diff --git a/app/assets/javascripts/workers/worker_world.js b/app/assets/javascripts/workers/worker_world.js
index 04d63ea5d..dd1142eff 100644
--- a/app/assets/javascripts/workers/worker_world.js
+++ b/app/assets/javascripts/workers/worker_world.js
@@ -96,7 +96,9 @@ Aether.addGlobal('_', _);
 var serializedClasses = {
     "Thang": self.require('lib/world/thang'),
     "Vector": self.require('lib/world/vector'),
-    "Rectangle": self.require('lib/world/rectangle')
+    "Rectangle": self.require('lib/world/rectangle'),
+    "Ellipse": self.require('lib/world/ellipse'),
+    "LineSegment": self.require('lib/world/line_segment')
 };
 self.currentUserCodeMapCopy = "";
 self.currentDebugWorldFrame = 0;
diff --git a/app/lib/surface/Mark.coffee b/app/lib/surface/Mark.coffee
index 07f671e78..bce9d84be 100644
--- a/app/lib/surface/Mark.coffee
+++ b/app/lib/surface/Mark.coffee
@@ -181,12 +181,11 @@ module.exports = class Mark extends CocoClass
   buildDebug: ->
     @mark = new createjs.Shape()
     PX = 3
-    [w, h] = [Math.max(PX, @sprite.thang.width * Camera.PPM), Math.max(PX, @sprite.thang.height * Camera.PPM) * @camera.y2x]
+    [w, h] = [Math.max(PX, @sprite.thang.width * Camera.PPM), Math.max(PX, @sprite.thang.height * Camera.PPM) * @camera.y2x]  # TODO: doesn't work with rotation
     @mark.alpha = 0.5
     @mark.graphics.beginFill '#abcdef'
     if @sprite.thang.shape in ['ellipsoid', 'disc']
-      [w, h] = [Math.max(PX, w, h), Math.max(PX, w, h)]
-      @mark.graphics.drawCircle 0, 0, w / 2
+      @mark.graphics.drawEllipse -w / 2, -h / 2, w, h
     else
       @mark.graphics.drawRect -w / 2, -h / 2, w, h
     @mark.graphics.endFill()
@@ -259,7 +258,7 @@ module.exports = class Mark extends CocoClass
 
   updateRotation: ->
     if @name is 'debug' or (@name is 'shadow' and @sprite.thang?.shape in ['rectangle', 'box'])
-      @mark.rotation = @sprite.thang.rotation * 180 / Math.PI
+      @mark.rotation = -@sprite.thang.rotation * 180 / Math.PI
 
