Galaga.
Defend the sector.

Collect capsules: T = triple shot · R = rapid fire · S = one-hit shield · X = side cannons · W = twin fighter. One weapon upgrade at a time; a shield can accompany it. Weapons last 8 seconds, shields 12. The first capsule drops after 20 kills, then every 24 (one on screen). Every fifth wave ends with a boss that drops one capsule. Hold Space or the touch Fire button to shoot. Twin fighters have a larger hit area. M = homing missiles. Missiles automatically track enemies, fire slowly and expire after 2.5 seconds. Rescue the dogs by touching their capsules: +750 points, at most once per five waves. Hitting a dog capsule with your own shot costs 5,000 points, even below zero.