void draw_arrow(float x1, float y1, float x2, float y2, float offset, float weight, float distance_from_point) {
  if (x1 == x2 && y1 == y2) return;
  float angle = atan2(y2-y1, x2 - x1);
  float triangle_size = dist(x1, y1, x2, y2) / 50;
  pushMatrix();
  translate(x1, y1);
  PVector start = PVector.fromAngle(angle);
  start.setMag(distance_from_point/2 + offset/2 + weight/2);
  pushMatrix();
  translate(start.x, start.y);
  PVector v = PVector.fromAngle(angle);
  v.setMag(dist(x1, y1, x2, y2) - 2* (offset/2 + distance_from_point/2 + weight/2) - weight/2); 
  line(0, 0, v.x, v.y);
  pushMatrix();
  translate(v.x, v.y);
  rotate(angle);
  fill(255);
  triangle(-triangle_size * 2, - triangle_size, 0, 0, -triangle_size * 2, triangle_size);
  popMatrix();
  popMatrix();
  popMatrix();
}

void draw() {
  int edge_weight = 10;
  int point_weight = 30;
  int graph_weight = 2;
  if (frameCount % 60 == 0) {
    background(0);
    g.draw_graph(graph_weight, point_weight);
    g.draw_points(point_weight);
    stroke(#555555);
    if (!edges.isEmpty()) {
      int[] edge = edges.get(0);
      edges.remove(0);
      strokeWeight(edge_weight);
      draw_arrow(g.coords.get(edge[0]).get(0), g.coords.get(edge[0]).get(1), g.coords.get(edge[1]).get(0), g.coords.get(edge[1]).get(1), point_weight, edge_weight, 15);
    }
  }
}