diff --git a/layer_shell_preload.md b/layer_shell_preload.md
new file mode 100644
index 0000000..86b5b44
--- /dev/null
+++ b/layer_shell_preload.md
@@ -0,0 +1,22 @@
+# Layer Shell Preload
+`liblayer-shell-preload.so` is a hack to allow arbitrary Wayland apps to use the Layer Shell protocol. It uses the same approach as gtk4-layer-shell, but generalized to work with any `libwayland-client` program. It's designed to be `LD_PRELOAD`ed into pre-built binaries, no recompiling necessary.
+
+There is no officially supported way to use Layer Shell Preload. If it works, it works. If it doesn't work or randomly stops working, that is a you problem. Not a me problem, and definitely not an upstream app dev problem. __Do not report bugs to app or toolkit developers if Layer Shell Preload is involved in any way.__ You're welcome to report bugs here, but I'm likely to ignore or close them (especially it's just "crashes X program").
+
+## Usage
+Run your program with `LD_PRELOAD` set to the path to `liblayer-shell-preload.so`, and use `LAYER_` environment variables to control the layer surface's properties. For example
+```
+$ LD_PRELOAD=/usr/lib/liblayer-shell-preload.so LAYER_ANCHOR='lrb' LAYER_HEIGHT=50 LAYER_EXCLUSIVE=1 LAYER_KEYBOARD=on-demand weston-terminal
+```
+The options are
+| Variable | Values | Use |
+| - | - | - |
+| `LAYER_LAYER` | unset/`o`/`overlay`, `t`/`top`, `b`/`bottom`, `g`/`background` | The layer of the window (overlay and top are over other windows, bottom and background are below them) |
+| `LAYER_ANCHOR` | One or more of the letters `l`, `r`, `t` and `b` in any order, or `0`/unset for none | Which edges of the screen to anchor the surface to |
+| `LAYER_EXCLUSIVE` | unset/`0` or `1` | If to take up space and push other windows out of the way. Only works if anchored to an edge |
+| `LAYER_WIDTH`/`LAYER_HEIGHT` | unset or any number | The preferred width and/or height for the surface when it's not being stretched across the screen |
+| `LAYER_KEYBOARD` | unset/`n`/`none`, `e`/`exclusive` or `o`/`on-demand` | If to allow or lock keyboard focus on the window |
+| `LAYER_NAMESPACE` | unset or any string | The `namespace` property for the layer shell surface, can be used by the Wayland compositor |
+| `LAYER_ALL_SURFACES` | unset/`0` or `1` | By default only the first surface a program creates is a layer surface. With this set they all are. This breaks popups |
+
+Output selection is not yet supported, but could be added in the future.
diff --git a/src/layer-shell-preload.c b/src/layer-shell-preload.c
new file mode 100644
index 0000000..8afee42
--- /dev/null
+++ b/src/layer-shell-preload.c
@@ -0,0 +1,115 @@
+#include "layer-surface.h"
+#include "stdlib.h"
+#include "string.h"
+#include "stdio.h"
+
+static bool has_created_layer_surface = false;
+
+static bool get_bool_from_env(const char* env) {
+    const char* val = getenv(env);
+    if (!val || strcmp(val, "") == 0 || strcmp(val, "0") == 0) {
+        return false;
+    } else if (strcmp(val, "1") == 0) {
+        return true;
+    } else {
+        fprintf(stderr, "Invalid value for %s (expected '1', '0' or unset)", env);
+        exit(1);
+    }
+}
+
+static int get_int_from_env(const char* env) {
+    const char* val = getenv(env);
+    return val ? atoi(val) : 0;
+}
+
+static const char* get_string_from_env(const char* env, const char* fallback) {
+    const char* val = getenv(env);
+    if (val && *val) {
+        return val;
+    } else {
+        return fallback;
+    }
+}
+
+static struct geom_edges_t get_edges_from_env(const char* env) {
+    const char* val = getenv(env);
+    if (!val || strcmp(val, "0") == 0) {
+        return (struct geom_edges_t){0};
+    } else {
+        struct geom_edges_t ret = {0};
+        for (const char* c = val; *c; c++) {
+            switch (*c) {
