This seems to be a faithful computer adaptation of Puyo Puyo. I haven't played it, but I heard that it's good. The author's
description is:

PuyoPuyo 1.0 - PuyoPuyo a fast, fun and addicting action game. Match up four same-colored Puyos that touch and they disappear. They don't need to line up, they just have to touch (but it doesn't work diagonally). PuyoPuyo features 8-bit, fully animated color graphics and excellent music. You can play solo, against a computer opponent or another person to try to keep your Puyos from stacking up the top of the grid. Try it, it's fun. Shareware.

Puyo Puyo for Macintosh can be downloaded at ftp://ftp.amug.org/pub/amug/bbs-in-a-box/files/game/n-q/puyopuyo-1.0.sit.hqx or ftp://sunsite.cnlab-switch.ch/mirror/amug/files/game/n-q/puyopuyo-1.0.sit.hqx

Graphic and description from Ranma^-^