This was great! Very hard early on, without many corners, but the fact that you keep progression helps with that a lot.
I found I was quite often rotating cards when I wanted to drag them, and vice-versa. Would you consider using right click for rotate?
I like the little blue guys. They're very cute. I wonder if there might be some mechanical space in having tiles that trigger when walked on. For example, a monster tile that gives you a useful tile when played, but is dangerous to walk on, so you'd be looking for side spaces to put it in. Which is to say, I think this core mechanic has a lot of potential.