Not bad, but...
It needs a bigger goal! This game just seems endless..:( Here are some ideas to improve the overall game play.
-Levels, skills, weapons?
-A target amount of enemies to kill before a time limit? (Each level should have a different goal).
-Surviving an amount of time?
I really like the sound effects. The music was...alright. The background was okay. Please make a second version with some improvements, I look forward to playing that...:) I rated 3/5, 6/10.