Shooter: Starfighter Sanvein (2000)

Sanvein is a fast-paced top down shooter where time is of the essence and every moment counts. The main computer of the self-sufficient space colony Utopia, called St. Schutz, has gone haywire. The goal of the game is to escape from Utopia. The game plays very differently from a normal space shooter. Each "floor" is made up of a series of interconnected rooms, and the player can choose any room adjacent to one they've cleared. For each adjacent room the player has cleared, their firepower in that room will be greater. Each floor has a number of boss rooms with a much larger and more dangerous enemy, each of which must be cleared to complete the floor. There is also a stronger power weapon which will recharge after use. All the while, a strict timer is counting down. When the player gets hit, instead of dying or taking damage, they lose time on the timer. The only way to get more time is to defeat a boss, so the player must balance between clearing rooms for greater firepower, and clearing bosses for more time.