Soroban

click a bead — earth beads count toward the bar, heaven counts 5

A real soroban, not a picture of one. 13 rods; each has one heaven bead worth 5 and four earth beads worth 1. A bead counts when pushed toward the reckoning bar. Click a bead and the beads between it and the bar move with it — true soroban physics.

Set to a number

Calculator — operate on the current value

Worked examples — watch it carry

Skin

Digit of a rod = (heaven down ? 5 : 0) + earth beads up, always 0–9. Unit dots mark every third rod (the classic soroban convention). Skins change only the wood & ink — never the value.