simon says: the dungeon crawl experience :D
Interesting mechanic! The invisible walls came out of nowhere, though. Was especially brutal due to the music tiles being invisible as well (as far as I could tell). I'm glad I stumbled into an invisible wall by accident because I was getting close to thinking something was wrong and quitting.
I enjoyed the atmosphere. I think the length was just right, I don't think I would've continued if it went beyond 4 levels. If it were a longer game and there were other compelling reasons to keep playing, I would've busted out some pen and paper for this lol