/*https://editor.p5js.org/p5/sketches/Structure:_No_Loop
 * @name No Loop
 * @description The noLoop() function causes draw() to only execute once.
 * Without calling noLoop(), the code inside draw() is run continually.
 */
let y;

// The statements in the setup() function
// execute once when the program begins
function setup() {
  // createCanvas should be the first statement
  createCanvas(720, 400);
  stroke(255); // Set line drawing color to white
  noLoop();

  y = height * 0.5;
}

// The statements in draw() are executed until the
// program is stopped. Each statement is executed in
// sequence and after the last line is read, the first
// line is executed again.
function draw() {
  background(0); // Set the background to black
  y = y - 1;
  if (y < 0) {
    y = height;
  }
  line(0, y, width, y);
}