Good but a glitch I found
In level 13 I jumped into the wall at the backside of the portal (making sure I wasn't missing any hidden items being the completionist I am) when I sunk into it. At first I thought that was a good sign, but then the screen didn't scroll with me. When I attempted to move back out I couldn't see my character. I'm not sure if I jumped off the visible screen somehow with the glitch, or just ceased to be in the active area of the game but... either way you may want to take a peek at it.