diff --git a/Shared/Player.cs b/Shared/Player.cs
index 5124ffe..b083302 100644
--- a/Shared/Player.cs
+++ b/Shared/Player.cs
@@ -37,38 +37,29 @@ namespace SemiColinGames {
 
     public Point Position { get { return position; } }
 
-    private Rectangle Bbox(Point position) {
-      return new Rectangle(position.X - spriteWidth, position.Y - 7, spriteWidth * 2, 26);
-    }
-
-    private Aabb Box(Point position) {
-      return Box(position, 0);
-    }
+    public void Update(float modelTime, History<Input> input, Aabb[] collisionTargets) {
+      Aabb BoxOffset(Point position, int yOffset) {
+        return new Aabb(new Vector2(position.X, position.Y - 7 + spriteHeight + yOffset),
+            new Vector2(spriteWidth, spriteHeight));
+      }
 
-    private Aabb Box(Point position, int yOffset) {
-      return new Aabb(new Vector2(position.X, position.Y - 7 + spriteHeight + yOffset),
-          new Vector2(spriteWidth, spriteHeight));
-    }
+      Aabb Box(Point position) {
+        return BoxOffset(position, 0);
+      }
 
-    public void Update(float modelTime, History<Input> input, Rectangle[] collisionTargets) {
       Vector2 movement = HandleInput(modelTime, input);
 
-      // TODO: we shouldn't hardcode the tile sizes here.
-      Vector2 halfBoxSize = new Vector2(World.TileSize / 2, World.TileSize / 2);
       // Broad test: remove all collision targets nowhere near the player.
-      List<Rectangle> candidates = new List<Rectangle>();
+      var candidates = new List<Aabb>();
       // TODO: This is strictly larger than it needs to be. We could expand only in the actual
       // direction of movement.
       Aabb largeBox = new Aabb(
         new Vector2(position.X, position.Y - 7 + spriteHeight),  // current player position
         new Vector2(spriteWidth + Math.Abs(movement.X), spriteHeight + Math.Abs(movement.Y)));
-      for (int i = 0; i < collisionTargets.Length; i++) {
-        Rectangle rect = collisionTargets[i];
-        Aabb box = new Aabb(
-          new Vector2(rect.X + World.TileSize / 2, rect.Y + World.TileSize / 2), halfBoxSize);
+      foreach (var box in collisionTargets) {
         if (box.Intersect(largeBox) != null) {
           Debug.AddRect(box, Color.Green);
-          candidates.Add(rect);
+          candidates.Add(box);
         }
       }
 
@@ -80,9 +71,7 @@ namespace SemiColinGames {
           Point newPosition = new Point(position.X, position.Y + dy);
           Aabb player = Box(newPosition);
           bool reject = false;
-          foreach (var rect in candidates) {
-            Aabb box = new Aabb(
-              new Vector2(rect.X + World.TileSize / 2, rect.Y + World.TileSize / 2), halfBoxSize);
+          foreach (var box in candidates) {
             if (box.Intersect(player) != null) {
               reject = true;
               break;
@@ -96,9 +85,7 @@ namespace SemiColinGames {
           Point newPosition = new Point(position.X + dx, position.Y);
           Aabb player = Box(newPosition);
           bool reject = false;
-          foreach (var rect in candidates) {
-            Aabb box = new Aabb(
-              new Vector2(rect.X + World.TileSize / 2, rect.Y + World.TileSize / 2), halfBoxSize);
+          foreach (var box in candidates) {
             if (box.Intersect(player) != null) {
               reject = true;
               break;
@@ -111,24 +98,21 @@ namespace SemiColinGames {
       }
 
       bool standingOnGround = false;
-      Aabb groundIntersect = Box(position, 1);
-      foreach (var rect in candidates) {
-        Aabb box = new Aabb(
-          new Vector2(rect.X + World.TileSize / 2, rect.Y + World.TileSize / 2), halfBoxSize);
+      Aabb groundIntersect = BoxOffset(position, 1);
+      foreach (var box in candidates) {
         if (groundIntersect.Intersect(box) != null) {
           standingOnGround = true;
-          Debug.AddRect(rect, Color.Cyan);
-          // break;
+          break;
         }
       }
 
       if (standingOnGround) {
         jumps = 1;
         ySpeed = -0.0001f;
-        // Debug.AddRect(playerBbox, Color.Red);
+        Debug.AddRect(Box(position), Color.Cyan);
       } else {
         jumps = 0;
-        // Debug.AddRect(playerBbox, Color.Orange);
+        Debug.AddRect(Box(position), Color.Orange);
       }
 
       if (movement.X > 0) {
diff --git a/Shared/SneakGame.cs b/Shared/SneakGame.cs
index 4b61005..bee7f36 100644
--- a/Shared/SneakGame.cs
+++ b/Shared/SneakGame.cs
@@ -93,8 +93,7 @@ namespace SemiColinGames {
       if (!paused) {
         float modelTime = (float) gameTime.ElapsedGameTime.TotalSeconds;
         Clock.AddModelTime(modelTime);
-        Rectangle[] collisionTargets = world.CollisionTargets;
-        player.Update(modelTime, input, collisionTargets);
+        player.Update(modelTime, input, world.CollisionTargets);
         camera.Update(player.Position);
       }
 
diff --git a/Shared/World.cs b/Shared/World.cs
index e46c6ad..80b59ed 100644
--- a/Shared/World.cs
+++ b/Shared/World.cs
@@ -83,7 +83,7 @@ namespace SemiColinGames {
 
     public const int TileSize = 16;
     readonly Tile[] tiles;
-    readonly Rectangle[] collisionTargets;
+    readonly Aabb[] collisionTargets;
 
     public int Width { get; private set; }
     public int Height { get; private set; }
@@ -153,9 +153,13 @@ namespace SemiColinGames {
         }
       }
       tiles = tilesList.ToArray();
-      collisionTargets = new Rectangle[tiles.Length];
+      collisionTargets = new Aabb[tiles.Length];
+
+      Vector2 halfSize = new Vector2(TileSize / 2, TileSize / 2);
       for (int i = 0; i < tiles.Length; i++) {
-        collisionTargets[i] = tiles[i].Position;
+        Vector2 center = new Vector2(
+          tiles[i].Position.Left + halfSize.X, tiles[i].Position.Top + halfSize.Y);
+        collisionTargets[i] = new Aabb(center, halfSize);
       }
     }
 
@@ -165,7 +169,7 @@ namespace SemiColinGames {
       }
     }
 
-    public Rectangle[] CollisionTargets {
+    public Aabb[] CollisionTargets {
       get { return collisionTargets; }
     }
   }