Fathom is another great game from Rub Fulop, who programmed several other classic Atari 2600 games
Such as Night Driver, Missile Command, Demon Attack, and Cosmic Ark. Unlike his previous hits, this one is a slower-paced adventure game, in which the player alternates between playing as a dolphin and a seagull. The goal is to swim and fly through multiple screens, searching for starfish that will give you a piece of Neptune's trident. Once the trident is assembled, you can release Neptune's mermaid daughter from her prison at the bottom of the sea. The game is colorful and fun, but can become frustrating in its later levels.
Neptina, Neptune's daughter, has been imprisoned at the bottom of the sea by Titans. Your goal is to rescue her by locating the scattered pieces of a magical trident! You will need to take the form of a dolphin and a bird in order to locate the pieces that are hidden in the ocean and clouds. When flying in the air, there are several screens that have clouds flying by. Touch all of the clouds, and the trident piece appears! Other birds which are flying around will cause you to lose energy if you touch them accidentally. Underwater, trident pieces can be found by touching the sea horses. Octopuses, sharks, and a deadly maze of seaweed will get in your way and cause you to lose energy if caught! When you have located all of the trident pieces, the cage holding Neptina can be unlocked, but if you run out of energy first the game will be over.