Drop discs into the grid and race to line up four in a row before your opponent does.
Players alternate dropping colored discs into columns; each disc falls to the lowest open slot. Be the first to line up four of your discs in a row, horizontally, vertically or diagonally. Block your opponent's threats while building your own.
This is Connect Four, created by Howard Wexler and first sold under that trademark by Milton Bradley in February 1974. Drop a disc into a column, it falls to the lowest open slot, and four in a row wins.
The gravity rule is what separates it from ordinary noughts-and-crosses on a bigger grid: you choose a column, not a square, so the board decides half of every move.
It is also a solved game — the first player can always win with perfect play, by opening in the centre column. That has never hurt it, because the winning line is far too long for anyone to hold in their head, and the losing mistakes are the interesting part.
Dropline is an original take on the classic four-in-a-row line-drop game, with a sharp computer opponent plus local and online play. A free browser game made in-house at PlayPendium.