Destroy an alien in level.

Destroy 5 aliens in level.

Destroy 10 aliens in level.

Collect shield power up.

Collect multi shot power up.

Collect power shot power up.

Score 10000 points in level.

Collect combo of 2 or more power ups.

Score 20000 points in level.

Destroy aliens halfway through the level.

Complete a level by destroying all aliens.