diff --git a/Jumpy.Shared/Debug.cs b/Jumpy.Shared/Debug.cs
new file mode 100644
index 0000000..79b4401
--- /dev/null
+++ b/Jumpy.Shared/Debug.cs
@@ -0,0 +1,58 @@
+using Microsoft.Xna.Framework;
+using Microsoft.Xna.Framework.Graphics;
+using System.Collections.Generic;
+
+namespace Jumpy {
+  // TODO: add a WriteLine sort of functionality.
+  static class Debug {
+    struct DebugRect {
+      public Rectangle rect;
+      public Color color;
+
+      public DebugRect(Rectangle rect, Color color) {
+        this.rect = rect;
+        this.color = color;
+      }
+    }
+
+    public static bool Enabled;
+    static List<DebugRect> rects = new List<DebugRect>();
+    static Texture2D whiteTexture;
+
+
+    public static void Initialize(GraphicsDevice graphics) {
+      whiteTexture = new Texture2D(graphics, 1, 1);
+      whiteTexture.SetData(new Color[] { Color.White });
+    }
+    
+    public static void Clear() {
+      rects.Clear();
+    }
+
+    public static void AddRect(Rectangle rect, Color color) {
+      rects.Add(new DebugRect(rect, color));
+    }
+
+    public static void Draw(SpriteBatch spriteBatch) {
+      if (!Enabled) {
+        return;
+      }
+      foreach (var debugRect in rects) {
+        var rect = debugRect.rect;
+        var color = debugRect.color;
+        // top side
+        spriteBatch.Draw(
+          whiteTexture, new Rectangle(rect.Left, rect.Top, rect.Width, 1), color);
+        // bottom side
+        spriteBatch.Draw(
+          whiteTexture, new Rectangle(rect.Left, rect.Bottom - 1, rect.Width, 1), color);
+        // left side
+        spriteBatch.Draw(
+          whiteTexture, new Rectangle(rect.Left, rect.Top, 1, rect.Height), color);
+        // right side
+        spriteBatch.Draw(
+          whiteTexture, new Rectangle(rect.Right - 1, rect.Top, 1, rect.Height), color);
+      }
+    }
+  }
+}
diff --git a/Jumpy.Shared/Jumpy.Shared.projitems b/Jumpy.Shared/Jumpy.Shared.projitems
index 6af77e9..b84ae77 100644
--- a/Jumpy.Shared/Jumpy.Shared.projitems
+++ b/Jumpy.Shared/Jumpy.Shared.projitems
@@ -10,6 +10,7 @@
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="$(MSBuildThisFileDirectory)Camera.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Debug.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)FpsCounter.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)History.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)IDisplay.cs" />
diff --git a/Jumpy.Shared/JumpyGame.cs b/Jumpy.Shared/JumpyGame.cs
index 36d3474..8ddf9ae 100644
--- a/Jumpy.Shared/JumpyGame.cs
+++ b/Jumpy.Shared/JumpyGame.cs
@@ -26,7 +26,6 @@ namespace Jumpy {
     FpsCounter fpsCounter = new FpsCounter();
     Texture2D grasslandBg1;
     Texture2D grasslandBg2;
-    Texture2D whiteTexture;
 
     Player player;
     World world;
@@ -42,7 +41,9 @@ namespace Jumpy {
       display = (IDisplay) Services.GetService(typeof(IDisplay));
       display.Initialize(Window, graphics);
       display.SetFullScreen(fullScreen);
-            
+
+      Debug.Initialize(GraphicsDevice);
+
       for (int i = 0; i < renderTargets.Length; i++) {
         renderTargets[i] = new RenderTarget2D(
           GraphicsDevice, Camera.Width, Camera.Height, false /* mipmap */,
@@ -63,8 +64,6 @@ namespace Jumpy {
       // TODO: move backgrounds into World.
       grasslandBg1 = Content.Load<Texture2D>("grassland_bg1");
       grasslandBg2 = Content.Load<Texture2D>("grassland_bg2");
-      whiteTexture = new Texture2D(GraphicsDevice, 1, 1);
-      whiteTexture.SetData(new Color[] { Color.White });
     }
 
