E.S.P. is a side-scrolling shooter. There is no plot in the game - the player controls a robot-like flying device, shooting his way through hordes of organic and mechanical enemies. The player-controlled device can be moved in four directions, and also adjust the angle of fire. There is only one kind of power-up in the game (a floating letter P); eating it will expand the range of the device's fire and also grant it an additional weapon (shooting blue spheres); the player can then adjust the fire angle in such a way that the device can shoot in different directions with different weapons.
