Clear all the egg cells. Shooting a big one splits it into smaller ones. Running into any of them costs a life; you start with 3.

Keyboard

Left/right arrow keys (or A/D) rotate, up (or W) thrusts, space fires. P pauses, M toggles sound.

Touch

Use the four on-screen pads: rotate left, rotate right, thrust, and fire.

Worth knowing

You keep drifting until you thrust the other way, and the screen wraps around. Blue pills upgrade your gun; dying knocks it down one level. Clearing a wave pays extra for speed, accuracy, and not dying.