cosignal parent
The site seems incomplete. Tibetan does have 5 vowels, and it looks like the non intrinsic vowels are written at the bottom section of the view, but I can't get them to work. I assume the intention would be that you click one of the other vowels to toggle it, but it no worky.
I don't know who created it, or if it was part of a larger proto-Duolingo language product.