Repulse

With a spaceship, the player shoots several kind of robotic enemies and spaceships. At the end of every stage (except for the first one), the player meets a huge enemy spaceship as the stage's boss. Player's spaceship is equipped with a limited force shield which allows it to resist any kind of attack, though energy drains both while its active and whenever the ship gets hit during. Power-ups are dropped by ally helicopters and spaceships, that bring to the player a new shot (much faster than the normal one) and refills his force field's meter.