updated with extra features:
1) you now get a new life at every 100 scored
2) text is printed when SAM launch warning at bottom
3) the missile smoke only extends 3 blocks below the missile so is (remotely) possible to dodge it from below. You can still shoot the missile if you're skillful enough :)
4) ground is no longer "shootable"
5) enemys now bigger but less of them (mercy!)
Stay posted for future updates