A small board with deep roots
Four in a Row is a gravity game. Discs fall to the lowest open slot, so you never choose a row, only a column. On this 6 by 7 grid you can't play wherever you like. You can only play where the stack has reached, and much of the strategy is about which slots become reachable, and when.
The game has been fully solved by computer. With perfect play the player who moves first can force a win by starting in the middle column. The solution still points at what matters most: the middle column, and who fills the last useful slots.
Count lines, not discs
A disc is only worth the lines of four it can still join. A disc in the middle column can join lines across, down and both diagonals, and it sits inside the most of them. A disc on the outer edge joins far fewer. Early on, prefer the middle three columns and stack them while they're open.
- Open with the middle column when you move first. If the computer goes first and takes it, answer next to it or on top of it.
- Build shapes that point two ways. Two discs side by side low on the board threaten a line across. A third disc above one of them adds a diagonal.
- Leave the outer columns for later. They fill with discs that block more than they build.
Odd rows, even rows
Number the rows 1 to 6 from the bottom. Late in the game, when most columns are full, players are often forced to drop discs they don't want to drop. Whoever moved first tends to end up filling the odd rows, and whoever moved second the even rows. So a threat sitting on an odd row usually helps the first player. A threat on an even row usually helps the second.
Here is how that plays out. Say you moved first and have three red discs on row 3, with the gap in column 6. Column 6 is filled only up to row 1. Neither side wants to play there now. If the computer drops into column 6, its disc lands on row 2 and you win on row 3. If you drop there, your disc lands on row 2 and the computer blocks on row 3. So both of you avoid that column. As the other columns fill, someone has to give way, and the row count decides who. A threat like that is worth more than an extra disc in the middle.
Mistakes the board punishes
- Playing under your opponent's threat. Before every move, look at the slot directly above where your disc will land. If the computer has three in a line waiting on that slot, your move hands it the win.
- Missing diagonals. Diagonal lines climb across columns at different heights, and they're the ones that catch you. Scan both diagonal directions from the computer's last disc.
- Blocking only the obvious threat. When the computer has two separate ways to win, blocking one loses to the other. The fix is earlier: stop a line at two discs, not three, when it has room at both ends.
- Rushing for a win you can't finish. Three in a row with no reachable fourth slot is not a threat yet. Ask whether the stack can get there, and who will be forced to fill below it.
A way to practise
Start on Easy. Its search is shallow and it sometimes plays at random, so you can test ideas like stacking the middle or setting up an odd-row threat and see them work. Medium looks four moves ahead and will punish a careless move under a threat. Use it to make the slot-above check a habit. Hard searches much deeper in a short time budget and rarely leaves a tactic on the table. Against it, focus on long-term play: the middle column, threats on your rows, and making the computer run out of safe moves.
Try both settings for who goes first. Moving first gives you the middle column and the odd rows. Moving second teaches you to defend and to look for even-row threats instead. If you enjoy reading lines and threats, Five in a Row plays on the same ideas, without gravity and on a far bigger board.
