While admittedly, most of your concepts here are nothing new, originality is unimportant next to fun, and good lord, DN8 is fun. It begins simple, but GRADUALLY becomes more difficult - a nice touch, compared to the difficulty spikes common with Bullet Hell.
The "evolution" aspect is handled very well; each selectable adaptation gives you a distinct advantage that the other choice does not, and I more than once found myself thinking "oh, I should have picked that one instead." The boss fights are hard at first, but the true extraordinary challenge they provide at the end of the game must be seen to be believed. Although, I have to say, the procedurally generated music and enemies, while a cool idea, aren't particularly interesting to see or hear.
Congratulations, friend. Unlike SOME reviewers on here, I'm giving you a 10/10 because I truly feel you've earned it.