Crystal Caves

"Crystal Caves is a shareware series of three side-scrolling platform games, developed and published by Apogee Software, released on 23 October 1991. The three episodes have the titles "Troubles with Twibbles," "Slugging it Out" and "Mylo Versus the Supernova."

The first episode is available for free, while the remaining two need to be paid for. According to the designer Frank Maddin, this marketing method "worked pretty well for the time." All three games have identical gameplay, and differ only in level design, some graphics and the story.

On October 24, 2005, 3D Realms (formerly Apogee) released a maintenance patch to fix a bug in the game which set the player's computer's clock backwards 100 years after playing on Windows XP. As the game was released 14 years and one day earlier, 3D Realms may now hold the record for longest time between an initial game release and a maintenance patch.

The player controls Mylo Steamwitz, a space trader who wants to invest in a number of get-rich-quick schemes. He travels to the Altairian star system and ventures into the caves in the planets there to harvest large, naturally grown crystals.

The objective of each game is to complete all 16 levels; there is no fixed order in which to play them."

Source: Wikipedia, Crystal Caves , available under the CC-BY-SA License.