Dangerous Dave
Clyde, Dave's nemesis
After playing Dave for a bit you might wonder how the hell John got the ideas for the monsters, upside-down trees, the gun and the jetpack. Using a technique called page-flipping he created a smooth running game on the very slow Apple II. This meant that at any one time, one image is actively being displayed by the monitor, while the another background image is being drawn.
Another trick John Romero used was playing random game data through the Apple's speaker to create an explosion sound! Lot's of difficult routines for such a simple game.
