Like Phoenix or Demon Attack set in a bat-cave, Bit-Bat is a fixed-screen shooter where the player controls a gun that moves along the bottom of the screen. The bats that flitter above pelt the player with lethal projectiles, and must be shot down for points: the lower they are when they're downed, the bigger the score bonus.

The grotto's other inhabitants also join in on the action: spider-like enemies that enjoy dropping from the ceiling at warp speed, and curious round blobs which zoom from left to right and slowly descend towards the floor. The difficulty ramps up as time goes on, gradually increasing the number of simultaneous baddies (and their shots' homing capabilities). An extra gun is awarded every 50,000 points.