|Colossal Cave Adventure|
There were text based games were released before it, such as Hunt the Wumpus, which was created in 1973. Hunt the Wumpus was known for its bats which would transport the player to another room, which also appear in Colossal Cave Adventure. However, Colossal Cave Adventure is considered the first adventure game, as it was the first game to have an inventory and puzzles, which remain a staple in most western adventure games to this day.
The cave in Colossal Cave Adventure is based on Bedquilt Cave, a cave within the Mammoth Cave system in Kentucky, that connects to Colossal Cave. In 1972, Will Crowther's wife Patricia was part of the team that found the link that connected Flint Ridge caves to the Mammoth Cave. The Bedquilt cave was Will's favorite part of the Mammoth cave system, so he decided to make a game based around it from a map he had made, in the hopes that it would be a game that his daughters would enjoy. As he was a fan of Dungeons and Dragons, he decided to combine elements of fantasy role-playing into the game as well. In the game, you search for treasure while navigating the maze-like caverns and avoiding or fighting the creatures.
The game had the elements that would become a staple of the genre, such as story based gameplay, puzzles, and inventory. It had a point-based system, where you're awarded an amount of points out of a possible total, based on whether you accomplished certain tasks in the game. This point system would be used in the games by the companies that were formed in which the founders were inspired by the game, such as Adventure International, Infocom, and Sierra. Sierra, in particular, continued the point system well into the graphical point-and-click era of adventure gaming.
This game was released for free, but some ports to other platforms and in other languages have been released commercially over the years. I have decided to put this game in the main section rather than the free games section because of it's importance. I usually list all the systems the games in the main section have been released on, but this game has been ported to just about every platform ever made. I'm not going to attempt to even try to list all the systems it's available on.