🖱️ Input

Read the mouse position, check if keys are pressed, and respond to user input. These let you make interactive programs and games!

mouseX

A variable that always holds the current X position of the mouse on the canvas.

Returns: number

function setup() {
  size(400, 200);
}

function draw() {
  background("white");
  fill("dodgerblue");
  noStroke();
  circle(mouseX, 100, 30);

  fill("black");
  textSize(14);
  text("mouseX: " + Math.round(mouseX), 10, 10);
}

mouseY

A variable that always holds the current Y position of the mouse on the canvas.

Returns: number

function setup() {
  size(400, 200);
}

function draw() {
  background("white");
  fill("tomato");
  noStroke();
  circle(200, mouseY, 30);

  fill("black");
  textSize(14);
  text("mouseY: " + Math.round(mouseY), 10, 10);
}

mouseIsPressed

A variable that is true when the mouse button is held down, and false when it's not.

Returns: boolean

function setup() {
  size(400, 200);
}

function draw() {
  if (mouseIsPressed) {
    background("tomato");
    fill("white");
  } else {
    background("white");
    fill("black");
  }
  textSize(24);
  text(mouseIsPressed ? "Pressed!" : "Click me!", 130, 85);
}

key

A variable that holds the most recently pressed key as a string, like "a", "Enter", or " " (space).

Returns: string

let lastKey = "(none yet)";

function setup() {
  size(400, 200);
}

function draw() {
  background("white");
  fill("black");
  textSize(24);
  text("Last key: " + lastKey, 80, 85);
}

function keyPressed() {
  lastKey = key;
}

keyIsPressed

A variable that is true when any key is held down, and false when no keys are pressed.

Returns: boolean

function setup() {
  size(400, 200);
}

function draw() {
  if (keyIsPressed) {
    background("mediumseagreen");
    fill("white");
  } else {
    background("white");
    fill("black");
  }
  textSize(20);
  text("Hold any key!", 120, 85);
}

keyIsDown(k)

Checks if a specific key is currently held down. Great for smooth game controls where you need to check multiple keys at once.

Parameter	Type	Description
`k`	`string`	The key to check, like "ArrowUp" or "a"

Returns: true if the key is held down, false if not

Tip: Common key names: "ArrowUp", "ArrowDown", "ArrowLeft", "ArrowRight", " " (space), "a", "w", "s", "d".

let x = 200, y = 100;

function setup() {
  size(400, 200);
}

function draw() {
  background("white");

  if (keyIsDown("ArrowLeft")) x -= 3;
  if (keyIsDown("ArrowRight")) x += 3;
  if (keyIsDown("ArrowUp")) y -= 3;
  if (keyIsDown("ArrowDown")) y += 3;

  fill("dodgerblue");
  noStroke();
  circle(x, y, 20);

  fill(150);
  textSize(12);
  text("Use arrow keys to move!", 120, 190);
}