   updateScale: ->
     if @name is 'bounds' and ((@sprite.thang.width isnt @lastWidth or @sprite.thang.height isnt @lastHeight) or (@sprite.thang.drawsBoundsIndex isnt @drawsBoundsIndex))
diff --git a/app/lib/world/ellipse.coffee b/app/lib/world/ellipse.coffee
new file mode 100644
index 000000000..6aaf88057
--- /dev/null
+++ b/app/lib/world/ellipse.coffee
@@ -0,0 +1,174 @@
+Vector = require './vector'
+LineSegment = require './line_segment'
+Rectangle = require './rectangle'
+
+class Ellipse
+  @className: "Ellipse"
+
+  # TODO: add class methods for add, multiply, subtract, divide, rotate
+
+  isEllipse: true
+  apiProperties: ['x', 'y', 'width', 'height', 'rotation', 'distanceToPoint', 'distanceSquaredToPoint', 'distanceToRectangle', 'distanceSquaredToRectangle', 'distanceToEllipse', 'distanceSquaredToEllipse', 'distanceToShape', 'distanceSquaredToShape', 'containsPoint', 'intersectsLineSegment', 'intersectsRectangle', 'intersectsEllipse', 'getPos', 'containsPoint', 'copy']
+
+  constructor: (@x=0, @y=0, @width=0, @height=0, @rotation=0) ->
+
+  copy: ->
+    new Ellipse(@x, @y, @width, @height, @rotation)
+
+  getPos: ->
+    new Vector(@x, @y)
+
+  rectangle: ->
+    new Rectangle(@x, @y, @width, @height, @rotation)
+
+  axisAlignedBoundingBox: (rounded=true) ->
+    @rectangle().axisAlignedBoundingBox()
+
+  distanceToPoint: (p) ->
+    @rectangle().distanceToPoint p  # TODO: actually implement ellipse ellipse-point distance
+
+  distanceSquaredToPoint: (p) ->
+    # Doesn't handle rotation; just supposed to be faster than distanceToPoint.
+    @rectangle().distanceSquaredToPoint p  # TODO: actually implement ellipse-point distance
+
+  distanceToRectangle: (other) ->
+    Math.sqrt @distanceSquaredToRectangle other
+
+  distanceSquaredToRectangle: (other) ->
+    @rectangle().distanceSquaredToRectangle other  # TODO: actually implement ellipse-rectangle distance
+
+  distanceToEllipse: (ellipse) ->
+    Math.sqrt @distanceSquaredToEllipse ellipse
+
+  distanceSquaredToEllipse: (ellipse) ->
+    @rectangle().distanceSquaredToEllipse ellipse  # TODO: actually implement ellipse-ellipse distance
+
+  distanceToShape: (shape) ->
+    Math.sqrt @distanceSquaredToShape shape
+
+  distanceSquaredToShape: (shape) ->
+    if shape.isEllipse then @distanceSquaredToEllipse shape else @distanceSquaredToRectangle shape
+
+  containsPoint: (p, withRotation=true) ->
+    [a, b] = [@width / 2, @height / 2]
+    [h, k] = [@x, @y]
+    [x, y] = [p.x, p.y]
+    x2 = Math.pow(x, 2)
+    a2 = Math.pow(a, 2)
+    a4 = Math.pow(a, 4)
+    b2 = Math.pow(b, 2)
+    b4 = Math.pow(b, 4)
+    h2 = Math.pow(h, 2)
+    k2 = Math.pow(k, 2)
+    if withRotation and @rotation
+      sint = Math.sin(@rotation)
+      sin2t = Math.sin(2 * @rotation)
+      cost = Math.cos(@rotation)
+      cos2t = Math.cos(2 * @rotation)
+      numeratorLeft = (-a2 * h * sin2t) + (a2 * k * cos2t) + (a2 * k) + (a2 * x * sin2t)
+      numeratorMiddle = Math.SQRT2 * Math.sqrt((a4 * b2 * cos2t) + (a4 * b2) - (a2 * b4 * cos2t) + (a2 * b4) - (2 * a2 * b2 * h2) + (4 * a2 * b2 * h * x) - (2 * a2 * b2 * x2))
+      numeratorRight = (b2 * h * sin2t) - (b2 * k * cos2t) + (b2 * k) - (b2 * x * sin2t)
+      denominator = (a2 * cos2t) + a2 - (b2 * cos2t) + b2
+      solution1 = (numeratorLeft - numeratorMiddle + numeratorRight) / denominator
+      solution2 = (numeratorLeft + numeratorMiddle + numeratorRight) / denominator
+      if (not isNaN solution1) and (not isNaN solution2)
+        [bigSolution, littleSolution] = if solution1 > solution2 then [solution1, solution2] else [solution2, solution1]
+        if y > littleSolution and y < bigSolution
+          return true
+        else
+          return false
+      else
+        return false
+    else
+      numeratorLeft = a2 * k
+      numeratorRight = Math.sqrt((a4 * b2) - (a2 * b2 * h2) + (2 * a2 * b2 * h * x) - (a2 * b2 * x2))
+      denominator = a2
+      solution1 = (numeratorLeft + numeratorRight) / denominator
+      solution2 = (numeratorLeft - numeratorRight) / denominator
+      if (not isNaN solution1) and (not isNaN solution2)
+        [bigSolution, littleSolution] = if solution1 > solution2 then [solution1, solution2] else [solution2, solution1]
+        if y > littleSolution and y < bigSolution
+          return true
+        else
+          return false
+      else
+        return false
+    false
+
+  intersectsLineSegment: (p1, p2) ->
+    [px1, py1, px2, py2] = [p1.x, p1.y, p2.x, p2.y]
+    m = (py1 - py2) / (px1 - px2)
+    m2 = Math.pow(m, 2)
+    c = py1 - (m * px1)
+    c2 = Math.pow(c, 2)
+    [a, b] = [@width / 2, @height / 2]
+    [h, k] = [@x, @y]
+    a2 = Math.pow(a, 2)
+    a4 = Math.pow(a, 2)
+    b2 = Math.pow(b, 2)
+    b4 = Math.pow(b, 4)
+    h2 = Math.pow(h, 2)
+    k2 = Math.pow(k, 2)
+    sint = Math.sin(@rotation)
+    sin2t = Math.sin(2 * @rotation)
+    cost = Math.cos(@rotation)
+    cos2t = Math.cos(2 * @rotation)
+    if (not isNaN m) and m != Infinity and m != -Infinity
+      numeratorLeft = (-a2 * c * m * cos2t) - (a2 * c * m) + (a2 * c * sin2t) - (a2 * h * m * sin2t) - (a2 * h * cos2t) + (a2 * h) + (a2 * k * m * cos2t) + (a2 * k * m) - (a2 * k * sin2t)
+      numeratorMiddle = Math.SQRT2 * Math.sqrt((a4 * b2 * m2 * cos2t) + (a4 * b2 * m2) - (2 * a4 * b2 * m * sin2t) - (a4 * b2 * cos2t) + (a4 * b2) - (a2 * b4 * m2 * cos2t) + (a2 * b4 * m2) + (2 * a2 * b4 * m * sin2t) + (a2 * b4 * cos2t) + (a2 * b4) - (2 * a2 * b2 * c2) - (4 * a2 * b2 * c * h * m) + (4 * a2 * b2 * c * k) - (2 * a2 * b2 * h2 * m2) + (4 * a2 * b2 * h * k * m) - (2 * a2 * b2 * k2))
+      numeratorRight = (b2 * c * m * cos2t) - (b2 * c * m) - (b2 * c * sin2t) + (b2 * h * m * sin2t) + (b2 * h * cos2t) + (b2 * h) - (b2 * k * m * cos2t) + (b2 * k * m) + (b2 * k * sin2t)
+      denominator = (a2 * m2 * cos2t) + (a2 * m2) - (2 * a2 * m * sin2t) - (a2 * cos2t) + a2 - (b2 * m2 * cos2t) + (b2 * m2) + (2 * b2 * m * sin2t) + (b2 * cos2t) + b2
+      solution1 = (-numeratorLeft - numeratorMiddle + numeratorRight) / denominator
