Yet Another Spaceshooter Lite

Simple, endless space shooter:
Navigate your spaceship through the increasing number of enemies just by touching the screen. Collect extras and try to survive as long as possible. Share your score with your friends with GameCenter and challenge them.
Probably not one of the best games available in the AppStore, but developed completely in my spare time as a hobby project. Please let me know, if you have ideas how to improve the game.
If you want to know how to develop a simple game like this, check out my tutorials at: http://developerplayground.net
A link is available inside my App.