Add up the Flashing Numbers - Test your Mental Math (Imaginary Abacus) Skills ! Features: - Extension Formulae to include/exclude - Number of Values to choose from - Number of Digits to choose from - Flash time (speed) can be changed from 2.0 to 0.4 seconds - Beep sounds on each flash (can be turned on/off) - Large sized Font on Black background for best visualization of numbers Please Rate and Share !