7 @@ def split(
 
     validate_inputs(context, "split", object_list)
 
-    new_objects = []
+    new_objects: list[SplitType] = []
     for obj in object_list:
         bottom = None
         if keep == Keep.BOTH:
@@ -963,18 +990,18 @@ def split(
     return split_compound
 
 
-#:TypeVar("SweepType"): Type of objects which can be swept
-SweepType = Union[Compound, Edge, Wire, Face, Solid]
+SweepType: TypeAlias = Compound | Edge | Wire | Face | Solid
+"""Type of objects which can be swept"""
 
 
 def sweep(
-    sections: SweepType | Iterable[SweepType] = None,
-    path: Curve | Edge | Wire | Iterable[Edge] = None,
+    sections: SweepType | Iterable[SweepType] | None = None,
+    path: Curve | Edge | Wire | Iterable[Edge] | None = None,
     multisection: bool = False,
     is_frenet: bool = False,
     transition: Transition = Transition.TRANSFORMED,
-    normal: VectorLike = None,
-    binormal: Edge | Wire = None,
+    normal: VectorLike | None = None,
+    binormal: Edge | Wire | None = None,
     clean: bool = True,
     mode: Mode = Mode.ADD,
 ) -> Part | Sketch:
@@ -983,19 +1010,19 @@ def sweep(
     Sweep pending 1D or 2D objects along path.
 
     Args:
-        sections (Union[Compound, Edge, Wire, Face, Solid]): cross sections to sweep into object
-        path (Union[Curve, Edge, Wire], optional): path to follow.
+        sections (Compound |  Edge |  Wire |  Face |  Solid): cross sections to sweep into object
+        path (Curve |  Edge |  Wire, optional): path to follow.
             Defaults to context pending_edges.
         multisection (bool, optional): sweep multiple on path. Defaults to False.
         is_frenet (bool, optional): use frenet algorithm. Defaults to False.
         transition (Transition, optional): discontinuity handling option.
             Defaults to Transition.TRANSFORMED.
         normal (VectorLike, optional): fixed normal. Defaults to None.
-        binormal (Union[Edge, Wire], optional): guide rotation along path. Defaults to None.
+        binormal (Edge |  Wire, optional): guide rotation along path. Defaults to None.
         clean (bool, optional): Remove extraneous internal structure. Defaults to True.
         mode (Mode, optional): combination. Defaults to Mode.ADD.
     """
-    context: Builder = Builder._get_context("sweep")
+    context: Builder | None = Builder._get_context("sweep")
 
     section_list = (
         [*sections] if isinstance(sections, (list, tuple, filter)) else [sections]
@@ -1005,7 +1032,11 @@ def sweep(
     validate_inputs(context, "sweep", section_list)
 
     if path is None:
-        if context is None or context is not None and not context.pending_edges:
+        if (
+            context is None
+            or not isinstance(context, (BuildPart, BuildSketch))
+            or not context.pending_edges
+        ):
             raise ValueError("path must be provided")
         path_wire = Wire(context.pending_edges)
         context.pending_edges = []
@@ -1030,8 +1061,8 @@ def sweep(
         else:
             raise ValueError("No sections provided")
 
-    edge_list = []
-    face_list = []
+    edge_list: list[Edge] = []
+    face_list: list[Face] = []
     for sec in section_list:
         if isinstance(sec, (Curve, Wire, Edge)):
             edge_list.extend(sec.edges())
@@ -1040,6 +1071,7 @@ def sweep(
 
     # sweep to create solids
     new_solids = []
+    binormal_mode: Wire | Vector | None
     if face_list:
         if binormal is None and normal is not None:
             binormal_mode = Vector(normal)
@@ -1066,7 +1098,7 @@ def sweep(
             ]
 
