Use the arrow keys to move around.
Scratch cat actually stays still and the background sprite moves. A ghosted hitbox sprite is used for collision detection instead of Scratch Cat himself so that he doesn't e.g. get his whiskers caught on stuff. Since he's staying still, the hitbox sprite doesn't need to follow him around, which is handy. When Scratch Cat hits a wall, we check to see if he can be "nudged" a bit and keep moving - this allows him to move along slopes without the player having to press e.g. up-left-up-left. The blocks to do this checking are set to "run without screen refresh" which lets them move the sprite, see if there's a collision, and if so move it back, with the player never seeing it happen.
