Escape from the Planet of the Robot Monsters is an Atari coin-op released in 1989, ported to Amiga, CPC, Atari ST, C64, DOS, and other platforms.
The game was designed by Mark Stephen Pierce, also known for Klax and Dark Castle. This excellent Amiga conversion was developed by Teque, the same studio that made Brutal Sports Football, Shadowlands, Laser Squad, and many other titles.
Escape is a shoot-em-up for two players (yes, single-player is supported too, but co-op is much better). Unlike other 2-players shooters like Alien Breed, Escape from the Planet of the Robot Monsters uses isometric graphics. The sprites and background are detailed and colorful in a lovely cartoon style, similar to D/Generation.
The goal is to free all the prisoners, especially doctor Sarah Bellum, who are hostages of the evil aliens "Reptilons". Initially, you will have to fight their robots, but later, you will face the aliens.
The only real problem is that your gun can fire only in the eight directions of the joystick, while enemy fire can reach you from any direction. That's why the difficulty level is high—another reason why you should play it with a friend. Enjoy!