I loved how fluidly the sprite work and cgs worked together. If I understand correctly, different people were responsible for them. The user interface design also looked very refined, and the music fit quite nicely. There were several screen transitions I've personally not seen used elsewhere that pair well with the concept of the key. The sound effect that plays reminds me a bit of old 8 bit point and click games, though seemed a smidge too loud to the music by comparison. I enjoyed the pacing of the story, and would like to see a continuation of this universe.
I can appreciate staying on point with everything having to be contained in such a short story, but I was hoping to see some misadventures when trying out the key. For example, not figuring it out right away, or accidentally using it and going to the wrong place could give a bit of humor, and a slight deviation from the "I'm finally gonna say it" tone throughout.
When the wolf mentioned the gizmo and the mirror, my mind immediately went to the idea that the key would let him traverse into the mirror somehow, and he would find the answer he was looking for within it, expanding his world. I felt slightly disappointed that there wasn't a bit more buildup of tension again, as the MC just quickly figured out the answer in order to progress the story.
Please take that with a grain of salt, because I really enjoyed this one, and see how much work and care went into it. Those were simply two places I felt like I was expecting something more to happen based on the cues in the narrative.
The only other thing that caught my attention was during the scene where the mc wakes up. The quick transition from the dark background to the bright white letter hurt my eyes, and it took me a second to focus to be able to read the words. I would suggest either slowly transitioning the background to one less dark as the scene progresses, or doing a slower fade as the letter appears on the screen. Another option may be to do a sprite of the piece of paper in hand with the words on it, and updating with a few different versions where the words appear line by line, dissolving into each other.
Again, these are all very minor points. This was a well polished collaborative work, especially within the time frame!