There are four enemy types. Spinners (appearing on all levels) move blindly towards the player, but cannot harm him even when touching, unless he walks into them. Clones (appearing from level 2 onwards) move pseudo-randomly, and shoot in the direction they were moving/facing. Cyberdroids (appearing from level 3 onwards) move in straight lines for a period. They change direction when they hit a wall, see the player, or after a certain period of time. They will fire towards the player. The fourth enemy type is Spook, the ghost of a previous entrant to the fortress. He appears if you spend too long on any one screen, moving towards you and ignoring walls. He cannot be destroyed, but may be paralysed if shot. Touching the electrified walls of the maze kills the player.