Problems I had with it:
Blue enemies that drop bombs when they die. The bombs look like a power up (The speed up power up) and are not easily distinguishable. And it really puts you in an awkward position a lot of times that just feels cheap rather than good enemy patterns.
No bar showing when you will lose your power ups. Very frustrating when you're about to take out a huge horde of giant ships that take tons of shots to kill and your weapon power has just run out.
Very little hit invincibility. Sometimes you're SOL and don't have a speed up and a wave of unavoidable shots are coming at you and you take all that damage. At least give me some substantial invincibility after being hit.
Good game. Loved the concept. Just fix these flaws.