I really enjoyed playing this! The slowing fields mixed with the visuals is a great mechanic. Once I got around 100 points it started getting really hard to kill the bad guys and I didn't make it much further. I think the strength of the shots needs to go up a little higher with each level to help the balance a bit.
The graphics work well for the theme, and the audio helped add to the experience without becoming annoying or repetitive. You did a fantastic job putting this all together in the three hours.