Gem Drop X is a direct port of Gem Drop, an Atari 8-bit game written in Action! (a very fast C- and Pascal-like compiled language for the Atari). The concept of the game Gem Drop is based directly on an arcade game for the NeoGeo system called "Magical Drop III" by SNK. If you're familiar with games like Jewels, Klax, Bust-A-Move or Tetris, this game is similar to them all. I consider it closest to Klax. (Jewels is like a combination of Klax and Tetris. Bust-A-Move is the least similar, in my opinion, but everyone seems to have heard of it more than the others (except Tetris, of course!))