Six lines, three triangles or one square?
function setup() {
var canvas = createCanvas(500, 500);
canvas.parent('sketch');
colorMode(HSB);
background(98);
stroke(15);
strokeWeight(2);
noFill();
rectMode(CENTER);
rect(width / 2, height / 2, width / 3, height / 3);
line(width / 3, 2 * height / 3, 2 * width / 3, height / 3);
line(width / 3, width / 3, width / 2, height / 2);
}