diff --git a/Shared/Player.cs b/Shared/Player.cs
index b083302..93931d8 100644
--- a/Shared/Player.cs
+++ b/Shared/Player.cs
@@ -17,13 +17,18 @@ namespace SemiColinGames {
     private const int jumpSpeed = -600;
     private const int gravity = 2400;
 
+    // Details of the sprite image.
     private const int spriteSize = 48;
-    // TODO: rename to spriteHalfWidth / spriteHalfHeight.
-    private const int spriteWidth = 7;
-    private const int spriteHeight = 13;
+    private const int spriteCenterYOffset = 5;
     private readonly Texture2D texture;
 
-    private Point position = new Point(64, 16 * 10);
+    // Details of the actual Player model.
+    
+    // Position is tracked at the Player's center. The Player's bounding box is a rectangle
+    // centered at that point and extending out by halfSize.X and halfSize.Y.
+    private Point position = new Point(64, 16 * 13);
+    private Vector2 halfSize = new Vector2(7, 14);
+
     private int jumps = 0;
     private Facing facing = Facing.Right;
     private Pose pose = Pose.Jumping;
@@ -39,8 +44,7 @@ namespace SemiColinGames {
 
     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));
+        return new Aabb(new Vector2(position.X, position.Y + yOffset), halfSize);
       }
 
       Aabb Box(Point position) {
@@ -54,8 +58,8 @@ namespace SemiColinGames {
       // 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)));
+        new Vector2(position.X, position.Y),  // current player position
+        new Vector2(halfSize.X + Math.Abs(movement.X), halfSize.Y + Math.Abs(movement.Y)));
       foreach (var box in collisionTargets) {
         if (box.Intersect(largeBox) != null) {
           Debug.AddRect(box, Color.Green);
@@ -195,7 +199,7 @@ namespace SemiColinGames {
     public void Draw(SpriteBatch spriteBatch, Camera camera) {
       int index = SpriteIndex(pose);
       Rectangle textureSource = new Rectangle(index * spriteSize, 0, spriteSize, spriteSize);
-      Vector2 spriteCenter = new Vector2(spriteSize / 2, spriteSize / 2);
+      Vector2 spriteCenter = new Vector2(spriteSize / 2, spriteSize / 2 + spriteCenterYOffset);
       SpriteEffects effect = facing == Facing.Right ?
         SpriteEffects.FlipHorizontally : SpriteEffects.None;
       Vector2 drawPos = new Vector2(position.X - camera.Left, position.Y);