A new species of monkey found in the Democratic Republic of the Congo and identified as Lesula (Cercopithecus lomamiensis) is seen in this undated photograph from an article published September 12, 2012 in the science journal PLOS One. The monkey was first seen in 2007 by researchers John and Terese Hart of the Peabody Museum of Natural History at Yale Research Project. The finding of C. lomamiensis represents only the second new species of African monkey to be discovered in the past 28 years, according to the research article. (Photo by Hart J. A., Detwiler K. M., Gilbert C. C./Reuters)

Michael Read, director of Flight Operations from New Zealand-based Martin Aircraft Company, flies a Martin Jetpack during a demonstration at a water park in Shenzhen, China December 6, 2015. KuangChi Science Ltd, a Hong Kong-listed Chinese company and investor of Martin Aircraft, will sell the flying machine in mainland China for 1.6 million yuan ($249,902), according to the company. (Photo by Bobby Yip/Reuters)

Members of a Star Wars fan club wear costumes of movie characters as they join a midnight premiere of the new Star Wars movie “Star Wars: The Force Awakens” at a cinema in Stuttgart, Germany, late 16 December 2015 night. Numerous fans of the science fiction movie series were gathering to attend one of the midnight premiere screenings all over Germany of the latest movie of the epic series – “Star Wars: The Force Awakens”. (Photo by Nikolai Huland/EPA)

Chinese workers maintain an Animatronic Dinosaurs at Gengu Dinosaurs Science and Technology company on November 13, 2019 in Zigong, Sichuan Province, China. There are hundreds of simulated dinosaur manufacturers in Zigong City. It is the largest simulated dinosaur manufacturing in China. It accounts for 95% of mainland China's production and 85% of the world's total. Its products are exported to more than 100 countries. (Photo by Lintao Zhang/Getty Images)

Yogis and street performers have been simulating levitation with nifty contraptions forever. They appear to be held aloft via nothing but their preternatural mental prowess. But are really enjoying the benefits of basic physics just like the rest of us when we use a chair. However, just because it’s perfectly explainable doesn’t mean it isn’t nifty. I’m especially impressed by this 2-person version and am still trying to work out how exactly the chair they’re using is shaped at the base.

A young man, who says he is part of a local criminal gang, poses for a picture holding a gun in the neighbourhood of Korogcho in Nairobi, Kenya, March 19, 2015. Around 2 million people live in the shantytowns packed in around Kenya's capital. Crime is high amid chronic unemployment levels, while basic services and sanitation are scarce. Residents try to make the best of things, eking out a living and picking up work where they can. (Photo by Siegfried Modola/Reuters)

Urszula Sidoruk, 19, from the paramilitary group SJS Strzelec (Shooters Association), trains her workout at a gym in Siedlce, eastern Poland March 18, 2014. Inspired by the war in Ukraine, growing numbers of Poles are joining volunteer paramilitary groups, where they receive basic army training and prepare to defend their homeland. (Photo by Kacper Pempel/Reuters)

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.