Despite the border being 1px wide the whole 8x8 area is the collision zone which can give the impression that the game hasn't responded to input. This isn't how I would have designed it, but it is part of the original design from 1983 so I kept it. The control system feels a lot sharper on a joypad btw which is how i play it (Xbox One controller on Fuse, Switch controller on Retrogames The Spectrum). It's supposed to be fast to make it tricky :). Keyboard input is checked every single game loop, one game loop = one step.