Really good entry! I'm really glad you had variance on the whistling with how much I ended up using it, the variance kept if from getting stale. The audio and visual design were really solid! If I were to suggest ways of improvement I would say a checkpoint system would have been nice, having to redo the entire game because of a small mistake was a bit harsh. The one way door mechanic was a fantastic idea to allow for interesting level design with this mechanic!
Great work!