Your gunner bounces by itself. Steer left and right to land on the next platform: arrow keys or A/D, a controller stick, or on a phone drag sideways anywhere (or tilt). Go off one side and you come back on the other.
It also fires straight up on its own. Waves of invaders march side to side, step down at the edges and drop bombs. Shoot them before they reach you; you can shoot bombs down too.
Climbing pushes the fleet back up, but only partly: keep climbing and keep shooting.
Fall off the bottom, take a bomb, or touch an invader, and it's game over.
PLATFORMS
Solid ones, moving ones, dotted ones that crumble after one bounce, and springs that launch you high.
SCORE
Invaders 100 / 200 / 300 (the bigger, the higher up the fleet), the mystery ship up to 3000, clearing a wave 500+, bombs 25, and 1 point for every 4 pixels you climb.
Power-ups sit on platforms: rocket (blasts you upward), shield (takes one hit), triple shot (10 seconds).