Great entry! In particular, love the choice of colors. They work really well both to emphasize the "spooky" vibe and to call attention to important in-game objects.
The combat mechanics are really fluid, and fell squarely in that sweet spot of "easy to grasp but hard to master" for me. I also really like the idea of representing entities that take more than one hit to kill (both you and the enemies) by having their extra hit-points float behind them, really creative! I did find it a bit confusing at first when seeing it on an enemy, because it seemed like it would drop a heart when killed, (maybe enemies could use a slightly different sprite for their hit points?) but once it clicked I found it very clever.
Unfortunately the boss of the final stage seemed to get stuck outside the level for me, so I couldn't complete the game. But I really liked what I saw! Nice work!