The premise is simple but strangely fun. It could be better if it was faster paced.
Simple and Addictive
This game is beyond basic, but is still entertaining and successful. It's very much in the spirit of the 8-bit era.
What it needs most is music and sound effects. The graphics could also be a little better -especially the color scheme.
Schematically, you should have both WASD and arrow controls for left handed users. You should also have a title screen or introduction of some sort.
The final addition to make your game amazing is to add a high score at the top of the screen to keep the player struggling to best himself/herself.