Devil fish is a single-screen maze game where the objective is to kill the pursuing octupuses, and collect the nine pieces which make up the picture in the centre of the maze. You kill the octopuses by trapping them in the gates positioned around the maze and running over them while they are trapped, and then you return to the log cabin which appears. When you return to the ninth cabin, you complete the picture in the centre of the maze and advance to the next screen.

The enemies appear from one of two bases located at the left and right sides of the screen. There are also tunnels located on the left and right which can be used as a shortcut from one side of the screen to the other.

Sometimes an octopus is too small to get stuck in the gates, so you must fatten it up by making it eat one of the fish you are carrying by dropping it in front of it as bait. The octopus then increases in size and will get stuck in the next gate it moves into providing the gate is small enough.The size increase does not last indefinately however, and after a short period of time the octopus reverts to its previous size.

The enemy octopuses come in three sizes, the smallest of which cannot get stuck in any gates and the largest of which get stuck in all types. Gates with two sides will trap medium and large enemies, and those with only one can only trap large enemies.

Your supply of fish however is limited to a maximum of 15 carried at any time and is displayed in a graphical bar at the bottom of the maze. You can collect extra fish by picking them up when they appear in one of the two resupply points on each maze. Points are scored accoring to the type and size of octopus destroyed and bonus points are awarded each time you return to the log cabin.

The octopuses can be any of four types, denoted by colour (which are currently incorrect in MAME) and each type moves at a different speed, the fastest of which moves at the same speed as you.

An extra life is awarded for 10,000 points.

Try to lure more than one octopus at once into a gate to increase your score.

Don't delay too long on any screen as the next screen will start with faster enemies.

Wait on the other side of a gate where you know a pursuing octopus will get trapped and pick it off as soon as it gets stuck. If another octopus was close behind the dead one, move back over the gate and kill it when it gets stuck.

Since the octopuses always pursue you, you can use this to get them to follow the path you want.

Don't collect extra fish at the start of a screen since no more than 15 can be stored, and any extras are lost.

Use the side tunnels to move across the screen, and the enemies don't often pursue you through them.

When being pursued by a fast and small octopus drop two fish in front of it, taking it to its largest size and slowing it down.