I'm glad to hear others had difficulty with the birds - I assumed I was just rubbish at platformers! I really enjoyed working out the maths puzzles in the middle though!
Beautiful art, and beautiful prose!
The truth behind the mystery was really clever, although there was definitely a bit of 'deus ex machina' in the protagonist's solution.
My only other thought was that it felt unintuitive to me that the 'crouch' key was on the row above the 'jump' key on the keyboard - since jump feels like 'up' and crouch feels like 'down' I would have expected crouch to be on the row below jump.
But overall this was a really fun ghost story experience!