Workshop › Pac-Man-style Maze Chase › Step 21 of 42

The ghost hunts you

What we are doing

The famous ghost brain is simple: of the allowed directions, take the one whose next tile is closest to a target, in a straight line. There is no path-finding: the ghost can take a wrong turn, and that is why you can outsmart it. For now the target is the player.

```js
function target(g) {
  return player
}

  const t = target(g)
  const distance = (d) => (g.col + d[0] - t.col) ** 2 + (g.row + d[1] - t.row) ** 2
  g.dir = options.reduce((bestDir, d) => (distance(d) < distance(bestDir) ? d : bestDir))
```

What it means

distance(d) is the squared straight-line distance from the next tile in direction d to the target. Squares are enough for comparing and avoid Math.sqrt. ** is "to the power of".
reduce walks the list keeping one "best so far": each option replaces it only if it is strictly closer, so ties go to the earlier one (up, left, down, right).

Your turn

Above chooseGhost, write target.
In chooseGhost, replace g.dir = options[0] with the three new lines.

Skills: Game states, Arrays and objects

← The ghost walks Four ghosts in the house →

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