Tutorial, I didn't expect that, especially with storyline! It's really nice done, jere.
I have mixed feeling about graphics and UI style. In overwall, it looks good, but I see... inconsistency. Most fonts you are using, icons, buttons, borders are really smooth. But dialogue boxes, main menu, and minimap are pixelated / bulky / rough, like 8/16-bits era. It just doesn't fit each other. If I were you I'd stick with one style. Especially minimap is obtrusive, are you planning to change its design?
I love diversity between playing human and vampire (personally, I prefer the latter ones due that great-in-own-simplicity stealth system). Pace of transformation from human to vampire is surprisingly fast. It's not bad if the number of potions are sufficient enough, but I can't evaluate it now.
Gameplay is really smooth and pretty dynamic - at least early game, I didn't manage to reach midgame yet. The sun rays mechanics is great, for both killing vampires and being vampire.
But OK, I grumble a bit, but I had really fun time with GKH. I reached 6 level already, just decided to unlock alchemist.
Unfortunately, I encountered issue(s). One or two only, nothing major, so it's good info I think
After toggling fullscreen (so, entering windowed mode), the side scroller doesn't adapt well for new screen height -
it's necessary to manual resize screen height. I encountered similar issue when I was trying to enter fullscreen again -
it looks like window size changed, but workspace not. It fixes self when player re-enters main menu.
The down arrow of scroll bar always hide self out of window. When I resized window to see that UI element, then back to the game and back to the options menu again, the down arrow was out of the visible screen again.
Probably I could resizing window ad ifninitum.