mandala.pde

import java.util.*; 

void setup() {
  size(800, 600);
}

static final int OVAL_COUNT = 30;
static final int START_OPACITY = 255;

static final long SPAWN_DELAY = 250;
static final long DURATION = 1000;

List<Mandala> mandalas = new ArrayList<Mandala>();

long lastSpawnTime;

void draw() {
  background(14);
  noFill();
  
  long currentTime = System.currentTimeMillis();
  
  // Lägg till en mandala varje SPAWN_DELAY millisekunder
  if (currentTime - lastSpawnTime >= SPAWN_DELAY) {
    spawnMandala((int) random(50, width - 50), (int) random(50, height - 50));
    lastSpawnTime = currentTime;
  }
  
  Iterator<Mandala> iterator = mandalas.iterator();
  while (iterator.hasNext()) {
    Mandala mandala = iterator.next();
    
    pushMatrix();
    
    translate(mandala.x, mandala.y);
    stroke(mandala.shapeColor, mandala.opacity);
    
    float radToRotate = TWO_PI / OVAL_COUNT;
    for (int i = 0; i < OVAL_COUNT; i++) {
      rotate(radToRotate);
      ellipse(0, 0, mandala.shapeW, mandala.shapeH);
    }
    
    popMatrix();
    
    // Gör mandalan mindre opak beroende på hur länge mandalan funnits
    long timeSinceAddition = currentTime - mandala.addedTime;
    mandala.opacity = (int) (START_OPACITY - timeSinceAddition * START_OPACITY / (float) DURATION);
    
    // Ta bort mandalan om den är 100% transparent
    if (mandala.opacity <= 0) {
      iterator.remove();
    }
  }
}

void spawnMandala(int x, int y) {
  int h = round(random(150, 200));
  mandalas.add(new Mandala(x, y, 200 - h, h, generateRandomColor()));
}

// http://stackoverflow.com/a/43235/4313694
color generateRandomColor() {
  int r = round(random(0, 255));
  int g = round(random(0, 255));
  int b = round(random(0, 255));
  
  r = (r + 200) / 2;
  g = (g + 200) / 2;
  b = (b + 200) / 2;
  
  return color(r, g, b);
}

void keyPressed() {
  // Ta bort alla mandalas när man trycker på space
  if (keyCode == 32) {
    mandalas.clear();
  }
}

class Mandala {
  
  final int x;
  final int y;
  
  final int shapeW;
  final int shapeH;
  
  final color shapeColor;
  
  int opacity = START_OPACITY;
  
  final long addedTime = System.currentTimeMillis(); 
  
  Mandala(int x, int y,
          int shapeW, int shapeH,
          color shapeColor) {
    this.x = x;
    this.y = y;
    
    this.shapeW = shapeW;
    this.shapeH = shapeH;
    
    this.shapeColor = shapeColor;
  }
}

Very good!