I had fun, but...
Good concept, music is pleasing to the ears if it's your thing, graphics are perfect for the type of game.
Alright so I've beaten the game, and gotten all but the Crown of the Euphony Gods medal and I have 0 intention of ever getting that. Why? Well even with all the upgrades I can't begin to imagine the level of skill you would need to dodge all those energy balls AND the lasers in level 16. All the other levels, even the final boss seem like a cake walk compared to that. Maybe I just suck at the game but holy crap that was difficult enough to get through normally.
There were several times throughout the course of the game where I found myself flipping off my screen after completing a level, this in my opinion is a good thing, as there was an actual feeling of accomplishment. However what takes away from this is the fact that I had maxed out my level and gotten every upgrade I could have gotten by that point and it still wasn't enough. Then there's levels like 9 and 17 which I got through before I even realized what was going on. I just went all the way to the back of the screen in level 9 and after that it was just a matter of absorbing the maximum amount and then positioning myself to attack. What I'm trying to say is the difficulty isn't consistently going up. Speaking of which, the final boss was a bit too easy though I do like what you did with it. Last thing in the difficult review, the lasers get kind of hard to see coming especially with the coloration you have going.
Throughout the game, even in the level you intended for me to use time slow down it was pretty much useless. It may be my impatience but I found it to do more harm than good, it ate away at the energy gauge and I was still surrounded by an obscene amount of energy balls.
Last thing I have to nit pick is the controls. While playing sometimes my ship wouldn't respond and just start moving in one direction or not move at all, even after I click the game screen several times.