Some quick points: 1. If you are low health. Back track and kill the rats and ghosts for pots. 2. The game only actually saves when you take the gem for the next level. I did most of level 4 trying to retain poison but it didnt save.
Excellent puzzler! I feel like the "progression" is very linear though. It would be better if you could shape the outcome as opposed to simply completing every puzzle, I don't like the false sense of choice in the game.