I think I know why it does that. Google Chrome is the default browser, so Internet Explorer runs without "add-ons" which I assume might have an effect on the upload thing, as I cant use YouTube on it even. Tried on Google Chrome and it worked! Here is the download!
It doesn't, unless your copy is somehow glitched. If you consider "ignoring masks" walking into walls, falling through stuff, etc, then that's a glitch in your coding.
No, it's actually the opposite.
I tried to make it so you could fall into smokestacks, and gave them a mask that looks like the normal sprite, just with no smoke and a big hole in the middle. For some reason, You can't fall through it at all. It's just as if it didn't HAVE a mask.