I really enjoyed this. The action is frantic with lots of enemies on screen, but the player attack is powerful enough that you can deal with them. Nice, simple design and easy to understand how to play.
However, after the second level, the counter kept resetting to 5 over and over, with the timer in the corner going into negatives, so I couldn't progress. Tried again to see if it was a one off, and this time it happened after the first level instead.
Also, the game doesn't appear to have a way to exit (after the title screen), because there's no way to return to the menu, or switch to windowed mode. I had to use task manager to exit.
Hopefully you can fix the bug I mentioned, because it is otherwise a really nice game and I was looking forward to the next level.