A Tetris/Columns clone for Amiga, created in 1989 by Avesoft's Signum Victoriae group, Tampere, Finland.
The idea of the game was simple enough: three-tile vertical colored blocks fall from the top of the screen, and the player must place them so that three or more tiles of same colors are on row - and when they are, they disappear.
Naturally, there was a Bigger Game Company that had also come up with this idea, and wasn't entirely happy of the fact they were being cloned - Avesoft wanted to publish this game outside Finland, but was afraid of the legal consequences. I guess the only end result from that legal battle is that I call these games "Coloris clones" instead of "Columns clones" =)
(Thanks to omegas for details!)