value cell with x, y, radius, teeth, ratio. The cursor position is two sensor cells (cursor.x, cursor.y). Clicks write to a listener cell that appends to the ledger. The ticks formula counts how many rotations have happened. The 5 eras show how different cultures solved the same problem (counting time) with different mechanisms — a 17th century verge escapement looks nothing like a 20th century quartz oscillator, but both are cells in the same sheet. The metaphor: cells are gears. Connections are shafts. Formulas are escapements. Listeners are bells. Try clicking different gears. The downstream cells react. This is the spreadsheet-as-runtime made visible.