Tap on the screen to shoot towards a direction. You must destroy all visible aliens in order to advance to the next level and unlock more weapons, upgrades and aliens. For each upgrade, you can read the in-game instructions and you can upgrade all weapons
Galactic Missile Defense is a strategy tower defense ( TD ) game set in space, where you are in charge of 3 secret anti-missile technologically-advanced bases that are the last hope to save Earth. You can upgrade any anti-missile base with a variety of weapons and boosters but you must be careful as each choice requires strategy and skill. Be prepared for quick decisions as the action increases dramatically once you reach the higher levels!