Crystal Caves 1: Troubles with Twibbles

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.

Mylo Steamwitz has to get all the crystals in each screen ('cave') to win that screen, but this requires shooting foes (with the need to replenish ammo), avoid shooting air supplies, find & turn on the lights, and turn switches on or off. Though mostly straight shoot-em-up, the game does involve some careful problem solving, with the risk of mistakes that make completing the cave impossible. He enters and leaves caves by doors to individual rooms from a central cavern, which doors function in-game as teleportation booths.