+      solution2 = (-numeratorLeft + numeratorMiddle + numeratorRight) / denominator
+      if (not isNaN solution1) and (not isNaN solution2)
+        [littleX, bigX] = if px1 < px2 then [px1, px2] else [px2, px1]
+        if (littleX <= solution1 and bigX >= solution1) or (littleX <= solution2 and bigX >= solution2)
+          return true
+      if (not isNaN solution1) or (not isNaN solution2)
+        solution = if not isNaN solution1 then solution1 else solution2
+        [littleX, bigX] = if px1 < px2 then [px1, px2] else [px2, px1]
+        if littleX <= solution and bigX >= solution
+          return true
+      else
+        return false
+    else
+      x = px1
+      x2 = Math.pow(x, 2)
+      numeratorLeft = (-a2 * h * sin2t) + (a2 * k * cos2t) + (a2 * k) + (a2 * x * sin2t)
+      numeratorMiddle = Math.SQRT2 * Math.sqrt((a4 * b2 * cos2t) + (a4 * b2) - (a2 * b4 * cos2t) + (a2 * b4) - (2 * a2 * b2 * h2) + (4 * a2 * b2 * h * x) - (2 * a2 * b2 * x2))
+      numeratorRight = (b2 * h * sin2t) - (b2 * k * cos2t) + (b2 * k) - (b2 * x * sin2t)
+      denominator = (a2 * cos2t) + a2 - (b2 * cos2t) + b2
+      solution1 = (numeratorLeft - numeratorMiddle + numeratorRight) / denominator
+      solution2 = (numeratorLeft + numeratorMiddle + numeratorRight) / denominator
+      if (not isNaN solution1) or (not isNaN solution2)
+        solution = if not isNaN solution1 then solution1 else solution2
+        [littleY, bigY] = if py1 < py2 then [py1, py2] else [py2, py1]
+        if littleY <= solution and bigY >= solution
+          return true
+      else
+        return false
+    false
+
+  intersectsRectangle: (rectangle) ->
+    rectangle.intersectsEllipse @
+
+  intersectsEllipse: (ellipse) ->
+    @rectangle().intersectsEllipse @  # TODO: actually implement ellipse-ellipse intersection
+    #return true if @containsPoint ellipse.getPos()
+
+  intersectsShape: (shape) ->
+    if shape.isEllipse then @intersectsEllipse shape else @intersectsRectangle shape
+
+  toString: ->
+    return "{x: #{@x.toFixed(0)}, y: #{@y.toFixed(0)}, w: #{@width.toFixed(0)}, h: #{@height.toFixed(0)}, rot: #{@rotation.toFixed(3)}}"
+
+  serialize: ->
+    {CN: @constructor.className, x: @x, y: @y, w: @width, h: @height, r: @rotation}
+
+  @deserialize: (o, world, classMap) ->
+    new Ellipse o.x, o.y, o.w, o.h, o.r
+
+  serializeForAether: -> @serialize()
+  @deserializeFromAether: (o) -> @deserialize o
+
+module.exports = Ellipse
diff --git a/app/lib/world/line_segment.coffee b/app/lib/world/line_segment.coffee
new file mode 100644
index 000000000..cf6de236a
--- /dev/null
+++ b/app/lib/world/line_segment.coffee
@@ -0,0 +1,80 @@
+class LineSegment
+  @className: "LineSegment"
+
+  constructor: (@a, @b) ->
+    @slope = (@a.y - @b.y) / (@a.x - @b.x)
+    @y0 = @a.y - (@slope * @a.x)
+    @left = if @a.x < @b.x then @a else @b
+    @right = if @a.x > @b.x then @a else @b
+    @bottom = if @a.y < @b.y then @a else @b
+    @top = if @a.y > @b.y then @a else @b
+
+  y: (x) ->
+    (@slope * x) + @y0
+
+  x: (y) ->
+    (y - @y0) / @slope
+
+  intersectsLineSegment: (lineSegment) ->
+    if lineSegment.slope is @slope
+      if lineSegment.y0 is @y0
+        if lineSegment.left.x is @left.x or lineSegment.left.x is @right.x or lineSegment.right.x is @right.x or lineSegment.right.x is @left.x
+          # segments are of the same line with shared start and/or end points
+          return true
+        else
+          [left, right] = if lineSegment.left.x < @left.x then [lineSegment, @] else [@, lineSegment]
+          if left.right.x > right.left.x
+            # segments are of the same line and one is contained within the other
+            return true
+    else if Math.abs(@slope) isnt Infinity and Math.abs(lineSegment.slope) isnt Infinity
+      x = (lineSegment.y0 - @y0) / (@slope - lineSegment.slope)
+      if x >= @left.x and x <= @right.x and x >= lineSegment.left.x and x <= lineSegment.right.x
+        return true
+    else if Math.abs(@slope) isnt Infinity or Math.abs(lineSegment.slope) isnt Infinity
+      [vertical, nonvertical] = if Math.abs(@slope) isnt Infinity then [lineSegment, @] else [@, lineSegment]
+      x = vertical.a.x
+      bottom = vertical.bottom.y
+      top = vertical.top.y
+      y = nonvertical.y(x)
+      left = nonvertical.left.x
+      right = nonvertical.right.x
+      if y >= bottom and y <= top and x >= left and x <= right
+        return true
+    false
+
+  pointOnLine: (point, segment=true) ->
+    if point.y is @y(point.x)
+      if segment
+        [littleY, bigY] = if @a.y < @b.y then [@a.y, @b.y] else [@b.y, @a.y]
+        if littleY <= point.y and bigY >= point.y
+          return true
+      else
+        return true
+    false
+
+  distanceSquaredToPoint: (point) ->
+    # http://stackoverflow.com/a/1501725/540620
+    return @a.distanceSquared point if @a.equals @b
+    res = Math.min point.distanceSquared(@a), point.distanceSquared(@b)
+    lineMagnitudeSquared = @a.distanceSquared @b
+    t = ((point.x - @a.x) * (@b.x - @a.x) + (point.y - @a.y) * (@b.y - @a.y)) / lineMagnitudeSquared
+    return @a.distanceSquared point if t < 0
+    return @b.distanceSquared point if t > 1
+    point.distanceSquared x: @a.x + t * (@b.x - @a.x), y: @a.y + t * (@b.y - @a.y)
+
+  distanceToPoint: (point) ->
+    Math.sqrt @distanceSquaredToPoint point
+
+  toString: ->
+    "lineSegment(a=#{@a}, b=#{@b}, slope=#{@slope}, y0=#{@y0}, left=#{@left}, right=#{@right}, bottom=#{@bottom}, top=#{@top})"
+
+  serialize: ->
+    {CN: @constructor.className, a: @a, b: @b}
+
+  @deserialize: (o, world, classMap) ->
+    new LineSegment o.a, o.b
+
+  serializeForAether: -> @serialize()
+  @deserializeFromAether: (o) -> @deserialize o
+
+module.exports = LineSegment
diff --git a/app/lib/world/rectangle.coffee b/app/lib/world/rectangle.coffee
index e3fec8d76..dadfaea25 100644
--- a/app/lib/world/rectangle.coffee
+++ b/app/lib/world/rectangle.coffee
@@ -1,14 +1,16 @@
 Vector = require './vector'
+LineSegment = require './line_segment'
 
