New version - Demo 1.4:

The Arecibo message was a radio message that was beamed into space at a ceremony to mark the remodeling of the Arecibo radio telescope in 1974. It was aimed at the globular star cluster M13 over 25,000 light years away. The message was received by the Charonians a race of aliens spent on conquest.

You are just one soldier amongst many fighting the alien invasion and defending earth cities.

Authors notes:

1. Some ships are harder to kill (require more than one shot)
2. Some ships will make it more difficult for you to "lock on" to them by moving away from your crosshairs.
3. Missles that lock on target, even if it moves.
4. Missles that are smart, fire a few extra and they find a new target.