Some idea's
1. Tutorial:
Can't buy things
Can't kill the target whit 10 points
Can't use WASD keys
2. Real Game:
When hit by a laser, shake the screen?
Q for quality, not a camera icon
Keys shown at the start
More bosses
3. Pause menu/Upgrade Menu (space)
Rollover for detailed info.
More stuff ofcourse.
5/5'd 9/10.