The core is very polished. Graphics and sound are on point. I do, however, wish there was more depth to it. I feel like it's very easy to become overpowered and just kill everything. I had 100 heals by the time I had enough.
Some suggestions:
More enemy variety would be nice. Maybe some bosses or enemies with ranged attacks?
It would probably be a bit more fun if you had to stand still and wait for like a second to use the heal, kinda like in Dark Souls and similar games. It adds a bit of risk and tension.
Overall, though, I'm very impressed!