You can use the following example as a template for building your own game. It's based off the classic arcade game "Asteroids", you may however modify it into a completely different style of game.
You may also choose to start your game from scratch, but be aware that this is more challenging.
At minim your final game should include:
Helpful Links
http://www.lostgarden.com/2006/10/what-are-game-mechanics.html