+                case 'l': ret.left   = true; break;
+                case 'r': ret.right  = true; break;
+                case 't': ret.top    = true; break;
+                case 'b': ret.bottom = true; break;
+                default:
+                    fprintf(stderr, "Invalid character '%c' in %s (expected 'l', 'r', 't' and 'b')", *c, env);
+                    exit(1);
+            }
+        }
+        return ret;
+    }
+}
+
+static enum zwlr_layer_shell_v1_layer get_layer_from_env(const char* env) {
+    const char* val = getenv(env);
+    if (!val || strcmp(val, "") == 0 || strcmp(val, "o") == 0 || strcmp(val, "overlay") == 0) {
+        return ZWLR_LAYER_SHELL_V1_LAYER_OVERLAY;
+    } else if (strcmp(val, "t") == 0 || strcmp(val, "top") == 0) {
+        return ZWLR_LAYER_SHELL_V1_LAYER_TOP;
+    } else if (strcmp(val, "b") == 0 || strcmp(val, "bottom") == 0) {
+        return ZWLR_LAYER_SHELL_V1_LAYER_BOTTOM;
+    } else if (strcmp(val, "g") == 0 || strcmp(val, "background") == 0) {
+        return ZWLR_LAYER_SHELL_V1_LAYER_BACKGROUND;
+    } else {
+        fprintf(stderr, "Invalid value for %s (expected unset/'o'/'overlay', 't'/'top', 'b'/'bottom', 'g'/'background')", env);
+        exit(1);
+    }
+}
+
+static enum zwlr_layer_surface_v1_keyboard_interactivity get_keyboard_interactivity_from_env(const char* env) {
+    const char* val = getenv(env);
+    if (!val || strcmp(val, "") == 0 || strcmp(val, "n") == 0 || strcmp(val, "none") == 0) {
+        return ZWLR_LAYER_SURFACE_V1_KEYBOARD_INTERACTIVITY_NONE;
+    } else if (strcmp(val, "e") == 0 || strcmp(val, "exclusive") == 0) {
+        return ZWLR_LAYER_SURFACE_V1_KEYBOARD_INTERACTIVITY_EXCLUSIVE;
+    } else if (strcmp(val, "o") == 0 || strcmp(val, "on-demand") == 0) {
+        return ZWLR_LAYER_SURFACE_V1_KEYBOARD_INTERACTIVITY_ON_DEMAND;
+    } else {
+        fprintf(stderr, "Invalid value for %s (expected unset/'n'/'none', 'e'/'exclusive' or 'o'/'on-demand')", env);
+        exit(1);
+    }
+}
+
+static struct geom_size_t get_preferred_size(struct layer_surface_t* surface) {
+    (void)surface;
+    return (struct geom_size_t){
+        .width = get_int_from_env("LAYER_WIDTH"),
+        .height = get_int_from_env("LAYER_HEIGHT"),
+    };
+}
+
+static struct layer_surface_t* layer_surface_hook_callback_impl(struct wl_surface* wl_surface) {
+    (void)wl_surface;
+    if (has_created_layer_surface && !get_bool_from_env("LAYER_ALL_SURFACES")) {
+        return NULL;
+    }
+    has_created_layer_surface = true;
+    struct layer_surface_t* layer_surface = malloc(sizeof(struct layer_surface_t));
+    *layer_surface = layer_surface_make();
+    layer_surface->get_preferred_size = get_preferred_size;
+    layer_surface_set_name_space(layer_surface, get_string_from_env("LAYER_NAMESPACE", "layer-shell-preload"));
+    layer_surface_set_anchor(layer_surface, get_edges_from_env("LAYER_ANCHOR"));
+    layer_surface_set_layer(layer_surface, get_layer_from_env("LAYER_LAYER"));
+    layer_surface_set_keyboard_mode(layer_surface, get_keyboard_interactivity_from_env("LAYER_KEYBOARD"));
+    if (get_bool_from_env("LAYER_EXCLUSIVE")) {
+        layer_surface_auto_exclusive_zone_enable(layer_surface);
+    }
+    return layer_surface;
+}
+
+__attribute__((constructor))
+static void setup(void) {
+    layer_surface_install_hook(layer_surface_hook_callback_impl);
+}
diff --git a/src/layer-surface.c b/src/layer-surface.c
index 912abc0..c5f9092 100644
--- a/src/layer-surface.c
+++ b/src/layer-surface.c
@@ -87,7 +87,7 @@ static void layer_surface_configure_xdg_surface(
         } {
             uint32_t* state = wl_array_add(&states, sizeof(uint32_t));
             assert(state);
-            *state = XDG_TOPLEVEL_STATE_MAXIMIZED;
+            *state = XDG_TOPLEVEL_STATE_FULLSCREEN;
         }
 
