Tetra is a clone of the arcade smash Tetris. It is one of several games that Brian O'Neill released as shareware/freeware in the early 1990's for the Coco 3. Like the original arcade version, the object is drop different sized blocks in patterns to form solid horizontal lines, which will destroy that line, dropping everything above it down a level. You can move them side to side, and rotate them 90 degrees, while they are falling. This is one of the better freeware implementations.
Brian later went on to do one of the best commercial Coco 3 games: Pac Dude Monster Maze (3D Pacman, based on Pac Mania).
Title: Tetra
Author: Brian O'Neill
Publisher: Brian O'Neill
Released: 1991
Requires: Color Computer 3, 128K RAM, tape or disk.