Displayed image is not of the actual cartridge.

Hybrid Heaven takes many elements from standard 3-D action-adventure games, such as Tomb Raider. The player can move in any direction, jump, crawl, climb, and shoot. The player must solve puzzles by disabling electronic weapons or through skillful manoeuvering.
However, when battling a monster (called a "biological weapon" in Hybrid Heaven), the game switches to a completely different mode. The player is constrained to a small room and can no longer jump, crawl, or climb. The monster and the player move around for strategic position in the room. When they are close enough, and have built up enough energy, one or the other will decide to attack. At that point time freezes and a single round similar to a role-playing video game turn ensues: the attacker picks an attack from a list, the defender picks a defense, and the results are displayed. After the attack, both monster and player return to jockeying for position in realtime. All of this can happen within seconds, which keeps the action flowing more naturally than in most RPGs.