Complete a level by destroying all aliens.

Score 20000 points in level.

Destroy aliens halfway through the level.

Collect shield power up.

Score 10000 points in level.

Collect power shot power up.

Collect combo of 2 or more power ups.

Collect multi shot power up.

Destroy 10 aliens in level.

Destroy 5 aliens in level.

Destroy an alien in level.