Review comments, see: #268

js/common/model/CurvePoint.ts

@@ -161,6 +161,7 @@ export default class CurvePoint {
    */
   public undo(): void {
 
+    // REVIEW: Why revert to initial state when we reach the undo limit? This seems strange to me https://github.com/phetsims/calculus-grapher/issues/287
     // Reverts the state of this CurvedPoint to its most-recently saved state (if available).
     // As a side effect, the state is popped off undoStack.
     const pointState = ( this.undoStack.length === 0 ) ? this.initialState : this.undoStack.pop()!;

js/common/model/DerivativeCurve.ts

@@ -92,6 +92,9 @@ export default class DerivativeCurve extends Curve {
       }
 
       if ( typeof leftSlope === 'number' && typeof rightSlope === 'number' ) {
+
+        // REVIEW: What does approximately equal mean? I see no analysis of how equal the slopes are before setting the
+        // REVIEW: derivative.
         // If both the left and right adjacent Points of the Point of the 'base' curve exist, the derivative is
         // the average of the slopes if they are approximately equal. Otherwise, the derivative doesn't exist.
         this.points[ index ].y = ( leftSlope + rightSlope ) / 2;

js/common/model/SecondDerivativeCurve.ts

@@ -46,6 +46,8 @@ export default class SecondDerivativeCurve extends Curve {
   }
 
   /**
+   * // REVIEW: This makes it sound like we're grabbing the derivative of the "base"/"original"
+   * // REVIEW: curve. But we're actually grabbing the derivative of the OG curve derivative.
    * Updates the y-values of the SecondDerivative to represent the derivative of the 'base' Curve.
    *
    * To update the second derivative, we (1) assume that the points are smooth,

js/common/model/TransformedCurve.ts

@@ -184,7 +184,7 @@ export default class TransformedCurve extends Curve {
     const deltaY = y - this.getClosestPointAt( x ).y;
 
     // Shift each of the CurvePoints by deltaY.
-    this.points.forEach( point => {point.y += deltaY;} );
+    this.points.forEach( point => { point.y += deltaY; } );
   }
 
   /**
@@ -560,6 +560,7 @@ export default class TransformedCurve extends Curve {
       // Point associated with the last drag event
       const nextToLastPoint = this.getClosestPointAt( antepenultimatePosition.x );
 
+      // REVIEW: should this be "lastPoint is in between closestPoint and nextToLastPoint"?
       // Checks that lastPoint is in between closestPoint and lastPoint
       if ( ( closestPoint.x - lastPoint.x ) * ( nextToLastPoint.x - lastPoint.x ) < 0 ) {