Negative health bug? I considered it a feature. I wish I could hear how you would prefer the game to handle death? You either use, or buy, potions, or you restart, yourself.

You got hit getting to the shop directly above the spawn point? It’s just a rat and a snotling between you and it. Both of which you can jump.
I’m not sure what you mean by “skill gapped on the stairs”? Perhaps my implementation of stair mechanics did not fit your understanding, which seems more extensive than mine, of the Castle Vania series? Or do you mean the boss on the final stairs?
The resolution was fixed at 1024x896. Which is exactly 4x NES resolution. I had to consider 1920x1080 screens, which is probably what 90% of people use. With more having higher, than lower resolution.
On MS Edge, zooming in and out does change the game’s screen size, so I think I’ll leave it at 896 pixels tall and maybe advise of this workaround, somewhere.
Thanks for playing and reviewing!