The Devil's Calculator

An evil calculator has its normal arithmetic operators replaced with sadistically obscure functions. Using logic and a bit of algebra, you must work backwards to interpolate and use these corrupted operators to compute the 'number of the beast', 666, in order to purge the calculator of its demons and continue on. Non-profit and open-source, The Devil's Calculator is a highly original indie game that's as addicting as it is educational. Accessible to numberphiles and math novices alike, the first 20+ levels are 100% free to play and enjoy in the game's Demo.