Interesting concept! I think this idea has a really good framework that could be expanded into something greater. Firstly, some extra sound effects when you get hit would be nice. Secondly, whilst I like the really powerful attack that hits in all directions, sometimes the feedback on it feels really inconsistent because there seems to be a delay between when you can attack again? Also it doesn't feel like there's any invulnerability period when you get hit, which made the fast slime-like creatures almost always end my run as multiple would dash into me at the same time, bringing me down to 1 or 0 hearts :(
I think having some way to offset the total futility of having no control when you are on 1 heart would be good to allow the player to more reliability clutch the situation and rebuild their hearts (e.g. some kind of buffed "last stand mode" when you are on 1 heart for 10 seconds) so being hit doesn't instantly cause the cascading total demise of a run?
Perhaps some way to be able to hot swap your abilities around so you can priorities which abilities you would sacrifice? Or maybe a "shield" ability that takes 2 hits to lose that heart? You can really expand this in a lot of ways! :)