At the title screen, it says "Start game".
Don't press enter.
Instead, press Up, Down, Down, Left, Right, and Jump.
It will take you to the level select. There you'll see
two numbers and a letter. The first number represents
which zone. (e.g. Palmtree Panic, Collision Chaos).
The second number represents wehich act, like 1, 2 or 3.
The letter represents time: A=Present B=Past C=Good Future