A quick foreword: I am terrible at shmups and twinstick shooters at the like -- but in lieu of that and looking for new experiences, I gave this a try.
Music
I actually can't say enough good things about the game's music! It's filled with a lot of 16-bit goodness that leans heavily on Mega Drive soundchip trappings, which compliments the visuals wonderfully.
Gameplay
I played on the lowest difficulty and didn't get very far due to time constraints, but of the two levels I played, there is really interesting enemy and boss variety. Enemies will come from virtually any direction so you have to keep your eyes peeled. The three different shot abilities have different utilities as well, which forces the player to actually pay attention to what firing modes are best suited to the situations they're in.
The weapon upgrades are substantial too -- the only thing I don't like is that you lose them on being hit, but I guess that raises the skill ceiling and rewards good gameplay.
Controls
Please play this with a gamepad, a keyboard setup just doesn't really do it justice whatsoever.
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I'd heartily recommend this to anyone looking for a hidden gem in the shmup genre -- it's very accessible, which is highly unusual for a genre that's not normally known for pulling its punches with difficulty settings.