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From HF Innovations:
Ad supported version.The abacus app let's you count old school style. With a sophisticated device that can have any number of scientific calculators, why would you want an ancient abacus? Because you can. This is the ultimate abacus for the iPhone, iPod touch and iPad. Features: 8 columns of beads for iPhone and iPod touch 10 columns of beads for iPad 2 beads for upper section 5 beads for lower section Multitouch enabled - use more than one finger to push more than one bead at a time Move a single bead or multiple beads with a touch Flick beads with a quick motion Gravity/Acceleration enabled just tilt to move beads up or down or to reset Even responds to static and kinetic friction between rods and beads Real abacus 'click' sounds Wood grain textures for beads and frame Metal texture for rods