Workshop › Connect Four › Step 32 of 38

Prefer the middle

What we are doing

Rule 4: most lines of four pass through the middle columns, so they are the most useful. Each choice gets a score, higher closer to the middle, plus a little randomness so games differ, and the best score wins.

```js
// 4. Prefer the middle, where most lines of four pass; a little randomness breaks ties.
let best = choices[0]
let bestScore = -Infinity
for (const col of choices) {
  const score = -Math.abs(col - 3) + Math.random() * 0.5
  if (score > bestScore) {
    best = col
    bestScore = score
  }
}
return best
```

What it means

-Math.abs(col - 3) is 0 for the middle column and -1, -2, -3 towards the edges.
Math.random() * 0.5 adds up to 0.5, enough to pick between equal columns but never to beat a column nearer the middle.
The loop keeps the column with the highest score so far, starting from -Infinity, below every number.

Your turn

In computerMove, replace return choices[0] with the scoring lines.

Skills: Game states

← Don't help the player The computer's turn →

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