Steer a galaxy with one hand.
Webcam looks at one hand and tracks 21 landmarks live. The galaxy rotates if you close your fist, blows apart and re-collapses on your palm if you open it, and zooms when you pinch thumb and index finger. The whole thing runs in this tab. No data leaves the browser.
MediaPipe Hands · Three.js · 22'000 particles in a four-armed log-spiral · webcam permission required
Allow the camera
When the browser asks, allow the camera. The video feed never leaves this tab; only the landmark coordinates of one hand are sent to the renderer. If you do not want to give access, the galaxy below stays a still image with a fallback message.
How this is made
Two pieces working together: a small machine-learning model from Google's MediaPipe, which has been trained to find hand joints in webcam pictures, and a particle renderer that maps those joints into a 3D scene next to the galaxy.
What MediaPipe does
It looks at every webcam frame, decides whether a hand is there, and if yes, returns 21 (x, y, z) coordinates for the joints. The model runs entirely in your browser; the frames never go to a server. From the joints we read three gestures: closed fingers means fist, open fingers means open palm, distance between thumb-tip and index-tip means pinch.
What the galaxy is
Eighteen thousand particles laid out on a four-armed logarithmic spiral, plus four thousand more for the central bulge, plus three thousand background stars. The radial colour gradient runs from warm gold in the centre to cool azure at the rim, in the same direction the Milky Way actually does in deep-sky photography: old red giants in the middle, hot blue O-stars in the spiral arms.
Where the data goes
Nowhere. The video stream is consumed inside this tab and the joint coordinates are consumed by the renderer. We do not record, store, or transmit anything. Close the tab and everything is gone.
What could come next
Two hands instead of one for two-handed manipulation. Face tracking to let the user move the camera around the galaxy by leaning. A second mode where the galaxy is replaced by a Lorenz attractor, or by an atom and its orbitals. The infrastructure is here; the next page is a copy plus one change of scene.