Workshop › Tower Defense › Step 14 of 42

Click to build

What we are doing

You start with 120 gold. A click builds a tower of the selected kind on that tile and pays its cost. For now a click builds anywhere; the next step adds the rules.

```js
let gold

let selected // the kind of tower to build

  gold = 120

  selected = 'arrow'

function build(col, row) {
  const kind = TOWERS[selected]
  gold -= kind.cost
  towers.push({ col, row, kind: selected, cooldown: 0 })
}

canvas.addEventListener('pointerdown', (event) => {
  const p = tileAt(event)
  build(p.col, p.row)
})
```

What it means

build pays the kind's cost and adds { col, row, kind, cooldown }; cooldown will count the frames until the tower can shoot again.
pointerdown fires when a mouse button or a finger goes down on the canvas.

Your turn

Above let toSpawn write let gold; under let spawnIn write let selected.
In reset, above toSpawn = 30 write gold = 120, and at the end selected = 'arrow'.
Above function update() { write build and the pointerdown listener.

Skills: Keyboard and mouse input, Game states

← From a click to a tile Where can you build? →

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