//Create the ArrayList of Waves
ArrayList<Wave> waves = new ArrayList<Wave>();

void setup() {
  size(800, 800);

  //Set all ellipses to draw from the Center
  ellipseMode(CENTER);
  noFill();
  strokeWeight(2);
}

void draw() {
  //Clear the background with 21 opacity
  background(0, 0);

  if(frameCount%100 == 0){
      //Create a new Wave
    Wave w = new Wave();
    //and Add it to the ArrayList
    waves.add(w);
  }

  //Run through all the waves
  for(int i = 0; i < waves.size(); i ++) {
    //Run the Wave methods
    waves.get(i).update();
    waves.get(i).display();

    //Check to see if the current wave has gone all the way out
    if(waves.get(i).dead()) {
      //If so, delete it
      waves.remove(i);
    }
  }
}

//The Wave Class
class Wave {
  //Location
  PVector loc;
  //In case you are not familiar with PVectors, you can
  //think of it as a point; it holds an x and a y position

  //The distance from the wave origin
  int farOut;

  //Color
  color strokeColor;
  int strokeOpacity;

  Wave() {
    //Initialize the Location PVector
    loc = new PVector();

    //Set location to the Mouse Position
    loc.x = width/2;
    loc.y = height/2;

    //Set the distance out to 1
    farOut = 1;
   strokeOpacity = 255;


    //Randomize the Stroke Color
    strokeColor = color(255, strokeOpacity);
  }

  void update() {
    //Increase the distance out
    farOut += 1;

    if (farOut > 500){
    strokeOpacity--;
    }

  }

  void display() {
    //Set the Stroke Color
    stroke(255, strokeOpacity);

    //Draw the ellipse
    ellipse(loc.x, loc.y, farOut, farOut);
  }

  boolean dead() {
    //Check to see if this is all the way out
    if(farOut > 1500) {
      //If so, return true
      return true;
    }
    //If not, return false
    return false;
  }
}