 class Rectangle
   @className: 'Rectangle'
-  # Class methods for nondestructively operating
+  # Class methods for nondestructively operating - TODO: add rotate
   for name in ['add', 'subtract', 'multiply', 'divide']
     do (name) ->
       Rectangle[name] = (a, b) ->
         a.copy()[name](b)
 
-  apiProperties: ['x', 'y', 'width', 'height', 'rotation', 'getPos', 'vertices', 'touchesRect', 'touchesPoint', 'distanceToPoint', 'containsPoint', 'copy']
+  isRectangle: true
+  apiProperties: ['x', 'y', 'width', 'height', 'rotation', 'getPos', 'vertices', 'touchesRect', 'touchesPoint', 'distanceToPoint', 'distanceSquaredToPoint', 'distanceToRectangle', 'distanceSquaredToRectangle', 'distanceToEllipse', 'distanceSquaredToEllipse', 'distanceToShape', 'distanceSquaredToShape', 'containsPoint', 'copy', 'intersectsLineSegment', 'intersectsEllipse', 'intersectsRectangle', 'intersectsShape']
 
   constructor: (@x=0, @y=0, @width=0, @height=0, @rotation=0) ->
 
@@ -28,6 +30,14 @@ class Rectangle
       new Vector @x + (w2 * cos + h2 * sin), @y + (w2 * sin - h2 * cos)
     ]
 
+  lineSegments: ->
+    vertices = @vertices()
+    lineSegment0 = new LineSegment vertices[0], vertices[1]
+    lineSegment1 = new LineSegment vertices[1], vertices[2]
+    lineSegment2 = new LineSegment vertices[2], vertices[3]
+    lineSegment3 = new LineSegment vertices[3], vertices[0]
+    [lineSegment0, lineSegment1, lineSegment2, lineSegment3]
+
   touchesRect: (other) ->
     # Whether this rect shares part of any edge with other rect, for non-rotated, non-overlapping rectangles.
     # I think it says kitty-corner rects touch, but I don't think I want that.
@@ -62,25 +72,90 @@ class Rectangle
     box
 
   distanceToPoint: (p) ->
-    # Get p in rect's coordinate space, then operate in one quadrant
+    # Get p in rect's coordinate space, then operate in one quadrant.
     p = Vector.subtract(p, @getPos()).rotate(-@rotation)
     dx = Math.max(Math.abs(p.x) - @width / 2, 0)
     dy = Math.max(Math.abs(p.y) - @height / 2, 0)
     Math.sqrt dx * dx + dy * dy
 
   distanceSquaredToPoint: (p) ->
-    # Doesn't handle rotation; just supposed to be faster than distanceToPoint
+    # Doesn't handle rotation; just supposed to be faster than distanceToPoint.
     p = Vector.subtract(p, @getPos())
     dx = Math.max(Math.abs(p.x) - @width / 2, 0)
     dy = Math.max(Math.abs(p.y) - @height / 2, 0)
     dx * dx + dy * dy
 
+  distanceToRectangle: (other) ->
+    Math.sqrt @distanceSquaredToRectangle other
+
+  distanceSquaredToRectangle: (other) ->
+    return 0 if @intersectsRectangle other
+    [firstVertices, secondVertices] = [@vertices(), other.vertices()]
+    [firstEdges, secondEdges] = [@lineSegments(), other.lineSegments()]
+    ans = Infinity
+    for i in [0 ... 4]
+      for j in [0 ... firstEdges.length]
+        ans = Math.min ans, firstEdges[j].distanceSquaredToPoint(secondVertices[i])
+      for j in [0 ... secondEdges.length]
+        ans = Math.min ans, secondEdges[j].distanceSquaredToPoint(firstVertices[i])
+    ans
+
+  distanceToEllipse: (ellipse) ->
+    Math.sqrt @distanceSquaredToEllipse ellipse
+
+  distanceSquaredToEllipse: (ellipse) ->
+    @distanceSquaredToRectangle ellipse.rectangle()  # TODO: actually implement rectangle-ellipse distance
+
+  distanceToShape: (shape) ->
+    Math.sqrt @distanceSquaredToShape shape
+
+  distanceSquaredToShape: (shape) ->
+    if shape.isEllipse then @distanceSquaredToEllipse shape else @distanceSquaredToRectangle shape
+
   containsPoint: (p, withRotation=true) ->
     if withRotation and @rotation
       not @distanceToPoint(p)
     else
       @x - @width / 2 < p.x < @x + @width / 2 and @y - @height / 2 < p.y < @y + @height / 2
 
+  intersectsLineSegment: (p1, p2) ->
+    [px1, py1, px2, py2] = [p1.x, p1.y, p2.x, p2.y]
+    m1 = (py1 - py2) / (px1 - px2)
+    b1 = py1 - (m1 * px1)
+    vertices = @vertices()
+    lineSegments = [[vertices[0], vertices[1]], [vertices[1], vertices[2]], [vertices[2], vertices[3]], [vertices[3], vertices[0]]]
+    for lineSegment in lineSegments
+      [px1, py1, px2, py2] = [p1.x, p1.y, p2.x, p2.y]
+      m2 = (py1 - py2) / (px1 - px2)
+      b2 = py1 - (m * px1)
+      if m1 isnt m2
+        m = m1 - m2
+        b = b2 - b1
+        x = b / m
+        [littleX, bigX] = if px1 < px2 then [px1, px2] else [px2, px1]
+        if x >= littleX and x <= bigX
+          y = (m1 * x) + b1
+          [littleY, bigY] = if py1 < py2 then [py1, py2] else [py2, py1]
+          if littleY <= solution and bigY >= solution
+            return true
+    false
+
+  intersectsRectangle: (rectangle) ->
+    return true if @containsPoint rectangle.getPos()
+    for thisLineSegment in @lineSegments()
+      for thatLineSegment in rectangle.lineSegments()
+        if thisLineSegment.intersectsLineSegment(thatLineSegment)
+          return true
+    false
+
+  intersectsEllipse: (ellipse) ->
+    return true if @containsPoint ellipse.getPos()
+    return true for lineSegment in @lineSegments() when ellipse.intersectsLineSegment lineSegment.a, lineSegment.b
+    false
+
+  intersectsShape: (shape) ->
+    if shape.isEllipse then @intersectsEllipse shape else @intersectsRectangle shape
+
   subtract: (point) ->
     @x -= point.x
     @y -= point.y
@@ -102,10 +177,10 @@ class Rectangle
     @
 
   isEmpty: () ->
-    @width == 0 and @height == 0
+    @width is 0 and @height is 0
 
   invalid: () ->
-    return (@x == Infinity) || isNaN(@x) || @y == Infinity || isNaN(@y) || @width == Infinity || isNaN(@width) || @height == Infinity || isNaN(@height) || @rotation == Infinity || isNaN(@rotation)
+    return (@x is Infinity) || isNaN(@x) || @y is Infinity || isNaN(@y) || @width is Infinity || isNaN(@width) || @height is Infinity || isNaN(@height) || @rotation is Infinity || isNaN(@rotation)
 
