only straight lines

let w;
let ptOld;
let pt;
let t = 0;
let curves = 0;
function setup() {
  cnv = createCanvas(windowWidth, windowHeight);
  background(235);
  strokeWeight(0.5);
  stroke(0, 0, 0, 20);
  ptOld = { x: mouseX, y: mouseY };
  pt = { x: mouseX - 1, y: mouseY - 1 };
}

function draw() {
  t += random(0.008, 0.012);
  defPoint();
  if (pt.x - ptOld.x != 0) {
    m = (pt.y - ptOld.y) / (pt.x - ptOld.x);
  } else {
    m = (pt.y - ptOld.y) / (pt.x - ptOld.x + 0.0001);
  }
  x1 = 0;
  y1 = m * (x1 - pt.x) + pt.y;
  x2 = width;
  y2 = m * (x2 - pt.x) + pt.y;
  if (abs(m) > 0 && abs(m) < 10000 && t > 0.12) {
    line(x1, y1, x2, y2);
  }
  ptOld = { x: pt.x, y: pt.y };
}

function defPoint() {
  if (curves === 0) {
    pt = { x: mouseX, y: mouseY };
  } else if (curves === 1) {
    r = min(width, height) / 3;
    pt = { x: width / 2 + r * cos(t), y: height / 2 + r * sin(t) };
  } else if (curves === 2) {
    r = min(width, height) / 3;
    pt = { x: int(t * 100) % width, y: height / 2 + r * sin(t) };
  } else if (curves === 3) {
    r = min(width, height) / 3;
    pt = { x: width / 2 + r * sin(t) * cos(t), y: height / 2 + r * sin(t) };
  } else if (curves === 4) {
    r = min(width, height) / 3;
    pt = {
      x: width / 2 + r * sin(t) * cos(t),
      y: height / 2 + r * sin(t) * sin(t / 2)
    };
  } else if (curves === 5) {
    r = min(width, height) / 3;
    pt = {
      x: width / 2 + r * sin(t) * cos(t / 3) * sin(t / 4),
      y: height / 2 + r * sin(t) * sin(t / 2)
    };
  } else if (curves === 6) {
    r = min(width, height) / 3;
    pt = {
      x: width / 2 + r * sin(t) * cos(t / 3) * sin(t / 4),
      y: height / 2 + r * sin(t / 3) * cos(t / 2)
    };
  } else if (curves === 7) {
    r = int(t * 100) % int(width / 2);
    pt = { x: width / 2 + r * sin(t), y: height / 2 + r * cos(t) };
  } else if (curves === 8) {
    r = (int(t * 100) % int(width * 4)) / 10;
    pt = { x: width / 2 + r * sin(t), y: height / 2 + r * cos(t) };
  } else if (curves === 9) {
    r = min(width, height) / 3;
    rand = random(0, 2 * PI);
    pt = { x: width / 2 + r * sin(rand), y: height / 2 + r * cos(rand) };
  }
}
function keyPressed() {
  if (keyCode === 32) {
    background(235);
  }
  if (keyCode === 83) {
    save(cnv, "lines", "png");
  }
}

function mousePressed() {
  background(235);
  curves = (curves + 1) % 10;
  t = 0;
}