gistfile1.pde

int retweet_number = 20;
int base_size = 20;

void setup() {
  size(800, 800);
  background(0, 0, 0);
  smooth();
};

void draw() {
  background(0, 0, 0);
  
  for (int i = 1; i <= retweet_number; i = i + 1) {
    int increment = 100 / retweet_number;
    int alpha = increment * (retweet_number - i);
    
    if (i == 1) {
      fill(#FFFFFF);
    }
    else {
      noFill();
    }
    
    stroke(255, 255, 255, alpha);
    strokeWeight(20);
    ellipse(width / 2, height / 2, base_size * i, base_size * i);
  }
};