I want to make a game similar to the old "Caverns of Mars" (from my childhood) where I can either randomly generate or paint in Photoshop some cavern walls and navigate a spaceship through them. If the object (rocket/spaceship) touches the edge (i.e. the green border in the example) the object blows up. I may want to build some really graphic mazes and whatnot with Photoshop, so I think a specific target color might be good -- but I have no idea how to do something like that. (Or if it's possible). Thanks in advance.