Finished the demo. Ran into some strange things, like a jigsaw piece that was overlapping the mirror from the start and wouldn't be moved, as well as sometimes picking up several pieces at once.
Being sent back to the start after getting the second riddle wrong was also a tad frustrating.
Spacebar also seemed to be an undocumented control to advance text. I kept hitting A when talking to the hand mirror, and thought I'd gotten stuck in a dialogue loop. Turns out I was just restarting the dialogue every time until I randomly tried to hit Space.
For what it's worth: Audio worked fine in the web version.