Robo Dug's game objective is to destroy cave-dwelling pests. This is achieved by inflating them to bursting point or by dropping stones on them. The player controls a tunnel digging robot. The robot dies if it is caught by a monster, burned by fire or killed by a falling stone. You have to pump the fire button several times to burst a monster. Half inflated monsters recover after a few seconds. Until then they are paralyzed. By skilfully exploiting this property, you can take on several monsters at the same time. In general, the enemies run through the tunnels, occasionally they turn into "eyes" and slowly ghost through the earth.