Such a pretty game! The sprites are very pretty, and they also work very well in a game context.
I do think that the mechanic of gaining health upon dying can be quite dangerous - you do help players who are struggling, but this does bite back in the final battle. Since players who die more often are probably not as good at the game, that'll mean they'll have a harder time beating the final boss.
(unless there's something in place where the player's boss will get more HP when they die, too - admittedly I haven't checked)
But still! The concept is cool, and I really like the idea of having to suffer something negative from taking something positive early. It creates some interesting choices!