     # sweep to create faces
-    new_faces = []
+    new_faces: list[Face] = []
     if edge_list:
         for sec in section_list:
             swept = Shell.sweep(sec, path_wire, transition)
diff --git a/src/build123d/operations_sketch.py b/src/build123d/operations_sketch.py
index d305b51b..4883be5c 100644
--- a/src/build123d/operations_sketch.py
+++ b/src/build123d/operations_sketch.py
@@ -28,9 +28,9 @@
 """
 
 from __future__ import annotations
-from typing import Union
 
 from collections.abc import Iterable
+from scipy.spatial import Voronoi
 from build123d.build_enums import Mode, SortBy
 from build123d.topology import (
     Compound,
@@ -46,7 +46,6 @@
 from build123d.geometry import Vector, TOLERANCE
 from build123d.build_common import flatten_sequence, validate_inputs
 from build123d.build_sketch import BuildSketch
-from scipy.spatial import Voronoi
 
 
 def full_round(
@@ -77,7 +76,7 @@ def full_round(
         geometric center of the arc, and the third the radius of the arc
 
     """
-    context: BuildSketch = BuildSketch._get_context("full_round")
+    context: BuildSketch | None = BuildSketch._get_context("full_round")
 
     if not isinstance(edge, Edge):
         raise ValueError("A single Edge must be provided")
@@ -108,7 +107,11 @@ def full_round(
     # Refine the largest empty circle center estimate by averaging the best
     # three candidates.  The minimum distance between the edges and this
     # center is the circle radius.
-    best_three = [(float("inf"), None), (float("inf"), None), (float("inf"), None)]
+    best_three: list[tuple[float, int]] = [
+        (float("inf"), int()),
+        (float("inf"), int()),
+        (float("inf"), int()),
+    ]
 
     for i, v in enumerate(voronoi_vertices):
         distances = [edge_group[i].distance_to(v) for i in range(3)]
@@ -125,7 +128,9 @@ def full_round(
 
     # Extract the indices of the best three and average them
     best_indices = [x[1] for x in best_three]
-    voronoi_circle_center = sum(voronoi_vertices[i] for i in best_indices) / 3
+    voronoi_circle_center: Vector = (
+        sum((voronoi_vertices[i] for i in best_indices), Vector(0, 0, 0)) / 3.0
+    )
 
     # Determine where the connected edges intersect with the largest empty circle
     connected_edges_end_points = [
@@ -142,7 +147,7 @@ def full_round(
         for i, e in enumerate(connected_edges)
     ]
     for param in connected_edges_end_params:
-        if not (0.0 < param < 1.0):
+        if not 0.0 < param < 1.0:
             raise ValueError("Invalid geometry to create the end arc")
 
     common_vertex_points = [
@@ -177,7 +182,14 @@ def full_round(
     )
 
     # Recover other edges
-    other_edges = edge.topo_parent.edges() - topo_explore_connected_edges(edge) - [edge]
+    if edge.topo_parent is None:
+        other_edges: ShapeList[Edge] = ShapeList()
+    else:
+        other_edges = (
+            edge.topo_parent.edges()
+            - topo_explore_connected_edges(edge)
+            - ShapeList([edge])
+        )
 
     # Rebuild the face
     # Note that the longest wire must be the perimeter and others holes
@@ -195,7 +207,7 @@ def full_round(
 
 
 def make_face(
-    edges: Edge | Iterable[Edge] = None, mode: Mode = Mode.ADD
+    edges: Edge | Iterable[Edge] | None = None, mode: Mode = Mode.ADD
 ) -> Sketch:
     """Sketch Operation: make_face
 
@@ -206,7 +218,7 @@ def make_face(
             sketch pending edges.
         mode (Mode, optional): combination mode. Defaults to Mode.ADD.
     """
-    context: BuildSketch = BuildSketch._get_context("make_face")
+    context: BuildSketch | None = BuildSketch._get_context("make_face")
 
     if edges is not None:
         outer_edges = flatten_sequence(edges)
@@ -230,7 +242,7 @@ def make_face(
 
 
 def make_hull(
-    edges: Edge | Iterable[Edge] = None, mode: Mode = Mode.ADD
+    edges: Edge | Iterable[Edge] | None = None, mode: Mode = Mode.ADD
 ) -> Sketch:
     """Sketch Operation: make_hull
 
@@ -241,7 +253,7 @@ def make_hull(
             sketch pending edges.
         mode (Mode, optional): combination mode. Defaults to Mode.ADD.
     """
-    context: BuildSketch = BuildSketch._get_context("make_hull")
+    context: BuildSketch | None = BuildSketch._get_context("make_hull")
 
     if edges is not None:
         hull_edges = flatten_sequence(edges)
@@ -268,7 +280,7 @@ def make_hull(
 
 
 def trace(
-    lines: Curve | Edge | Wire | Iterable[Curve | Edge | Wire] = None,
+    lines: Curve | Edge | Wire | Iterable[Curve | Edge | Wire] | None = None,
     line_width: float = 1,
     mode: Mode = Mode.ADD,
 ) -> Sketch:
@@ -277,7 +289,7 @@ def trace(
     Convert edges, wires or pending edges into faces by sweeping a perpendicular line along them.
 
