Gem Drop X is an interesting one-player puzzle game for X-Window.
  It's been written in C under Unix and requires you to compile the
  source code to produce the executable program itself.  You'll also
  of course need an X display terminal or software to actually see
  the game.  (Although a curses version may be released at one point!)

  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!))