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.

Kha Tu Ngoc rests in her two- square- meter house in Ho Chi Minh City on May 2, 2018. The “micro- house” dwellings are dotted throughout Vietnam' s bustling southern hub, occupied by families clinging to postage stamp- sized plots a city developing at breakneck pace. Tucked away in winding alleys, nestled under new condo developments or sandwiched between street food stalls and shops, the tiny houses are easily missed by the unattentive passerby. (Photo by Thanh Nguyen/AFP Photo)

An elephant calf yawns as mahouts paint elephants ahead of celebrations for the water festival of Songkran in Ayutthaya, Thailand on April 11, 2019. The annual elephant Songkran event is held to promote the tourism industry. Songkran Festival is held also to mark the Thai traditional New Year falling annually on 13 April, and it is celebrated with people splashing water and putting powder on each other faces as a symbolic sign of cleansing and washing away the sins from the past year. (Photo by Soe Zeya Tun/Reuters)

Some creations from the new “Funny Food Made Easy” book by Bill and Claire Wurtzel. “Inspiring kids to eat healthy foods with creative works of plate art and easy-to-follow instructions and illustrations. Through finished plate art, detailed step-by-step illustrations, recipes, and tips, Funny Food Made Easy provides all you and your kids need to make, eat, and enjoy healthy breakfasts, lunches, and snacks” – roughly speaking so. Here: Egg, cucumber, olive. (Photo by Bill and Claire Wurtzel/Welcome Books)

A view of Worker and Kolkhoz Woman, a sculpture by Vera Mukhina, at the main entrance to Moscow's VDNKh exhibition center in Moscow, Russia on September 27, 2017. (Photo by Dmitry Serebryakov/TASS/Barcroft Images)

People are seen in the crowd as Serbian Emir Kusturica & The No Smoking Orchestra performs during the third day of the Mexican musicial festival Vive Latino, at the Foro Sol in Mexico City, on March 29, 2014. (Photo by Alfredo Estrella/AFP Photo)

An Indonesian vendor fixes a headscarf on a mannequin at a market in Jakarta in this December 21, 2006 file photo. (Photo by Reuters/Beawiharta)

A polar bear whose bottom half is caked in oily black gunk. A whale wrapped in striped fabric: a pseudo straightjacket. These are the messes climate change leaves behind, the things we know are happening but often don’t have the opportunity to see with our own eyes. Swiss street art duo Christian Rebecchi and Pablo Togni, otherwise known as NeverCrew, met in art school when they were 15 and started making work together soon after. As a team, the artists adorn the world with eye-popping and gut-wrenching images depicting the consequences of humanity’s actions on earth. (Photo by NeverCrew/The Huffington Post)