In the early 1970s mathematician Donald Knuth spent a sabbatical with his wife in Norway. The time was meant to be spent relaxing. Yet one night he woke up his partner in a state of agitation. He ...

It’s the advanced algebra of optical illusions. Thought being in the top 1% of optical illusion buffs was impressive? Puzzle lovers are blowing a gasket trying to decipher this numerical eye exam, ...