Wikipedia
Welltris
Welltris is a puzzle video game, developed by and licensed to Bullet-Proof Software. Adaptations were made by Sphere, Inc for Spectrum Holobyte, and by Infogrames. It was originally released for DOS and Macintosh in 1989. It was subsequently ported to the Amiga, Amstrad CPC and Atari ST in 1990 and the ZX Spectrum and Commodore 64 in 1991.