var ball_num;

var ballX = [];

var ballY = [];

var speedX = [];

var speedY = [];

var ball_color = [];

var ball_diameter = [];



var colors = [];



function setup() {

  createCanvas(windowWidth,

               windowHeight);



  ball_num = 800;

 colors.push(color(150, 150, 150));

  colors.push(color(128, 192, 255));

  colors.push(color(64, 160, 255));

  colors.push(color(255, 192, 128));

  colors.push(color(255, 128, 0));



  for (var i = 0; i < ball_num; i = i + 1) {

    ballX[i] = random(0, windowWidth);

    ballY[i] = random(0, windowHeight);

    speedX[i] = random(-2.0, 4.0);

    speedY[i] = random(-2.0, 4.0);

    ball_color[i] = floor(random(0, colors.length));

    ball_diameter[i] = random(8, 20);

  }

}



function draw() {

  background(255, 255, 255, 100);

  noStroke();



  for (var i = 0; i < ball_num; i++) {

    ballX[i] = ballX[i] + speedX[i];

    ballY[i] = ballY[i] + speedY[i];



    if (ballX[i] > windowWidth || ballX[i] < 0) {

      speedX[i] = -1 * speedX[i];

    }



    if (ballY[i] > windowHeight || ballY[i] < 0) {

      speedY[i] = -1 * speedY[i];

    }

  }



  for (var i = 0; i < ball_num; i++) {

    fill(colors[ball_color[i]]);

    ellipse(ballX[i], ballY[i], ball_diameter[i]);

  }



}