   toString: ->
     return "{x: #{@x.toFixed(0)}, y: #{@y.toFixed(0)}, w: #{@width.toFixed(0)}, h: #{@height.toFixed(0)}, rot: #{@rotation.toFixed(3)}}"
diff --git a/app/lib/world/world.coffee b/app/lib/world/world.coffee
index eb496133b..f94a6d26a 100644
--- a/app/lib/world/world.coffee
+++ b/app/lib/world/world.coffee
@@ -1,5 +1,7 @@
 Vector = require './vector'
 Rectangle = require './rectangle'
+Ellipse = require './ellipse'
+LineSegment = require './line_segment'
 WorldFrame = require './world_frame'
 Thang = require './thang'
 ThangState = require './thang_state'
@@ -21,7 +23,7 @@ module.exports = class World
   apiProperties: ['age', 'dt']
   constructor: (@userCodeMap, classMap) ->
     # classMap is needed for deserializing Worlds, Thangs, and other classes
-    @classMap = classMap ? {Vector: Vector, Rectangle: Rectangle, Thang: Thang}
+    @classMap = classMap ? {Vector: Vector, Rectangle: Rectangle, Thang: Thang, Ellipse: Ellipse, LineSegment: LineSegment}
     Thang.resetThangIDs()
 
     @userCodeMap ?= {}
diff --git a/app/lib/world/world_utils.coffee b/app/lib/world/world_utils.coffee
index d6d5c1171..1398c409b 100644
--- a/app/lib/world/world_utils.coffee
+++ b/app/lib/world/world_utils.coffee
@@ -1,5 +1,7 @@
 Vector = require './vector'
 Rectangle = require './rectangle'
+Ellipse = require './ellipse'
+LineSegment = require './line_segment'
 Grid = require './Grid'
 
 module.exports.typedArraySupport = typedArraySupport = Float32Array?  # Not in IE until IE 10; we'll fall back to normal arrays
@@ -36,7 +38,7 @@ module.exports.clone = clone = (obj, skipThangs=false) ->
     flags += 'y' if obj.sticky?
     return new RegExp(obj.source, flags)
 
-  if (obj instanceof Vector) or (obj instanceof Rectangle)
+  if (obj instanceof Vector) or (obj instanceof Rectangle) or (obj instanceof Ellipse) or (obj instanceof LineSegment)
     return obj.copy()
 
   if skipThangs and obj.isThang
diff --git a/app/views/play/level/tome/spell_debug_view.coffee b/app/views/play/level/tome/spell_debug_view.coffee
index e69fadc98..54fceb2f5 100644
--- a/app/views/play/level/tome/spell_debug_view.coffee
+++ b/app/views/play/level/tome/spell_debug_view.coffee
@@ -6,6 +6,8 @@ serializedClasses =
   Thang: require 'lib/world/thang'
   Vector: require 'lib/world/vector'
   Rectangle: require 'lib/world/rectangle'
+  Ellipse: require 'lib/world/ellipse'
+  LineSegment: require 'lib/world/line_segment'
 
 module.exports = class DebugView extends View
   className: 'spell-debug-view'
diff --git a/test/app/lib/surface/camera.spec.coffee b/test/app/lib/surface/camera.spec.coffee
index f875a1135..9383ce89a 100644
--- a/test/app/lib/surface/camera.spec.coffee
+++ b/test/app/lib/surface/camera.spec.coffee
@@ -14,7 +14,7 @@ describe 'Camera (Surface point of view)', ->
 
     sup = cam.worldToSurface wop
     expect(sup.x).toBeCloseTo wop.x * Camera.PPM
-    expect(sup.y).toBeCloseTo cam.surfaceHeight - (wop.y + wop.z * cam.z2y) * cam.y2x * Camera.PPM
+    expect(sup.y).toBeCloseTo -(wop.y + wop.z * cam.z2y) * cam.y2x * Camera.PPM
 
     cap = cam.worldToCanvas wop
     expect(cap.x).toBeCloseTo (sup.x - cam.surfaceViewport.x) * cam.zoom
@@ -83,47 +83,48 @@ describe 'Camera (Surface point of view)', ->
   testAngles = [0, Math.PI / 4, null, Math.PI / 2]
   testFOVs = [Math.PI / 6, Math.PI / 3, Math.PI / 2, Math.PI]
 
-  xit 'handles lots of different cases correctly', ->
+  it 'handles lots of different cases correctly', ->
     for wop in testWops
       for size in testCanvasSizes
         for zoom in testZooms
           for target in testZoomTargets
             for angle in testAngles
               for fov in testFOVs
-                cam = new Camera size.width, size.height, size.width * Camera.MPP, size.height * Camera.MPP, testLayer, zoom, null, angle, fov
+                cam = new Camera {attr: (attr) -> if 'attr' is 'width' then size.width else size.height}, angle, fov
                 checkCameraPos cam, wop
                 cam.zoomTo target, zoom, 0
                 checkConversionsFromWorldPos wop, cam
                 checkCameraPos cam, wop
 
   it 'works at 90 degrees', ->
-    cam = new Camera {attr: (x) -> 100}, 100 * Camera.MPP, 100 * Camera.MPP
+    cam = new Camera {attr: (attr) -> 100}, Math.PI / 2
     expect(cam.x2y).toBeCloseTo 1
     expect(cam.x2z).toBeGreaterThan 9001
     expect(cam.z2y).toBeCloseTo 0
 
   it 'works at 0 degrees', ->
-    cam = new Camera {attr: (x) -> 100}, 100 * Camera.MPP, 100 * Camera.MPP
-    expect(cam.x2z).toBeGreaterThan 9001
-    expect(cam.x2y).toBeCloseTo 1
-    expect(cam.z2y).toBeCloseTo 0
+    cam = new Camera {attr: (attr) -> 100}, 0
+    expect(cam.x2y).toBeGreaterThan 9001
+    expect(cam.x2z).toBeCloseTo 1
+    expect(cam.z2y).toBeGreaterThan 9001
 
   it 'works at 45 degrees', ->
-    cam = new Camera {attr: (x) -> 100}, 100 * Camera.MPP, 100 * Camera.MPP
-    expect(cam.x2y).toBeCloseTo 1
-    expect(cam.x2z).toBeGreaterThan 9001
-    expect(cam.z2y).toBeCloseTo 0
+    cam = new Camera {attr: (attr) -> 100}, Math.PI / 4
+    expect(cam.x2y).toBeCloseTo Math.sqrt(2)
+    expect(cam.x2z).toBeCloseTo Math.sqrt(2)
+    expect(cam.z2y).toBeCloseTo 1
 
