The Devil's Calculator

An evil calculator has its normal arithmetic operators replaced with sadistically obscure functions. Using logic and algebraic puzzle solving, you must work backwards to interpolate them and purge the calculator of its demons.
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 along with several DLC levels, authored by famous mathematicians like Alex Bellos, Grant Sanderson, James Grime, Tony Padilla and James Tanton! The game was named a fan favorite of GDWC, and one of the top 10 indie games of 2019 by PAX.
Each level has you decipher the function of a mysterious operator and use it to calculate the number of the beast to progress. Advanced graphing mechanics, countless features and simple, yet innovative level design provide considerable depth to the gameplay. Players unlock the ability to create their own levels and play challenges others have created - including free DLC levels crafted by the game's creators, educators and mathematicians. With hand drawn artwork and a charming story, the Devil's Calculator is a genuinely fun and gratifying puzzle experience. The game was celebrated at the MOVES conference by the National Museum of Mathematics in New York City.
Cinq-Mars Media is a 501(c)(3) non-profit organization developing technology to support scientific research related to human safety and education, and to make such technology and research available on a charitable basis.