     // Called once per game. Unloads all game content.
@@ -74,6 +73,8 @@ namespace Jumpy {
 
     // Updates the game world.
     protected override void Update(GameTime gameTime) {
+      Debug.Clear();
+
       gamePad.Add(GamePad.GetState(PlayerIndex.One));
       keyboard.Add(Keyboard.GetState());
 
@@ -87,27 +88,17 @@ namespace Jumpy {
         display.SetFullScreen(fullScreen);
       }
 
+      if (gamePad[0].IsButtonDown(Buttons.LeftShoulder) &&
+          gamePad[1].IsButtonUp(Buttons.LeftShoulder)) {
+        Debug.Enabled = !Debug.Enabled;
+      }
+
       List<Rectangle> collisionTargets = world.CollisionTargets();
-      player.Update(gameTime, gamePad);
+      player.Update(gameTime, gamePad, collisionTargets);
 
       base.Update(gameTime);
     }
 
-    private void DrawRect(SpriteBatch spriteBatch, Rectangle rect, Color color) {
-      // top side
-      spriteBatch.Draw(
-        whiteTexture, new Rectangle(rect.Left, rect.Top, rect.Width, 1), color);
-      // bottom side
-      spriteBatch.Draw(
-        whiteTexture, new Rectangle(rect.Left, rect.Bottom - 1, rect.Width, 1), color);
-      // left side
-      spriteBatch.Draw(
-        whiteTexture, new Rectangle(rect.Left, rect.Top, 1, rect.Height), color);
-      // right side
-      spriteBatch.Draw(
-        whiteTexture, new Rectangle(rect.Right - 1, rect.Top, 1, rect.Height), color);
-    }
-
     // Called when the game should draw itself.
     protected override void Draw(GameTime gameTime) {
       // We need to update the FPS counter in Draw() since Update() might get called more
@@ -135,9 +126,7 @@ namespace Jumpy {
       world.Draw(spriteBatch);
 
       // Draw debug rects.
-      foreach (var rect in world.CollisionTargets()) {
-        DrawRect(spriteBatch, rect, Color.Yellow);
-      }
+      Debug.Draw(spriteBatch);
 
       // Aaaaand we're done.
       spriteBatch.End();
diff --git a/Jumpy.Shared/Player.cs b/Jumpy.Shared/Player.cs
index 55ccec0..383e605 100644
--- a/Jumpy.Shared/Player.cs
+++ b/Jumpy.Shared/Player.cs
@@ -2,6 +2,7 @@
 using Microsoft.Xna.Framework.Graphics;
 using Microsoft.Xna.Framework.Input;
 using System;
+using System.Collections.Generic;
 
 namespace Jumpy {
   class Player {
@@ -32,7 +33,23 @@ namespace Jumpy {
 
     // TODO: refactor input to have a virtual "which directions & buttons were being pressed"
     // instead of complicated if-statements in this function.
-    public void Update(GameTime time, History<GamePadState> gamePad) {
+    public void Update(
+        GameTime time, History<GamePadState> gamePad, List<Rectangle> collisionTargets) {
+      UpdateFromGamePad(time, gamePad);
+
+      Rectangle playerBbox =
+        new Rectangle(position.X - spriteWidth, position.Y - 9, spriteWidth * 2, 28);
+      Debug.AddRect(playerBbox, Color.Red);
+      foreach (var rect in collisionTargets) {
+        if (playerBbox.Intersects(rect)) {
+          Debug.AddRect(rect, Color.Yellow);
+        } else {
+          Debug.AddRect(rect, Color.Green);
+        }
+      }
+    }
+
+    void UpdateFromGamePad(GameTime time, History<GamePadState> gamePad) {
       if (gamePad[0].IsButtonDown(Buttons.A) && airState == AirState.Ground) {
         pose = Pose.Jumping;
         airState = AirState.Jumping;