Deep Blue

Deep Blue is an underwater themed shooter developed by Pack-In-Video for the PC Engine and published in Japan in 1989. It was translated for release on the TurboGrafx-16 and published in 1990. In it, the player controls a submersible fighter shaped as a freshwater angelfish that must fight through waves of mutated marine life.

The player operates a fish-shaped submarine in an effort to defeat sea creatures. The submarine can benefit from collecting three different types of power-up items. There are four stages in total, with a boss at the end of each stage. If the fourth boss is defeated, the game starts over on the first stage at a higher level of difficulty. There are three different weapons; bubble bullet, foam bullet, and flash bullet. They can be powered up to 3 levels of power, but if the submarine is damaged, your weapons are immediately reduced to the lowest level.

The submarine can actually sustain a lot of damage. As the damage accumulates, the color of the submarine's eyes changes from blue to green, then to yellow, and on to red. If you receive too much damage while the eyes are red, the submarine is destroyed and the game is over. In addition to an item that you can collect to restore some of the damage you've taken, your ship will also heal automatically if you stop firing your weapon for a certain period of time.

All the enemy characters that appear in the game are underwater creatures, but since they are real creatures as opposed to mechanized ones like in Darius. As a result, they do not shoot bullets at you like normal shooting games. Their only means of attack are to hit you with their bodies. Boss enemies are no exception, and in addition to ramming, some of them will spit out small enemy fish to attack you.

Ultimately, this game was considered too difficult for casual play. Since enemies don't attack with bullets, the game challenges you with sheer numbers of opponents that frequently overwhelm you. Since one successful attack reduces your offensive power to the lowest level, it's extremely difficult to maintain an advantage against the enemies.