Crystal Caves is a trilogy of 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.
Read more about Crystal Caves: Development, Game Play