Nice game! well done, I love that it's complete.
One suggestion which might be hard to do: if you can make the white board writeable and have some number recognition that detects when the user draws the answer "4" on it to activate the door, that might be interesting :) an easier thing is to have like 9 dots grid and user has to connect them using the pen to draw 4 (that might be more doable)
Also in the last hallway there was a 2d drawn door, I wish if it was interactable, it would be a cool mechanic