In 20th Century Frog, you play as a frog hopping around the screen to eat bugs and avoid deadly obstacles. Every alphanumeric key of the keyboard is used to control the movement of the frog, where the key's position relative to the space bar determines the direction and distance of the jump. Each hop consumes points, and each bug you eat replenishes them. If your points dip too far into the negative, the frog will perish. Eating ladybugs grants a "gimmick", a power up that can be used to counter a particular obstacle.