Four in a Row

Most people learn this one as children and then find out how much deeper it goes. Two players take turns dropping discs into a seven-column, six-row grid; gravity does the rest, and the first to line up four in any direction wins.

You play against the computer at one of three strengths. Easy misses most setups but will still take a win or block one, medium looks four moves ahead, and hard looks six and is genuinely hard to beat. The opening move alternates between you and the computer each game, because going first is a real advantage in this game and it would be unfair to keep it.

You can also play another person. Open a table and you get a room code and a link; whoever you send it to sits down in the other seat, and neither of you needs an account. A bot takes the empty seat after fifteen seconds and gives it straight back when somebody arrives, so a table is never a dead end while you wait.

Tapping anywhere in a column drops your disc, so on a phone you aim at a whole column rather than at one small square. On a keyboard, the number keys one to seven do the same job. You always play gold, whichever seat you take. When somebody connects four, the winning line stays lit while the rest of the board fades, so the finish is easy to read at a glance. This browser remembers the strength you chose and how you have fared against it.