     Args:
-        lines (Union[Curve, Edge, Wire, Iterable[Union[Curve, Edge, Wire]]], optional): lines to
+        lines (Curve | Edge | Wire | Iterable[Curve | Edge | Wire]], optional): lines to
             trace. Defaults to sketch pending edges.
         line_width (float, optional): Defaults to 1.
         mode (Mode, optional): combination mode. Defaults to Mode.ADD.
@@ -288,7 +300,7 @@ def trace(
     Returns:
         Sketch: Traced lines
     """
-    context: BuildSketch = BuildSketch._get_context("trace")
+    context: BuildSketch | None = BuildSketch._get_context("trace")
 
     if lines is not None:
         trace_lines = flatten_sequence(lines)
@@ -298,7 +310,7 @@ def trace(
     else:
         raise ValueError("No objects to trace")
 
-    new_faces = []
+    new_faces: list[Face] = []
     for edge in trace_edges:
         trace_pen = edge.perpendicular_line(line_width, 0)
         new_faces.extend(Face.sweep(trace_pen, edge).faces())
@@ -306,6 +318,7 @@ def trace(
         context._add_to_context(*new_faces, mode=mode)
         context.pending_edges = ShapeList()
 
+    # pylint: disable=no-value-for-parameter
     combined_faces = Face.fuse(*new_faces) if len(new_faces) > 1 else new_faces[0]
     result = (
         Sketch(combined_faces)
diff --git a/src/build123d/topology/composite.py b/src/build123d/topology/composite.py
index 8be2776e..5be6a8fb 100644
--- a/src/build123d/topology/composite.py
+++ b/src/build123d/topology/composite.py
@@ -237,7 +237,7 @@ def make_text(
         font: str = "Arial",
         font_path: str | None = None,
         font_style: FontStyle = FontStyle.REGULAR,
-        align: Align | tuple[Align, Align] = (Align.CENTER, Align.CENTER),
+        align: Align | tuple[Align, Align] | None = (Align.CENTER, Align.CENTER),
         position_on_path: float = 0.0,
         text_path: Edge | Wire | None = None,
     ) -> Compound:
diff --git a/tests/test_exporters.py b/tests/test_exporters.py
index a038057b..f95a92ed 100644
--- a/tests/test_exporters.py
+++ b/tests/test_exporters.py
@@ -29,6 +29,7 @@
     add,
     mirror,
     section,
+    ThreePointArc,
 )
 from build123d.exporters import ExportSVG, ExportDXF, Drawing, LineType
 
@@ -173,6 +174,24 @@ def test_color(self):
         svg.add_shape(sketch)
         svg.write("test-colors.svg")
 
+    def test_svg_small_arc(self):
+        pnts = ((0, 0), (0, 0.000001), (0.000001, 0))
+        small_arc = ThreePointArc(pnts).scale(0.01)
+        with self.assertWarns(UserWarning):
+            svg_exporter = ExportSVG()
+            segments = svg_exporter._circle_segments(small_arc.edges()[0], False)
+            self.assertEqual(len(segments), 0, "Small arc should produce no segments")
+
+    def test_svg_small_ellipse(self):
+        pnts = ((0, 0), (0, 0.000001), (0.000002, 0))
+        small_ellipse = ThreePointArc(pnts).scale(0.01)
+        with self.assertWarns(UserWarning):
+            svg_exporter = ExportSVG()
+            segments = svg_exporter._ellipse_segments(small_ellipse.edges()[0], False)
+            self.assertEqual(
+                len(segments), 0, "Small ellipse should produce no segments"
+            )
+
 
 @pytest.mark.parametrize(
     "format", (Path, fsencode, fsdecode), ids=["path", "bytes", "str"]