​

function setup() {

  createCanvas(400, 400);

  rectMode(CENTER);

}

​

function draw() {

  background(50);

​

  if (keyIsPressed) {

    if (key == "c") {

      // circle

      shapeMode = 0;

    } else if (key == "r") {

      // rect

      shapeMode = 1;

    } else if (key == "t") {

      // triangle

      shapeMode = 2;

    }

  }

​

  fill(255);

  noStroke();

  if (shapeMode == 0) {

    ellipse(mouseX, mouseY, 40, 40);

  } else if (shapeMode == 1) {

    rect(mouseX, mouseY, 40, 40);

  } else if (shapeMode == 2) {

    triangle(

      mouseX + 0,

      mouseY - 20,

      mouseX - 20,

      mouseY + 20,

      mouseX + 20,

      mouseY + 20

    );

  }

​

  text("Press c, r, or t!", 10, 20);

}

​