The Aletsch Glacier is pictured at dusk in Fiesch, Switzerland, August 11, 2015. One of Europe's biggest glaciers, the Great Aletsch coils 23 km (14 miles) through the Swiss Alps – and yet this mighty river of ice could almost vanish in the lifetimes of people born today because of climate change. The glacier, 900 metres (2,950 feet) thick at one point, has retreated about 3 km (1.9 miles) since 1870 and that pace is quickening. (Photo by Denis Balibouse/Reuters)

A cosplayer dressed as Batman wearing the Hellbat suit crosses the road during Day 1 of New York Comic Con at Javits Center on October 07, 2021 in New York City. Comic Con has returned this year after being cancelled in 2020 due to the coronavirus pandemic. (Photo by Alexi Rosenfeld/Getty Images)

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.

Thousands of heavy-duty trucks loaded with coal are lined up for up to 130 kilometres from the Mongolia-China border on a sole road in the Gobi desert, Mongolia, October 29, 2017. The journey can take more than a week. (Photo by Bazarsukh Rentsendorj/Reuters)

A Student of Yuba Pratibha School, wearing a face shield and masks at school during a coronavirus pandemic in Kathmandu, Nepal, 26 November 2020. The head Teacher of Yuba Pratibha School, Yanga Raj Dahal, started to conduct classes for students, who can’t afford and attend online classes, with strict sanitary regime, providing also free face masks and shields for students. However majority of schools have been conducting online classes in Nepal from 19 March 2020 as part of precautionary measures against the spread of the coronavirus Covid-19. (Photo by Narendra Shrestha/EPA/EFE)

Performers dressed as Pikachu, the popular animation Pokemon series character, perform in the Pikachu parade in Yokohama on August 7, 2016. Some 50 life-size Pikachu characters, the most famous from the Pokemon game, marched along the city’s waterfront street as visitors took mobile phone pictures and videos of them in scorching sunshine. Some participants said they attended the event to search for rare characters of Pokemon – a word short for “pocket monster” – for the megahit smartphone app, which was launched in several countries around the world last month. (Photo by Kazuhiro Nogi/AFP Photo)

Jeremy Davis (L) demonstrates the operation of the safe room shelter door lock to homeowner Rob Hamlin on June 18, 2011 in Neosho, Missouri. Once thought of as a luxury item there has been a surge of interest from homeowners in purchasing shelters to ride out damaging storms ever since a F5 tornado tore through the town of Joplin, Missouri. Ranging in price from $3,000 to $5,000 homeowners can supplement the cost with a mortgage insurance program offered by the U.S. Department of Housing and Urban Development for installing a safe room built to FEMA specifications. Lawmakers in Alabama have even considered requiring construction of storm shelters in mobile home parks after forty people died in April. (Photo by Julie Denesha/Getty Images)

“Himalayan Dog”. This dog just appeared out of nowhere and followed us for an entire week during our trekking trip in the Himalayan outback. He always used to sleep in front of our tent and guarded us in the nights. When I decided to get up at 4 a.m. to climb the next 5000 m peak for sunrise he accompanied me as well. On the top he was sitting for the entire 30 minutes on this place looking straight into the countryside. Photo location: Ladakh, India. (Photo and caption by Sebastian Wahlhuetter/National Geographic Photo Contest)