These 3D maze things were always cool. RATRUN places you in a randomly-generated maze, where you are the "rat" with the goal of finding your way to the cheese. Your position in the maze is drawn from a first-person perspective, and you're given a little number in the upper left corner that indicates the as-the-crow-flies distance to your goal. This number can be deceptive, though—you may find yourself one tile away from the cheese but on the wrong side of a wall in a dead-end passage. The screen refresh will feel a bit slow to modern players but it's actually not too bad considering that the entire game is written in BASIC.