The Gate — puzzle rooms & a climb to the roof
A password gets you through the door, then four rooms — the Gate, the Tomb, the Archive, the Abyss — each one a puzzle. Solve your way down and the payoff is a Donkey Kong-style platformer: climb the ladders to the rooftop exit before the walls seal Nutkin in for good.
Needs the password. The puzzle flow is the game, so the front door is locked on purpose — send friends the password along with the link.