I think this one asks you to pay for it after a bit. Not that there's anything wrong with that. Just felt bad about getting a little bit in, and then being hit with a decent pay wall.
I paid for it, was worth it for me. Reason: I did vimtutor 4 times and was learning but found it super painful/boring, but really wanted to learn vim keybindings. Vim adventures made learning keybindings and muscle memory just tolerable that I could do 1h in the evening even after a long/busy/tedious day. I probably would have persisted learning vim keybindings without it, but it definitely made doing so less painful.