Bullet hells aren't my genre but I still had a good time; enemy variety seems pretty important to this kind of game and Renatus delivers, with the enemies looking and feeling different and having different roles on their "team" against the player.
All the audio was there, and I enjoyed it; I do wish in an entry with so much of one act so fast (shooting in a bullet hell for example) that there was >1 piece of SFX for it. pewpewpewpewPEWPEWPEWPEWPEW will be in my dreams tonight.
The core mechanic of "you get *significantly* better after each death, but you have finite lives" is awesome, I love a good 'shoot the moon' mechanic in games and this definitely fits the bill. You can stay weak but preserve lives, or get risky but be as strong as you want, as fast as you want. This is a much more fun way to allow a player to choose difficulty for themselves than, say, a menu setting! However, I could not tell how you were supposed to know how many lives were remaining (except having played before).
This might just be that I'm not used to bullet hells, but I kept trying to get the environmental kitsch to do stuff. Oh, a green carpet, I wonder what that does vs. a blue one! Oh, an open chest, I wonder if that's got something in it for me? Ultimately no, the game is you and the enemies - which is fine, but I wish I'd figured it out sooner!
Overall: easy to pick up and play, not so easy to beat. That's how it's meant to be IMO!