Really liked the sfx, the retro style look and animations on this... I felt like I was back in the 80s (in a good way!)
I think it would've helped if there was a bit of a tutorial, or extra instructions at the start, just to just an example of what you're meant to be doing in the game... I got it after a few goes, but it was a bit overwhelming to start with.
Clearly you know about the level up issue, so yeah, that happened to me too - the upgrade and game over screen both came up and the same time, but the game still ran in the background (ended up getting a really good score, but still, I'm sure that's not what's meant to happen :) )
Really solid game concept and style though! I like the timed star hits, it's a bit like space invaders at the end as they come closer. Bugs aside, really nice game - I enjoyed it :)