Play against the computer – Connect Four game in JavaScript
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Basically when it’s the computer’s turn it evaluates every possible move and assigns an attack and defense value for each move. The attack value is based on how many in a row and whether it can win on next turn, and the defense value is how many opponent’s chips in a row and whether it will lose on opponent’s turn. And if 2 or more moves are equal, favor the move closest to the center of the board.
A strategy that works for me is building a tower. In that tower try to construct 2 rows of 3 length, can be one horizontal and one diagonal but doesn't have to be, that when you go to one side of the tower, it would give you 4 in a row 2 times right after another circle is placed on top of the first one. While doing this also making sure the opponent isn't doing the same below your rows.
Doing this makes it impossible for the other to defend as when you're building on the side of the tower, it gives the opponent 2 options:
- Defending the first row and placing a circle, allowing you to place another on that circle and making the second 4 in a row.
- Or not defending and you can obviously finish your first in a row.
Following this strategy I was able to win both as player 1 and 2.
Basically when it’s the computer’s turn it evaluates every possible move and assigns an attack and defense value for each move. The attack value is based on how many in a row and whether it can win on next turn, and the defense value is how many opponent’s chips in a row and whether it will lose on opponent’s turn. And if 2 or more moves are equal, favor the move closest to the center of the board.
It's fairly difficult, but not perfect, and you can win as the second player.