Make an interactive real-time black hole visualisation in one web page: a spinning black hole with a glowing accretion disk, gravitational lensing that bends the starfield and the far side of the disk over the top, Doppler beaming that makes one side of the disk brighter, and a photon ring. Drag to orbit the camera, scroll to zoom in towards the event horizon. Add a small panel to change the black hole's mass and spin and the disk temperature, and short labels that explain what you are seeing. It should look like a film shot and run smoothly in a normal laptop browser. It should feel stunning the moment it loads.