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The 3×3 grid on the busy line moves one cell at a time. A lit cell runs clockwise round the outer eight cells, with a short fading tail. The centre pulses once a lap. Each cell holds its level for a whole step, so the grid reads as cells, not a gradient. Under reduced motion it stays still.

In the app

The grid on the busy line while a turn runs.
The grid on the busy line while a turn runs.
The lit cell at the bottom of the ring.
The lit cell at the bottom of the ring.
A step later it has moved clockwise to the bottom left, and the cell it left fades behind it.
A step later it has moved clockwise to the bottom left, and the cell it left fades behind it.