From Sega Retro
Columns (コラムス) is a series of puzzle games owned by Sega after buying the rights to the original game from original developer Jay Geertsen. While initially somewhat successful, the series quickly stagnated under lack of innovation and competition from other arcade games and puzzle games — the original Columns and Columns II arrived during the shoot-'em-up craze and tried to fit in during the fighting craze, and in Japan, another puzzle game, Puyo Puyo Tsuu, proved far more popular. Nevertheless, Sega still pays attention to the series today, producing new titles on occasion (and never forgetting to put Columns in their myriad Sega Mega Drive game compilations).
Since all the games have the same fundamental gameplay, it is described here for convenience's sake.
The game area is a grid several columns wide. Three jewels in a column fall from the top of the screen. You can only rotate the jewels within the column — the column itself cannot be rotated. Once the jewels complete their descent, if three or more jewels of the same type form a line in any direction, they are cleared from the board. Occasionally, a Magic Jewel will fall. While the capabilities of the jewel vary from game to game, one capability will always be to make every jewel of the color of the jewel it touches disappear from the board. The game ends when any column — not just the column from which columns fall — overflows.
Starting with Columns III, when two players compete, the players build energy with each chain that allows them to attack the other player by sending nonremovable rows into the other player's well, rising the existing columns up. However, with countering energy (or in some cases a Magic Jewel), one can either reverse damage done to him or send that damage to to the other player. Columns III called the feature the "Crush Bar," however each successive game has given it a new name each time.