The iPhone Duo fold, on a MacBook

The part people remember is the material. The display does not fade out or slide away. It lifts, leans, and goes milky at the top while the bottom stays almost clear, the way a real pane of etched glass would as it tilts away from what is behind it.

That is the effect Mac Duo recreates, and the reason it is worth recreating on a Mac at all: a MacBook already has a hinge you move with your hand, which is exactly the input the effect wants.

A phone gives you a closing gesture and then plays an animation. Mac Duo has no animation to play. It reads the angle of your lid and draws the fold that matches it, so moving the lid a centimetre moves the glass a centimetre's worth. Stop halfway and it holds there. Reverse, and it unfolds along the same path it came down.

Because the same angle always produces the same glass, opening retraces closing exactly. There is no timed fallback, and there is nothing to trigger: the lid is the control. How Mac Duo builds the fold covers the pipeline from sensor to screen.

The glass is built out of your live display and rendered with Metal, so windows and wallpaper move as one surface rather than as layers sliding over a still image. That is why Mac Duo asks for Screen Recording permission, and why it cannot run without it.

Capture only runs while the lid is actually moving. The moment it settles, capture stops.

This is the one real dependency. The fold is driven by a continuous lid-angle sensor, and not every MacBook exposes one. A Mac that has only the magnetic sensor that tells it the lid is shut cannot drive the fold, because that sensor reports shut or not shut rather than an angle.

Which MacBooks work with Mac Duo has the model list and a one-line check you can run in Terminal before you buy, and what the MacBook lid-angle sensor is explains the hardware behind it.