Fix bug in shape definition

Previously, `points` would be reused and (for example)
rotated multiple times, rather than once by the desired
angle, which resulted in nonsensical variant order.

Now, variants with indices 0 to 3 correctly correspond
to rotations of 0, 90, 180 and 270 degrees.

world/layers/matter.gd

@@ -5,6 +5,7 @@ static var REGISTRY := Registry.new()
 static var NONE    := Matter.new("none")
 static var PLASTIC := Matter.new("plastic")
 
+## Default matter to return when chunk or layer is not found.
 static var DEFAULT := NONE
 
 var id   : int

world/layers/shape.gd

@@ -9,6 +9,7 @@ static func lookup(id: int) -> Shape:
 static var EMPTY : Shape
 static var FULL  : Shape
 
+## Default shape to return when chunk or layer is not found.
 static var DEFAULT : Shape
 
 var id     : int
@@ -34,6 +35,8 @@ func _init(base: Base, mirror: bool, angle: int, shape: Shape2D, points: PackedV
 		uvs.append((Vector2.ONE / 2) + point)
 
 
+## Represents a base shape, before it has been rotated and mirrored
+## (if applicable) to create a number of variants based on that shape.
 class Base:
 	static var EMPTY          := Base.new("empty")
 	static var FULL           := Base.new("full"          , _rect())
@@ -60,28 +63,25 @@ class Base:
 				shape = _rotate(shape) # rotate by 90 degrees (swap x and y components)
 				variants.append(Shape.new(self, false, 0, shape, _points(shape)))
 		elif shape is Array:
-			# Convert points (pairs of ints) in array to convex shape.
+			# Convert points (pairs of `int`s) in `Array` to convex shape.
 			var factor := float(shape.max())
-			var points := PackedVector2Array()
+			var points_orig := PackedVector2Array() # untransformed points
 			for i in range(0, shape.size(), 2):
 				var point := Vector2(shape[i] / factor, shape[i + 1] / factor)
-				points.append(point - (Vector2.ONE / 2)) # ensure shape is centered
+				points_orig.append(point - (Vector2.ONE / 2)) # ensure shape is centered
 
 			# Add variations of the shape (rotated, mirrored), including the standard shape.
 			for mirror in [ false, true ] if mirrored else [ false ]:
-				if mirror:
-					# Mirror (flip) points along the X axis.
-					points = points.duplicate()
-					for i in points.size():
-						points[i] = points[i] * Transform2D.FLIP_X
-
 				for angle in [ 0, 90, 180, 270 ] if rotated else [ 0 ]:
-					if angle != 0:
+					var points := points_orig.duplicate() # transformed points
-						# Rotate points around the center.
+					# Technically we could skip `duplicate()` if not mirrored and not rotated, but eh.
+
+					if mirror: # Mirror (flip) points along the X axis.
+						for i in points.size(): points[i] *= Transform2D.FLIP_X
+
+					if angle != 0: # Rotate points around the center.
 						var transform := Transform2D(deg_to_rad(angle), Vector2.ZERO)
-						points = points.duplicate()
+						for i in points.size(): points[i] *= transform
-						for i in points.size():
-							points[i] = points[i] * transform
 
 					var shape_points: PackedVector2Array
 					for point in points: shape_points.append(point * Block.SIZE)