A sun bear reacts to triple-digit temperatures at the Henry Doorly Zoo in Omaha, Nebraska, where the temperature reached 103 degrees Fahrenheit on July 6, 2012. (Photo by Nati Harnik/Associated Press)

“Spare bits = spare bots. Time on hands + obsession with uselessness = make trivial things. Made from capacitors, diodes, resistors, leds, bits of wire, solder, and time...” – Lenny & Meriel. Photo: “9V tragedy”. (Photo by Lenny&Meriel)

A woman wearing cut-off jeans and a halter-neck sun top in St Tropez, 1972. (Photo by Roy Jones)

A man looks inside an overturned truck after an accident along the road between Nouahibou and Nouakchott, Mauritania December 3, 2009. (Photo by Rafael Marchante/Reuters)

A woman takes a photo of a mural by Berlin-based street artist Eme Freethinker featuring the likeness of US actor Will Smith (R) slapping US comedian Chris Rock during the Oscars ceremony, in Berlin on March 30, 2022. (Photo by John MacDougall/AFP Photo)

Aerial photo taken on April 10, 2022 shows the construction site of Haikou duty-free shopping complex in Haikou, south China's Hainan Province. With a total construction area of about 926,000 square meters, the Haikou duty-free shopping complex project is expected to be officially put into use this year. (Photo by Xinhua News Agency/Rex Features/Shutterstock)

Public Space series, 2015. This series by Morteza Niknahad and Behnam Zakeri tends toward cinema, taking an almost cartoonish view of modern life in Iran. This work was inspired by the social life of dolphins. (Photo by Morteza Niknahad and Behnam Zakeri/The Guardian)

Everyone wants to get something for nothing - whether it's a lucky upgrade that means you can turn left when you get on a plane instead or heading off into the economy seats, or even getting a few extra features thrown in for free when you buy a new car.

As some of the sharpest businesses around, no-one understands this quite as well as casinos and that's why they all have a system that they call comps. It's short for "complimentary offers" and these are special treats specially designed to reward you for your loyalty to the casino in question. They're basically bonuses.