Huh. I tried it in a different browser and it works fine 
Ugghh... however, when I actually tried to
load the demo it created, this is what I got:

Turns out that's all I can get with the .costume files I have, although the Sentinel file comes out fine.
This isn't the computer I played on though, I have a ton more samples on the laptop I can test out. Hopefully those work right 'cause I have a lot of .costume files from deleted characters I'd like to see again.