Piet Hein, who, in his own words, "played mental ping-pong" with Niels Bohr in the inter-War period, found himself confronted with a dilemma when the Germans occupied Denmark. He felt that he had three choices: Do nothing, flee to "neutral" Sweden or join the Danish resistance movement. As he explained in 1968, "Sweden was out because I am not Swedish, but Danish. I could not remain at home because, if I had, every knock at the door would have sent shivers up my spine. So, I joined the Resistance."
Taking as his first weapon the instrument with which he was most familiar, the pen, he wrote and had published his first "grook" [gruk in Danish]. It passed the censors who did not grasp its real meaning.
CONSOLATION GROOKLosing one gloveis certainly painful,but nothingcompared to the pain,of losing one,throwing away the other,and findingthe first one again.
The Danes, however, understood its importance and soon it was found as graffiti all around the country. The deeper meaning of the grook was that even if you lose your freedom ("losing one glove"), do not lose your patriotism and self-respect by collaborating with the Nazis ("throwing away the other"), because that sense of having betrayed your country will be more painful when freedom has been found again someday. Denmark got the message.
After Liberation, Scandinavian architects, tired of square buildings but cognizant that circular buildings were impractical, asked Piet Hein for a solution. Applying his mathematical prowess to the problem, Piet Hein created the superellipse which became the hallmark of modern Scandinavian architecture.
In addition to the thousands of grooks he wrote, Piet Hein devised the games of Hex, Tangloids, Morra, Tower, Polytaire, TacTix, Nimbi, Qrazy Qube, Pyramystery, and the Soma cube. He advocated the use of the superellipse curve in city planning, furniture making and other realms. He also invented a perpetual calendar called the Astro Calendar and marketed houseware based on the superellipse and Superegg.