Gem Drop X is an interesting one-player puzzle game for X-Window.

  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!))

  The game is played  with YOU at the bottom of the screen.  At the
top is a random assortment of colored shapes ("gems"). As time goes
on, more  gems  appear at the very  top of the  screen, pushing the
rest downwards.  The game is over when the gems reach the bottom.

WWW: http://www.newbreedsoftware.com/gemdropx/