This 2D canvas reproduces a real soroban-style abacus: seven rods, each with one heaven bead worth five and four earth beads worth one, in correct place-value order. Drag or click beads toward the beam to build any number and watch the running total update live, computed only from where the beads actually sit. Switch to Addition Tutorial mode to enter two numbers and step through the carry-over technique bead by bead: when a rod would exceed nine, it resets and passes one bead's worth of carry to the rod on its left, just as it works on a physical abacus.