Up - go up, woah! Right - go forward, cool! Up + Right - go up and forward, I didn't know that! not Up - go down, duhh. not Right - go backwards, obviously. Don't worry, it isn't infinite.
No more cheesy introduction I made this in about 2 hours. Post if you could do it in the comments below :) Don't blame me if you smash your computer in frustration :P Thx :)