The game is awesome.
Now when I played it both here and on Lexaloffle I can what was that strange error. It's about your max HP upgrade. If you had at least one on your previous run on Lexaloffle you will get error and will be forced to reset cartridge (thankfully your unlocked characters are saved). But here, on itch your +1 hp are saved between runs...Which isn't that good if want to keep challenge, but you can always reset.
Hope to see some updates. Gameplay is fun but some updates are obviously less useful than the others, I'm talking not about weapon tiers (still I don't know why triple stole counts as 5) but about "trinkets". Cleansing (even if it's grey one) is a must, but thing like +1 if staying close/far is the weakest of them all... maybe poison is worse (I still can't be sure how it works, but it can't destroy hydras)
Here is my 4th run in a raw. As you can see it's day 1 but I already got +8 hp from my previous runs.