The smoke room.
The smoke is a real fluid simulation, solved on your GPU every frame: MacCormack advection, buoyant heat, vorticity confinement, and a Jacobi pressure solve keeping the flow incompressible. The counter and the bottles are solid cells inside the solver, so the flow has to go round them. Light is marched from the lamp through the smoke for every pixel on screen — smoke and glass both throw true shadows. Move the lamp and watch them swing. The room remembers, too: smoke stains the walls a little more each visit, and a reset doesn't wash it off.
drag — stir · click — puff · C — window · M — sound · P — take a print · R — reset · shift+R — scrub the walls
This room needs WebGL2 with float textures, and your browser has the lights off.