Spelunky

In the tutorial, the player starts off playing as Yang, who leaves a journal which is found by the next Spelunker, who is later confirmed in the second game to be known as Guy Spelunky. The aim of the game is to explore tunnels, gathering as much treasure as possible while avoiding traps and enemies. The spelunker can whip or jump on enemies to defeat them, pick up items that can be thrown to either attack enemies or set off traps, and use a limited supply of bombs and ropes to navigate the caves. Levels are randomly generated and grouped into four increasingly difficult "areas", each with a distinctive set of items, enemies, terrain types and special features.

Later areas contain more valuable treasures, secret locations, and items. If the player loses all their hearts or runs into an instant-kill trap, they will have to start from the beginning.

Spelunky was created by Derek Yu and released as freeware for Microsoft Windows on December 21, 2008. The source code of the Windows version was published under a software license permitting noncommercial distribution and modification on December 25, 2009. Based on this source code the game community created a community patch which added support for Mac OS X. Since the game source code became available community members have created many modified versions, or mods, of the original game.

Most of these were available via the forums on the website for Derek Yu's video game company, Mossmouth, where a list was maintained of finished mods. fyi" was created by the community to maintain a list of community-made content after the Mossmouth forums were shut down.

IGN gave the XBLA version a score of 9.0 and an Editor's Choice award, calling it "a superb 2D platformer that's as easy to hate as it is to love". GamesRadar gave the game 5/5, praising its gameplay and constant sense of discovery. GameTrailers gave the game a score of 8.3, praising its design but criticizing some control quirks and throwaway multiplayer. 1UP.com gave the game an A ranking, saying "it offers the same immediate, pick-up-and-play fun of Geometry Wars, but demands much more than the simple reflexive reactions of your lizard brain".

PC Gamer UK chose the remake of Spelunky as its 2013 game of the year. Eurogamer ranked Spelunky third on its Games of the Generation list. In 2015, Rock, Paper, Shotgun ranked the original Spelunky 1st on its The 50 Best Free Games On PC list. A difficult challenge run of Spelunky HD, known as an "eggplant run", was reported on by various video game news websites. In 2019, Spelunky was ranked 36th on The Guardian newspaper's The 50 Best Video Games of the 21st Century list.