Seven columns. Six deep.
The rules fit on a napkin. Drop a disc in a column and it falls to the lowest empty place. Four of one colour in a line wins at once: across, up, or along either diagonal. A full board with no four is a draw. Red always drops first.
Stand the frame up between two people and one of them sees it upside down. So here it lies on its side: the floor on the left, column numbers printed once for each end, and both of you reading it the same way. Your phone shows it upright, as it would stand on a kitchen table.