The atmosphere, music, and animations all added immensely to the experience.
With more time I would love a full adventure of this, but one thing to note is that I don't think you need to hide what the success number is? I think the suspense of the die roll might be heightened if a player knows what they need to roll. Right now, the "Yay" or "Oh no" moment comes through reading the text, and not the moment the result is shown.