1. Four Corners

(Shows positioning + simple shapes)

function setup() {
  createCanvas(300, 300);
  background(240);

  fill(255, 0, 0);   circle(50, 50, 60);
  fill(0, 255, 0);   circle(250, 50, 60);
  fill(0, 0, 255);   circle(50, 250, 60);
  fill(255, 200, 0); circle(250, 250, 60);
}

2. Three Rectangles

(Pure minimal color-block composition)

function setup() {
  createCanvas(300, 300);
  background(255);

  fill(200, 50, 50);   rect(20, 20, 260, 80);
  fill(50, 120, 200);  rect(20, 120, 260, 80);
  fill(250, 200, 0);   rect(20, 220, 260, 60);
}

3. Simple Cross

(Introduces line + strokeWeight)

function setup() {
  createCanvas(300, 300);
  background(255);

  stroke(0);
  strokeWeight(10);
  line(150, 40, 150, 260);
  line(40, 150, 260, 150);
}

4. Two Triangles

(Shows symmetry + triangles)

function setup() {
  createCanvas(300, 300);
  background(240);

  fill(100, 150, 255);
  triangle(50, 250, 150, 50, 250, 250);

  fill(255, 150, 100);
  triangle(80, 220, 150, 80, 220, 220);
}