/* built with Studio Sketchpad: 
 *   https://sketchpad.cc
 * 
 * observe the evolution of this sketch: 
 *   https://p5js.sketchpad.cc/sp/pad/view/ro.8yUQ4vfyGEx/rev.1549
 * 
 * authors: 
 *   WolfeSVK
 *   Sketchpad Admin

 * license (unless otherwise specified): 
 *   creative commons attribution-share alike 3.0 license.
 *   https://creativecommons.org/licenses/by-sa/3.0/ 
 */ 



var pendulums;
var count
var ballSize;

var mass = 1;
var time = 0.1;
var grav = 9.8;
var anchor;
//var col;

function setup() {
  createCanvas(600, 400);

  pendulums = [];

  count = random(10,40);
  col = round(random(500-5*count));

  var lng = random(50,80);
  var ang = random(0*PI/180,180*PI/180);

  ballSize = (height - lng)/count;
  anchor = createVector(width / 2, 15);


for (var i=0; i<count;i++){
  pos = createVector(anchor.x+cos(ang)*lng, anchor.y+sin(ang)*lng);
  pendulums.push(new Ball(anchor.x, anchor.y, pos.x, pos.y, col+i*5));
  lng+=ballSize;
  }
}

function draw() {
  background(100);
  for (var i=pendulums.length-1;i>=0;i--){
  pendulums[i].update();
  pendulums[i].paint();
  }
}


function Ball(anchX, anchY, ballX, ballY, col) {

  this.col = col;
  this.anchorPos = createVector(anchX, anchY);
  this.ballPos = createVector(ballX, ballY);

  this.ball = p5.Vector.sub(this.ballPos, this.anchorPos);
  this.length = this.anchorPos.dist(this.ballPos);
  this.angle = atan2(this.ball.y, this.ball.x);
  this.angleVel = 0;
}

Ball.prototype.update = function() {
  this.ball = p5.Vector.sub(this.ballPos, this.anchorPos);
  this.angleAcc = -grav / this.length * sin(this.angle);
  this.angleVel += this.angleAcc * time;
  this.angle += this.angleVel;
  this.angle += HALF_PI; // set angle 0 to bottom
  this.ballPos.x = cos(this.angle) * this.length + this.anchorPos.x;
  this.ballPos.y = sin(this.angle) * this.length + this.anchorPos.y;
  this.angle -= HALF_PI; // restore
  this.ball = p5.Vector.sub(this.ballPos, this.anchorPos);

  this.col++;
  if (this.col > 499) this.col = 0;

}

Ball.prototype.paint = function() {


  push();
  colorMode(HSB, 500, 100, 100);
  
  stroke(this.col, 100, 40);
  fill(this.col, 100, 40);
  line(this.anchorPos.x, this.anchorPos.y, this.ballPos.x, this.ballPos.y);


  ellipse(this.anchorPos.x, this.anchorPos.y, 5, 5);
  fill(this.col, 100, 100);

  ellipse(this.ballPos.x, this.ballPos.y, ballSize, ballSize);
  pop();
}

function keyPressed(){
  setup();
    }