ZZT is a DOS game designed with basic ANSI color w/ ASCII characters. The name was created so that it would be featured last in software collections. It features an adventure of puzzles and you must collect keys to unlock the ending of the game. Not only defined as a puzzle game, ZZT also requires quick reflexes as you'll be thrown into piles of enemies shooting projectiles at you, moving fast toward you and cornered with very little ammo. ZZT also has a huge library of user created levels that you can find online and play the adventure a whole new way. Custom games are developed with a custom language called ZZT-OOP. It's a great game for the brilliant of mind and fun for any age. Despite primitive graphics the game still has excellent replayability and offers a challenge unlike modern games.
The full version was released for free by MegaGames so disregard the "do not distribute" warning, it IS completely free now.