Drop discs into the columns and get four in a row, across, down or diagonally, before the computer does.
Three levels, and the hardest one will take any column you leave open.
Click a column to drop your disc into it. It falls to the lowest empty slot, which is the whole game in one sentence.
Four of your discs in a row wins, in any direction, including both diagonals.
Watch what your move hands over. Filling a slot often lets your opponent land on top of it, so the column you drop into matters as much as the row you are building.
The board is seven columns by six rows. If it fills with nobody connecting four, the game is a draw.
Yes, a lot. With perfect play the first player wins, and the winning first move is the middle column.
Diagonals are the hardest line to see, and they build underneath other threats. Check both diagonals through any slot before you fill it.
A move that creates two different ways to make four. Your opponent can only block one, which is how most games are actually won.
Easy plays mostly for itself, medium blocks your threats, and hard looks several moves ahead and sets up double threats of its own.
Connect Four was solved by computer in 1988: with perfect play the first player wins by starting in the middle column. That fact has not hurt it at all, because nobody plays perfectly.
The game is really about parity. Threats on the odd rows favour the first player and threats on the even rows favour the second, which is why strong players count rows before they drop.
If you want to improve quickly, stop blocking immediately and start asking what your block lets them do next.