Good use of the theme- although I feel a game with a mechanic like this requires really spot-on swinging/"grapple" physics, and at least for me I quickly ended up getting stuck on a platform with poor Dully hanging below and I couldn't figure out how to get back up. I was able to beat the game after restarting though (who keeps a [spoilers] in a prison where anyone could grab it?) and I did really like it. Good on you for completing a full metroidvania with 3 (or more?) upgrades. The art and sound were cute, as was Dully's thought process. Him and I both thought "Nah!" at the same time. I also really liked the maps on the wall with the X for "you are here". Well done!
Oh, and I loved the guards *aggressively* sleeping in their chairs. A very nice touch.