This is very interesting! The intro was really funny and a great hook, though the the brown key was very hard to see in the cutscene. Actually, the game was probably just too dark, which I understand to contrast with the lava but still. Also, I found on my own that shift is run but I don't think the game said it in the instructions. You should add that to the description along with the rest of the controls for convenience. I got up to the chair arm and died, didn't find any keys :(
Also I'm not sure how your programming coded the mouse controls but in my browser the sensitivity is WAY too high, I'm guessing something should have been multiplied by Time.deltatime or placed in FixedUpdate() when finding angles and such.
Also as a note, the embedded viewport should have 30 pixels more than the game resolution height so the banner under the game isn't obscured.