A solid entry, Everything that is there works well.
A bit of nitpicking:
Movement on KeyUp() is an unpleasant experience. You usually expect something to happen as soon as you press a key and not only after you release it. KeyDown == action like in every application/game.
Some walls had the same texture as the doors and that can be quiet irritating.
Something like an direction indicator that points to the exit would indeed help. It does not need to be active before you reach the terminal.