A free program for Android, by GASP.

Defender is a remake of the classical Galaga/Galaxian game. Galaxian was developed and released in 1999, and it became one of the most profitable games of its time. It has been ported to numerous platforms, so why should you give our version a try?

Defender is a tiny download of less than 100 KB. You can play it on the phone or the tablet.

The objective of the game is to defend the galaxy against alien invaders. To accomplish this, you will need to shoot waves of alien ships, destroying all the enemies in their path. 

Defender includes several modes of play. In addition to the main campaign mode, there is a practice mode that allows you to practice shooting and improve your score.