Duuude this was amazing! It took me XX very enjoyable minutes to solve the whole thing. Such a cool moment when you (SPOILERS) think the last key isn't even needed or that you can brute force it but in the end of course it is and you can't (and that music punch during the arrows bit is fantastic!). My solve order was: tree, IV dudes, tic-tac-toe (took me a while), II-headed dragon (very tricky!).
My II extremely minor complaints that barely detracted from the experience at all: the window by the staircase looks a lot like a door and the II "stripey" key/lock patterns look a lot like each other. Both had me clicking on the wrong spot C times haha
Congratulations on another great one! I'm so glad I found your games. If you ever implement multi-language in your engine and need strings to test the feature, I'll be glad to translate a small game like this into Spanish for free.