-  xit 'works at default angle of asin(0.75) ~= 48.9 degrees', ->
-    cam = new Camera {attr: (x) -> 100}, 100 * Camera.MPP, 100 * Camera.MPP
-    angle = 1 / Math.cos angle
+  it 'works at default angle of asin(0.75) ~= 48.9 degrees', ->
+    cam = new Camera {attr: (attr) -> 100}, null
+    angle = Math.asin(3 / 4)
     expect(cam.angle).toBeCloseTo angle
-    expect(cam.x2y).toBeCloseTo 1
-    expect(cam.x2z).toBeGreaterThan 9001
-    expect(cam.z2y).toBeCloseTo 0
+    expect(cam.x2y).toBeCloseTo 4 / 3
+    expect(cam.x2z).toBeCloseTo 1 / Math.cos angle
+    expect(cam.z2y).toBeCloseTo (4 / 3) * Math.cos angle
 
   xit 'works at 2x zoom, 90 degrees', ->
-    cam = new Camera {attr: (x) -> 100}, 100 * Camera.MPP, 100 * Camera.MPP
+    cam = new Camera {attr: (attr) -> 100}, Math.PI / 2
+    cam.zoomTo null, 2, 0
     checkCameraPos cam
     wop = x: 5, y: 2.5, z: 7
     cap = cam.worldToCanvas wop
@@ -143,7 +144,8 @@ describe 'Camera (Surface point of view)', ->
     expectPositionsEqual cap, {x: 0, y: 50}
 
   xit 'works at 2x zoom, 30 degrees', ->
-    cam = new Camera {attr: (x) -> 100}, 100 * Camera.MPP, 2 * 100 * Camera.MPP
+    cam = new Camera {attr: (attr) -> 100}, Math.PI / 6
+    cam.zoomTo null, 2, 0
     expect(cam.x2y).toBeCloseTo 1
     expect(cam.x2z).toBeGreaterThan 9001
     checkCameraPos cam
@@ -164,15 +166,18 @@ describe 'Camera (Surface point of view)', ->
     expectPositionsEqual cap, {x: 50, y: -100}
 
   it 'works at 2x zoom, 60 degree hFOV', ->
-    cam = new Camera {attr: (x) -> 100}, 100 * Camera.MPP, 100 * Camera.MPP
+    cam = new Camera {attr: (attr) -> 100}, null, Math.PI / 3
+    cam.zoomTo null, 2, 0
     checkCameraPos cam
 
-  xit 'works at 2x zoom, 60 degree hFOV, 40 degree hFOV', ->
-    cam = new Camera {attr: (x) -> x is 'height' ? 63.041494 : 100}, 100 * Camera.MPP, 63.041494 * Camera.MPP
+  it 'works at 2x zoom, 60 degree hFOV, 40 degree vFOV', ->
+    cam = new Camera {attr: (attr) -> if attr is 'height' then 63.041494 else 100}, null, Math.PI / 3
+    cam.zoomTo null, 2, 0
     checkCameraPos cam
 
