​

let x = 0;

​

const SPD = 5;

​

const noiseScale = 0.01;

​

const distBetween = 20;

​

function setup() {

  createCanvas(400, 400);

}

​

function draw() {

  background(220);

  if(keys.a) x -= SPD;

  if(keys.d) x += SPD;

  if(x < 0) x = 0;

  let pos = (int(x/distBetween) - 1) * distBetween;

  beginShape();

  vertex(pos - x, height);

  while(pos < x + width + 2 * distBetween) {

    vertex(pos - x, terrainHeight(pos));

    pos += distBetween;

  }

  vertex(pos - x, height);

  endShape(CLOSE);

}

​

function keyPressed() {

  keys[key] = true;

}

​

function keyReleased() {

  delete keys[key];

}

​

function terrainHeight(x) {

  if(x < 0) x = 0;

  return height/2 + (noise(x * noiseScale) * (x / 20));

}