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)

Children's author and charity fundraiser Chris Green, of Embsay, near Skipton, has been dubbed “Rhino Boy” as he has pledged to run 40 marathons and other events dressed as a Rhino to raise money for Save the Rhino on January 2020. (Photo by South West News Service/Yorkshire Post)

A girl reacts while getting a nasal swab sample at a testing and screening facility for the new coronavirus in a hospital in Karachi, Pakistan, Friday, July 17, 2020. (Photo by Fareed Khan/AP Photo)

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.

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)

Imagine living in the sea where it is permanently dark, cold, and food is hard to find. For many animals at depth, it may be weeks to months between meals. If you find something to eat, you have to hang on to it. This is why so many deep-sea fishes have lots of big teeth. This dragonfish, spotted off the coast of Australia, even has teeth on its tongue. They would be terrifying animals ... if they weren’t the size of a banana. (Photo by Julian Finn/Museum Victoria)

“The Dragon and The Hopper”. Eyrean earless dragon (Tympanocryptis tetraporophora) standing tall on a very hot rock in western Queensland. For a short time it was joined by a hopper, who jumped off before becoming lunch. (Photo by Harrison Warne/Nature Conservancy Australia 2021 Photo Contest)

Palestinians watch a man performs acrobatics on the beach of Gaza City, Friday, June 4, 2021. (Photo by Khalil Hamra/AP Photo)