-  xit 'works on a surface wider than it is tall, 30 degrees, default viewing upper left corner', ->
-    cam = new Camera {attr: (x) -> 100}, 200 * Camera.MPP, 2 * 50 * Camera.MPP
+  xit 'works at 2x zoom on a surface wider than it is tall, 30 degrees, default viewing upper left corner', ->
+    cam = new Camera {attr: (attr) -> 100}, Math.PI / 6  # 200 * Camera.MPP, 2 * 50 * Camera.MPP
+    cam.zoomTo null, 2, 0
     checkCameraPos cam
     expect(cam.zoom).toBeCloseTo 2
     wop = x: 5, y: 4, z: 6 * cam.y2z  # like x: 5, y: 10 out of world width: 20, height: 10
diff --git a/test/app/lib/world/ellipse.spec.coffee b/test/app/lib/world/ellipse.spec.coffee
new file mode 100644
index 000000000..bb71fdad5
--- /dev/null
+++ b/test/app/lib/world/ellipse.spec.coffee
@@ -0,0 +1,99 @@
+describe 'Ellipse', ->
+  Ellipse = require 'lib/world/ellipse'
+  Rectangle = require 'lib/world/rectangle'
+  Vector = require 'lib/world/vector'
+
+  #it 'contains its own center', ->
+  #  ellipse = new Ellipse 0, 0, 10, 10
+  #  expect(ellipse.containsPoint(new Vector 0, 0)).toBe true
+  #
+  #it 'contains a point when rotated', ->
+  #  ellipse = new Ellipse 0, -20, 40, 40, 3 * Math.PI / 4
+  #  p = new Vector 0, 2
+  #  expect(ellipse.containsPoint(p, true)).toBe true
+  #
+  #it 'contains more points properly', ->
+  #  # ellipse with y major axis, off-origin center, and 45 degree rotation
+  #  ellipse = new Ellipse 1, 2, 4, 6, Math.PI / 4
+  #  expect(ellipse.contains new Vector(1, 2)).toBe true
+  #  expect(ellipse.contains new Vector(-1, 3)).toBe true
+  #  expect(ellipse.contains new Vector(0, 4)).toBe true
+  #  expect(ellipse.contains new Vector(1, 4)).toBe true
+  #  expect(ellipse.contains new Vector(3, 0)).toBe true
+  #  expect(ellipse.contains new Vector(1, 0)).toBe true
+  #  expect(ellipse.contains new Vector(0, 1)).toBe true
+  #  expect(ellipse.contains new Vector(-1, 2)).toBe true
+  #  expect(ellipse.contains new Vector(2, 2)).toBe true
+  #  expect(ellipse.contains new Vector(0, 0)).toBe false
+  #  expect(ellipse.contains new Vector(0, 5)).toBe false
+  #  expect(ellipse.contains new Vector(3, 4)).toBe false
+  #  expect(ellipse.contains new Vector(4, 0)).toBe false
+  #  expect(ellipse.contains new Vector(2, -1)).toBe false
+  #  expect(ellipse.contains new Vector(0, -3)).toBe false
+  #  expect(ellipse.contains new Vector(-2, -2)).toBe false
+  #  expect(ellipse.contains new Vector(-2, 0)).toBe false
+  #  expect(ellipse.contains new Vector(-2, 4)).toBe false
+  #
+  #it 'correctly calculates distance to a faraway point', ->
+  #  ellipse = new Ellipse 100, 50, 20, 40
+  #  p = new Vector 200, 300
+  #  d = 10 * Math.sqrt(610)
+  #  expect(ellipse.distanceToPoint(p)).toBeCloseTo d
+  #  ellipse.rotation = Math.PI / 2
+  #  d = 80 * Math.sqrt(10)
+  #  expect(ellipse.distanceToPoint(p)).toBeCloseTo d
+  #
+  #it 'does not modify itself or target Vector when calculating distance', ->
+  #  ellipse = new Ellipse -100, -200, 1, 100
+  #  ellipse2 = ellipse.copy()
+  #  p = new Vector -100.25, -101
+  #  p2 = p.copy()
+  #  ellipse.distanceToPoint(p)
+  #  expect(p.x).toEqual p2.x
+  #  expect(p.y).toEqual p2.y
+  #  expect(ellipse.x).toEqual ellipse2.x
+  #  expect(ellipse.y).toEqual ellipse2.y
+  #  expect(ellipse.width).toEqual ellipse2.width
+  #  expect(ellipse.height).toEqual ellipse2.height
+  #  expect(ellipse.rotation).toEqual ellipse2.rotation
+  #
+  #it 'correctly calculates distance to contained point', ->
+  #  ellipse = new Ellipse -100, -200, 1, 100
+  #  ellipse2 = ellipse.copy()
+  #  p = new Vector -100.25, -160
+  #  p2 = p.copy()
+  #  expect(ellipse.distanceToPoint(p)).toBe 0
+  #  ellipse.rotation = 0.00000001 * Math.PI
+  #  expect(ellipse.distanceToPoint(p)).toBe 0
+  #
+  #it 'AABB works when not rotated', ->
+  #  ellipse = new Ellipse 10, 20, 30, 40
+  #  rect = new Rectangle 10, 20, 30, 40
+  #  aabb1 = ellipse.axisAlignedBoundingBox()
+  #  aabb2 = ellipse.axisAlignedBoundingBox()
+  #  for prop in ['x', 'y', 'width', 'height']
+  #    expect(aabb1[prop]).toBe aabb2[prop]
+  #
+  #it 'AABB works when rotated', ->
+  #  ellipse = new Ellipse 10, 20, 30, 40, Math.PI / 3
+  #  rect = new Rectangle 10, 20, 30, 40, Math.PI / 3
+  #  aabb1 = ellipse.axisAlignedBoundingBox()
+  #  aabb2 = ellipse.axisAlignedBoundingBox()
+  #  for prop in ['x', 'y', 'width', 'height']
+  #    expect(aabb1[prop]).toBe aabb2[prop]
+  #
+  #it 'calculates ellipse intersections properly', ->
+  #  # ellipse with y major axis, off-origin center, and 45 degree rotation
+  #  ellipse = new Ellipse 1, 2, 4, 6, Math.PI / 4
+  #  expect(ellipse.intersectsShape new Rectangle(0, 0, 2, 2, 0)).toBe true
+  #  expect(ellipse.intersectsShape new Rectangle(0, -1, 2, 3, 0)).toBe true
+  #  expect(ellipse.intersectsShape new Rectangle(-1, -0.5, 2 * Math.SQRT2, 2 * Math.SQRT2, Math.PI / 4)).toBe true
+  #  expect(ellipse.intersectsShape new Rectangle(-1, -0.5, 2 * Math.SQRT2, 2 * Math.SQRT2, 0)).toBe true
+  #  expect(ellipse.intersectsShape new Rectangle(-1, -1, 2 * Math.SQRT2, 2 * Math.SQRT2, 0)).toBe true
+  #  expect(ellipse.intersectsShape new Rectangle(-1, -1, 2 * Math.SQRT2, 2 * Math.SQRT2, Math.PI / 4)).toBe false
+  #  expect(ellipse.intersectsShape new Rectangle(-2, -2, 2, 2, 0)).toBe false
+  #  expect(ellipse.intersectsShape new Rectangle(-Math.SQRT2 / 2, -Math.SQRT2 / 2, Math.SQRT2, Math.SQRT2, 0)).toBe false
+  #  expect(ellipse.intersectsShape new Rectangle(-Math.SQRT2 / 2, -Math.SQRT2 / 2, Math.SQRT2, Math.SQRT2, Math.PI / 4)).toBe false
+  #  expect(ellipse.intersectsShape new Rectangle(-2, 0, 2, 2, 0)).toBe false
+  #  expect(ellipse.intersectsShape new Rectangle(0, -2, 2, 2, 0)).toBe false
+  #  expect(ellipse.intersectsShape new Rectangle(1, 2, 1, 1, 0)).toBe true
diff --git a/test/app/lib/world/line_segment.spec.coffee b/test/app/lib/world/line_segment.spec.coffee
new file mode 100644
index 000000000..d3b6ca939
--- /dev/null
+++ b/test/app/lib/world/line_segment.spec.coffee
@@ -0,0 +1,51 @@
+describe 'LineSegment', ->
+  LineSegment = require 'lib/world/line_segment'
+  Vector = require 'lib/world/vector'
+
+  v00 = new Vector(0, 0)
+  v11 = new Vector(1, 1)
+  v22 = new Vector(2, 2)
+  v34 = new Vector(3, 4)
+  v04 = new Vector(0, 4)
+  v30 = new Vector(3, 0)
+  vneg = new Vector(-1, -1)
+
+  it 'intersects itself', ->
+    lineSegment = new LineSegment v00, v34
+    expect(lineSegment.intersectsLineSegment lineSegment).toBe true
+
+  it 'intersects other segments properly', ->
+    l1 = new LineSegment v00, v34
+    l2 = new LineSegment v04, v30
+    l3 = new LineSegment v00, v11
+    expect(l1.intersectsLineSegment l2).toBe true
+    expect(l2.intersectsLineSegment l1).toBe true
+    expect(l1.intersectsLineSegment l3).toBe true
+    expect(l3.intersectsLineSegment l1).toBe true
+    expect(l2.intersectsLineSegment l3).toBe false
+    expect(l3.intersectsLineSegment l2).toBe false
+
+  it 'can tell when a point is on a line or segment', ->
+    lineSegment = new LineSegment v00, v11
+    expect(lineSegment.pointOnLine v22, false).toBe true
+    #expect(lineSegment.pointOnLine v22, true).toBe false
+    #expect(lineSegment.pointOnLine v00, false).toBe true
+    #expect(lineSegment.pointOnLine v00, true).toBe true
+    #expect(lineSegment.pointOnLine v11, true).toBe true
+    #expect(lineSegment.pointOnLine v11, false).toBe true
+    #expect(lineSegment.pointOnLine v34, false).toBe false
+    #expect(lineSegment.pointOnLine v34, true).toBe false
+
+  it 'correctly calculates distance to points', ->
+    lineSegment = new LineSegment v00, v11
+    expect(lineSegment.distanceToPoint v00).toBe 0
+    expect(lineSegment.distanceToPoint v11).toBe 0
+    expect(lineSegment.distanceToPoint v22).toBeCloseTo Math.SQRT2
+    expect(lineSegment.distanceToPoint v34).toBeCloseTo Math.sqrt(2 * 2 + 3 * 3)
+    expect(lineSegment.distanceToPoint v04).toBeCloseTo Math.sqrt(1 * 1 + 3 * 3)
+    expect(lineSegment.distanceToPoint v30).toBeCloseTo Math.sqrt(2 * 2 + 1 * 1)
+    expect(lineSegment.distanceToPoint vneg).toBeCloseTo Math.SQRT2
+
+    nullSegment = new LineSegment v11, v11
+    expect(lineSegment.distanceToPoint v11).toBe 0
+    expect(lineSegment.distanceToPoint v22).toBeCloseTo Math.SQRT2
diff --git a/test/app/lib/world/rectangle.spec.coffee b/test/app/lib/world/rectangle.spec.coffee
index 76b13e0d3..937e388c5 100644
--- a/test/app/lib/world/rectangle.spec.coffee
+++ b/test/app/lib/world/rectangle.spec.coffee
@@ -1,6 +1,7 @@
 describe 'Rectangle', ->
   Rectangle = require 'lib/world/rectangle'
   Vector = require 'lib/world/vector'
+  Ellipse = require 'lib/world/ellipse'
 
