In Slime, the player controls a small warship, which moves horizontally on the bottom of the screen. It is surrounded by an Absorber on either side of the bottom of the screen. Alien vessels will drop slimes from the heavens, and the player must shoot out wedge-shaped barricades, with the hope of directing slimes into the Absorbers, or at least preventing them from reaching the sea. While doing this, alien spaceships will intermittently plug your Absorbers, or shoot down your wedges. As slimes reach the ocean, the sea level will rise, and when the seas reach the top of the screen, it's game over.
In this game, you guide a marker which must draw rectangles and other weird objects in order to claim your territory, and you can either draw these rectangles fast or slow. Drawing the rectangles using the "slow" method awards you the most points. Once a rectangle has been made, it will be colored in to show that you have claimed your territory. While drawing the rectangles, you need to watch out for Qix (pronounced "kicks"), a series of colored lines that crawl the screen. In addition to Qix, you also need to avoid the Sparks who travel around the border, as well as any lines that you have made, as well as The Fuse, who travels along the line that you are drawing. Once you have claimed enough territory, you proceed to the next level.