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)

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)

Construction cranes stand on the Unstrut Valley high-speed railway bridge on March 19, 2012 near Karsdorf, Germany. The Unstrut bridge, which is 2,668m long (about 1.6 miles), is among 38 bridges and 26 tunnels German state rail carrier Deutsche Bahn is building along a new ICE high-speed railroad connection between Nuremberg, Erfurt, Halle, Leipzig and Berlin in a multi-billion Euro project across eastern Germany called the German Unity Transportation Project (Verkehrsprojekt der Deutschen Einheit). (Photo by Sean Gallup/Getty Images)

Amateur Iranian photographer Mohammad Reza Domiri Ganji, 23 likes to learn as much as he can about a site before he photographs it. Then he utilizes a variety of wide-angle and fisheye lenses, as well as occasional panoramic techniques to create beautiful new, often mind-bending images. He usually shoots the architectural wonders of Iran, and hopes that the Iranian government will allow him to travel further from home in pursuit of other iconic architectural treasures. Photo: The Nasir al-mulk or “Pink” mosque in Shiraz, Iran. (Photo by Mohammad Reza Domiri Ganj)

A bench engraved with the name of the grounded Costa Concordia cruise ship (seen at rear) is seen washed up on the shore of Giglio island, in this January 20, 2012 file photo. The trial of Francesco Schettino, accused of causing the deaths of 32 people in the 2012 Costa Concordia cruise ship disaster, nears its climax with a verdict expected over the coming days. The prosecution has demanded that he be jailed for 26 years but the captain denies all the charges against him. Schettino was the commander of the vessel when it came too close to shore and hit rocks off the Tuscan holiday island of Giglio. (Photo by Paul Hanna/Reuters)

A picture of Moon Ji-sung, a high school student who died in the Sewol ferry disaster, hangs in her room in Ansan April 7, 2015. Her dream was to be a flight attendant. Nearly a year after the Sewol ferry sank on April 16, 2014, with the death of 250 students, some families keep their children’s bedrooms intact to remember and honour their loved ones. More than 300 people, most of them students and teachers from Danwon High School, are dead, or missing and presumed dead, after the Sewol ferry sank on a routine trip from the port of Incheon, near Seoul, to the holiday island of Jeju. (Photo by Kim Hong-Ji/Reuters)

The Longsheng Rice Terraces are located in Longsheng County, about 100 km (2 hours drive) from Guilin, Guangxi, China. The most popular are Ping An Rice Terrace and Jinkeng Rice Terrace. The terraced fields are built along the slope winding from the riverside up to the mountain top, the highest part being 880 m in elevation while the lowest part is 380 m[citation needed]. The coiling line that starts from the mountain foot up to the mountain top divides the mountain into layers of water glittering in the sun in spring, layers of green rice shoots in summer, layers of golden rice in fall, and layers of silvery frost in winter. The terraced fields were mostly built during the Ming Dynasty, about 500 years ago.