And 2 more things - I didn't grind the levels, but had every upgrade possible at level 10. Maybe make so only the boss gives red gems as a reward. And maybe make some congrats screen after beating the last lvl.
A little bit too easy, especially the boss levels - you can just spam missiles at them.
It's also difficult to see what is an enemy bullet, a mine or a harmless background asteroid, there's too much going on. Maybe make only 2 colors for bullets - your and enemy's. Or make less enemies at a time, but a little bit tougher, stronger with more hp.
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 "Paradise v1"){kind=icon}
 "Ether War"){kind=icon}
 "Z-Rox"){kind=icon}
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