         LIBWAYLAND_SHIM_DISPATCH_CLIENT_EVENT(
diff --git a/src/meson.build b/src/meson.build
index cc92b7a..573ebc1 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -1,12 +1,15 @@
-srcs = files(
-    'gtk4-layer-shell.c',
-    'gtk4-session-lock.c',
+core_srcs = files(
     'stolen-from-libwayland.c',
     'libwayland-shim.c',
     'layer-surface.c',
     'lock-surface.c',
     'registry.c')
 
+gtk_srcs = files(
+    'gtk4-layer-shell.c',
+    'gtk4-session-lock.c',
+    )
+
 version_args = [
     '-DGTK_LAYER_SHELL_MAJOR=' + meson.project_version().split('.')[0],
     '-DGTK_LAYER_SHELL_MINOR=' + meson.project_version().split('.')[1],
@@ -14,7 +17,7 @@ version_args = [
 ]
 
 gtk_layer_shell_lib = library('gtk4-layer-shell',
-    srcs, client_protocol_srcs,
+    gtk_srcs, core_srcs, client_protocol_srcs,
     c_args: version_args,
     include_directories: [gtk_layer_shell_inc],
     dependencies: [gtk, wayland_client],
@@ -22,6 +25,12 @@ gtk_layer_shell_lib = library('gtk4-layer-shell',
     soversion: lib_so_version,
     install: true)
 
+layer_shell_preload_lib = library('layer-shell-preload',
+    files('layer-shell-preload.c'), core_srcs, client_protocol_srcs,
+    include_directories: [gtk_layer_shell_inc],
+    dependencies: [wayland_client],
+    install: true)
+
 pkg_config_name = 'gtk4-layer-shell-0'
 
 # GObject introspection file used to interface with other languages
@@ -29,7 +38,7 @@ if get_option('introspection')
     gir_layer = gnome.generate_gir(
         gtk_layer_shell_lib,
         dependencies: [gtk],
-        sources: srcs + files('../include/gtk4-layer-shell.h'),
+        sources: files('../include/gtk4-layer-shell.h') + gtk_srcs + core_srcs,
         namespace: 'Gtk4LayerShell',
         nsversion: '1.0',
         identifier_prefix: 'GtkLayerShell',
@@ -42,7 +51,7 @@ if get_option('introspection')
     gir_lock = gnome.generate_gir(
         gtk_layer_shell_lib,
         dependencies: [gtk],
-        sources: srcs + files('../include/gtk4-session-lock.h'),
+        sources: files('../include/gtk4-session-lock.h') + gtk_srcs + core_srcs,
         namespace: 'Gtk4SessionLock',
         nsversion: '1.0',
         identifier_prefix: 'GtkSessionLock',