There is a stack with four digits. There are seven buttons: add mul sub mod div rot swp You have a mission. Make the number 24. Example stack is [ 1 3 4 2 ] add => [ 1 3 6 ] mul => [ 1 3 8 ] sub => [ 1 3 2 ] mod => [ 1 3 0 ] div => [ 1 3 2 ] rot => [ 1 4 2 3 ] swp => [ 1 3 2 4 ] Example solution: mul mul => [ 1 24 ] If you press any extra button you lose levels, big time, OMG.
The solutions to 5931 problems was found with Ruby in two minutes. Hardest problem takes eight button clicks. Credits to Slava Pestov, inventor of Factor. Music by the fabulous RetroPancake.