modified

![background](https://f.cloud.github.com/assets/6157774/2180566/03e5d920-9723-11e3-8a31-d8cb26d292bd.png)
![enemy](https://f.cloud.github.com/assets/6157774/2180567/03e7661e-9723-11e3-94ba-722dcc003367.png)
![bullet](https://f.cloud.github.com/assets/6157774/2180568/03e78496-9723-11e3-9630-6492004b0ca9.png)