Avoid or Destroyed Not bad!
This game is pretty good; gradual increase in difficulty, tails to show movement/speed, basic powerups, different movement in different enemies...you have the basic components of a great dodging game.
There are too many areas on which you can elaborate though. First off, there are only two powerups. You can add maybe something that lets you shoot for a limited time, something that makes you smaller/bigger, a "smart bomb" that destroys all enemies on the screen, etc. The game is also way too short. In later levels, you could combine different enemies to further confuse and frustrate the player. Other than that, good job!