   it 'contains its own center', ->
     rect = new Rectangle 0, 0, 10, 10
@@ -43,6 +44,13 @@ describe 'Rectangle', ->
     rect.rotation = 0.00000001 * Math.PI
     expect(rect.distanceToPoint(p)).toBe 0
 
+  it 'correctly calculates distance to other rectangles', ->
+    expect(new Rectangle(0, 0, 4, 4, Math.PI / 4).distanceToRectangle(new Rectangle(4, -4, 2, 2, 0))).toBeCloseTo 2.2426
+    expect(new Rectangle(0, 0, 3, 3, 0).distanceToRectangle(new Rectangle(0, 0, 2, 2, 0))).toBe 0
+    expect(new Rectangle(0, 0, 3, 3, 0).distanceToRectangle(new Rectangle(0, 0, 2.5, 2.5, Math.PI / 4))).toBe 0
+    expect(new Rectangle(0, 0, 4, 4, 0).distanceToRectangle(new Rectangle(4, 2, 2, 2, 0))).toBe 1
+    expect(new Rectangle(0, 0, 4, 4, 0).distanceToRectangle(new Rectangle(4, 2, 2, 2, Math.PI / 4))).toBeCloseTo 2 - Math.SQRT2
+
   it 'has predictable vertices', ->
     rect = new Rectangle 50, 50, 100, 100
     v = rect.vertices()
@@ -79,3 +87,22 @@ describe 'Rectangle', ->
     aabb = rect.axisAlignedBoundingBox()
     for prop in ['x', 'y', 'width', 'height']
       expect(rect[prop]).toBe aabb[prop]
+
+  it 'calculates rectangle intersections properly', ->
+    rect = new Rectangle 1, 1, 2, 2, 0
+    expect(rect.intersectsShape new Rectangle(3, 1, 2, 2, 0)).toBe true
+    expect(rect.intersectsShape new Rectangle(3, 3, 2, 2, 0)).toBe true
+    expect(rect.intersectsShape new Rectangle(1, 1, 2, 2, 0)).toBe true
+    expect(rect.intersectsShape new Rectangle(1, 1, Math.SQRT1_2, Math.SQRT1_2, Math.PI / 4)).toBe true
+    expect(rect.intersectsShape new Rectangle(4, 1, 2, 2, 0)).toBe false
+    expect(rect.intersectsShape new Rectangle(3, 4, 2, 2, 0)).toBe false
+    expect(rect.intersectsShape new Rectangle(1, 4, 2 * Math.SQRT1_2, 2 * Math.SQRT1_2, Math.PI / 4)).toBe false
+    expect(rect.intersectsShape new Rectangle(3, 1, 2, 2, Math.PI / 4)).toBe true
+    expect(rect.intersectsShape new Rectangle(1, 2, 2 * Math.SQRT2, 2 * Math.SQRT2, Math.PI / 4)).toBe true
+
+  it 'calculates ellipse intersections properly', ->
+    rect = new Rectangle 1, 1, 2, 2, 0
+    expect(rect.intersectsShape new Ellipse(1, 1, Math.SQRT1_2, Math.SQRT1_2, Math.PI / 4)).toBe true
+    expect(rect.intersectsShape new Ellipse(4, 1, 2, 2, 0)).toBe false
+    expect(rect.intersectsShape new Ellipse(3, 4, 2, 2, 0)).toBe false
+    expect(rect.intersectsShape new Ellipse(1, 4, 2 * Math.SQRT1_2, 2 * Math.SQRT1_2, Math.PI / 4)).toBe false