Only a few minor things I would fix.
First off, the ship itself is too large for a shooter. Ememies shooting straight down are impossible to hit without being hit yourself, just because of the sheer width of the ship.
Second, mouse controls. Enough said.
Third, I noticed that, when you die, you keep 1/3 of your EXP and items. This would be great, however.. I recently died on a level. I had collected 820 EXP and 40 gems. I kept 205 EXP and 10 gems, which is NOT 1/3, that's only 1/4.. 1/4 kept would be fine, just make sure you're telling us the correct amount.
Other than these three things.. great game! It's an enjoyable and challenging play, and I look forward to a sequel!