Games can be found in all kinds of places, from the living room on consoles to retro-themed bars in arcade cabinets, and sometimes even lurking inside other games.
Some games are to players what dreams are to the characters in Inception - merely the first level of a pyramid comprising more than one plane of virtual existence.
These occasionally take the form of mini-games so different from the core title that they could have been given a standalone release. At other times retro classics from yesteryear have been planted inside modern titles as Easter eggs, unlockable bonuses or a nostalgic distraction from the main event.
This is a trend which dates back across the generations, and it took on a new level of prevalence as hardware grew more sophisticated. By the time the PlayStation era came around, Ridge Racer enthusiasts were playing Galaxian on the loading screen and Chocobo Racing was given a standalone release after debuting as a fan-favourite minigame in Final Fantasy VII.
Although games within games have been delighting fans for decades, this trend is going nowhere, since there are examples of it cropping up on PS4 and Xbox One.
10. Maniac Mansion (Day Of The Tentacle)
Point-and-click purveyors LucasArts did something unprecedented in 1993: they released a sequel with its predecessor hidden inside, a game within a game, entirely free to play.
Day of the Tentacle could be enjoyed as a standalone story, but those curious about the events which led up to its time-jumping hijinx only had to visit the Edison family motel's security office and click on the computer in the corner.
Suddenly the graphics and sound quality took a nose and the nostalgia was cranked up to 11 as players were thrust head first into the previous game, Maniac Mansion. The entire adventure could be experienced within Day of the Tentacle, unaltered from the version that hit the Commodore 64 and Apple II in 1987.
Day of the Tentacle was remastered and reissued for modern platforms in 2016 and, although Maniac Mansion didn't get the same treatment, the previous game still came bundled with its polished-up sequel as an Easter egg.