The player controls a green man. Using a joystick and a fire button that activates a laser weapon, the player navigates through a simple maze filled with many robots that fire lasers back at the player character. The player can be killed by gunfire, by running into a robot or an exploding robot, by being electrocuted by the electrified walls of the maze itself, or by being touched by the player's frenzy, Evil Otto.
The function of Evil Otto, represented by the jumping emoji, is to speed up the pace of the game. Otto is unusual in the games of the period in that he is indestructible. Otto can walk through walls with impunity and hunt the player character. If the robots remain in the maze, Otto moves slowly, at about twice the speed of the humanoid, but he speeds up to match the humanoid's speed once all the robots are killed. Evil Otto moves at the same speed as a player walking left and right, but he can move faster than a player walking up and down; thus, no matter how close Otto is, the player can escape if they can avoid moving up or down.
The player progresses by escaping the maze through a hole in the far wall. Each destroyed robot is worth 50 points. If all the robots in the current maze were destroyed before the player escaped, the player gets ten points per robot. The game has 65,536 rooms (256×256 grid), but due to random number generation limitations, there are fewer than 1,024 maze layouts (876 of which are unique). It only has one controller, but two-player games can be played by alternating the joystick.
As the player's score increases, the colors of the enemy robots change and the robots can have more bullets on the screen at the same time. Once they reach the on-screen limit of simultaneous bullets, they cannot fire again until one or more bullets have exploded; the restriction applies to robots as a group, not as individuals.
A free life can be awarded at 5000 or 10000 points set by the internal DIP switches, with no extra lives after that.
The voice synthesizer in the game generates speech for robots during certain game events:
- "Coin found in pocket": In attraction mode, especially when displaying the high score list.
- "Intrusion warning! Intrusion Warning!": Said when Evil Otto appears.
- "Humanoid must not run" or "Intruder must not run": The player is heard leaving the room after each robot is destroyed.
- "Chicken fight like a robot": Heard when the player leaves the room without destroying every robot.
- "Got a humanoid, got an intruder!": Heard when the player loses a life. (The "got the intruder" part is a third smaller than the "got the humanoid" part.)
Random robot chatter plays in the background, with phrases usually consisting of "Charge", "Attack", "Kill", "Destroy", "Shoot" or "Get" followed by "Humanoid", "The intruder". "," this ", or "chicken" (these only act if the player received the message "Chicken, fight like a robot" from the previous room), making sentences like "Attack it", "Get the humanoid", "Destroy intruder", "Kill the chicken", etc. The speed and pitch of the phrases range from deep and slow to high and fast.