I've noticed that with a couple games, this one included, the mouse is recognized just fine by the flash game, but the keyboard is not. So while the game loads and I can click on the play button, I cannot do anything beyond that.
There is one main issue with this game for me. It is extremely laggy. Even with the graphics on low, which makes playing this game not fun. Fix the lag and it'd be a 5/5 easy, but until then this will only remain a 3/5. It's a good game and is fun, until the waves get too large and the game near locks up.
I love the URL option; this adds what the first was missing. 5/5
If you like Trance, I'd suggest any/all of the songs off of:
http://goukisan.newgrounds.com/audio/