SOURCE

/* 随机游走 */
var w;

function setup(){
  createCanvas(600, 400);
  w = new Walker();
  background(0)
}
function draw(){
  w.step()
  w.render()
}

class Walker{
  constructor(){
    this.x = width / 2;
    this.y = height / 2;
  }
  step(){
    var choice =random(1);
    if(choice < 0.4){
      this.x++
    } else if (choice < 0.6){
      this.x--
    }else if (choice < 0.8){
      this.y++
    }else{
      this.y--
    }

    // constrain(n,low,high) 应该是压制在canvas内

    this.x = constrain(this.x, 0, width-1);
    this.y = constrain(this.y, 0, height-1);
  }
  render(){
    stroke(255)
    point(this.x, this.y)
    // ellipse(this.x, this.y,20)
  }
}