Abacus

Tap a bead to move it. Like a real abacus, the beads between it and where it goes move with it, and tapping a moved bead sends it back with the ones beyond it. You can also drag a bead. On a keyboard, Tab to a row or column, then use the arrow keys, Home and End, or type a digit.

The counting frame has 10 rows of 10 beads. Every bead you slide to the left counts one, so a full row is ten and the whole frame is 100. The first five beads of each row are solid and the next five are rings, so fives are easy to see. The soroban is the Japanese abacus. Each column is a place, from ones on the right to millions on the left. The bead above the bar is worth 5 when it is pushed down to the bar, and each bead below the bar is worth 1 when it is pushed up to it. So 7 is the five bead and two ones beads.

Free play shows the number on the abacus. Show me sets the beads for a number you type, one place at a time, so you can watch how it is made. Practice asks for a number: set the beads, then Check. A miss gets a hint, and after a third miss the beads set themselves to the answer. Five right first time in a row suggests the next level; moving up is always your choice.

The beads and practice progress are saved on this device only, for each player. Clear and Reset progress both offer Undo. Sound is off until you turn it on.