Earth Treasure

Earth Treasure is a pocket soroban dojo for family math circles, Japanese-school students, and adults returning to mental math. You put the answer on a brass reckoning bar with few bead moves. A calculator keypad is never the main act, and there is no worksheet journal. Thirteen rods sit on the frame, each with one heavenly bead and four earth beads. Beads snap to the reckoning bar with haptic ticks. While you work, a place-value lantern lights the active rod from ones through billions. The seeded dojo includes 48 problems across addition, subtraction, and two-digit multiplication, with 5-companion and 10-companion coaching. Hint chips name which beads to raise or drop without moving them for you. When you want the economical path, expert replay animates a bead-accurate solution you can step through rod by rod. Hidden-bead ank flash shows the frame for 1.5 seconds, then covers it. You commit the number on a keypad used only for that drill. A session recap card reports correctness, extra bead moves versus the expert, and which companions you invoked. Study the technique library of eight illustrated cards: clear frame, simple add, add with 5-companion, subtract with 10-companion, multiplication setup, division intro, decimal-point rod, and mental picture. A glance widget and a morning warm-up of eight seeded problems arrive through local notifications, with no account required. Large beads, high contrast, and spoken rod names support accessible practice. The app remembers handedness and reduced-motion preferences on device.