// initialize maxAccel (around 0.0025), maxRadSpeed (around 0.125), ballRadius (in pixels) and
// direction of acceleration (1 or -1)

StringBall sb_1 = new StringBall(0.0038, 0.19, 6, 1);
StringBall sb_2 = new StringBall(0.0026, 0.13, 9, -1);
StringBall sb_3 = new StringBall(0.0022, 0.11, 12, 1);
StringBall sb_4 = new StringBall(0.0018, 0.09, 15, -1);

 
 
void setup() 
{ 
  size(750, 750);
  //frameRate(36);
  noStroke(); 
  smooth();
} 

//public int count = 0;

void draw() 
{ background(255);
  sb_1.update(); 
  sb_2.update(); 
  sb_3.update();
  sb_4.update();
  //println( + sb_3.speedFactor + "  " + sb_3.stringLength);
  
  while (dist(sb_1.xpos, sb_1.ypos, sb_2.xpos, sb_2.ypos) <= (sb_1.ballRadius + sb_2.ballRadius) 
        && (sb_1.stringLength > 0.125 && sb_2.stringLength > 0.125)) 
  { sb_1.radSpeed *= -1; break;
  }
  while (dist(sb_1.xpos, sb_1.ypos, sb_3.xpos, sb_3.ypos) <= (sb_1.ballRadius + sb_3.ballRadius)
        && (sb_1.stringLength > 0.125 && sb_3.stringLength > 0.125)) 
  { sb_1.radSpeed *= -1; break;
  }
  while (dist(sb_2.xpos, sb_2.ypos, sb_3.xpos, sb_3.ypos) <= (sb_2.ballRadius + sb_3.ballRadius)
        && (sb_2.stringLength > 0.125 && sb_3.stringLength > 0.125))
  { sb_2.radSpeed *= -1; break;
  }
  while (dist(sb_1.xpos, sb_1.ypos, sb_4.xpos, sb_4.ypos) <= (sb_1.ballRadius + sb_4.ballRadius) 
        && (sb_1.stringLength > 0.125 && sb_4.stringLength > 0.125)) 
  { sb_4.radSpeed *= -1; break;
  }
  while (dist(sb_2.xpos, sb_2.ypos, sb_4.xpos, sb_4.ypos) <= (sb_2.ballRadius + sb_4.ballRadius)
        && (sb_2.stringLength > 0.125 && sb_4.stringLength > 0.125)) 
  { sb_2.radSpeed *= -1; break;
  }
  while (dist(sb_3.xpos, sb_3.ypos, sb_4.xpos, sb_4.ypos) <= (sb_3.ballRadius + sb_4.ballRadius)
        && (sb_3.stringLength > 0.125 && sb_4.stringLength > 0.125))
  { sb_3.radSpeed *= -1; break;
  }
} 
 
class StringBall
{ 
  float maxAccel, ballRadius, xpos, ypos, angle, radSpeed, maxRadSpeed, speedFactor, radAccel, stringLength;
  int direction;

  StringBall(float mA, float mRS, float bR, int dir) 
  { 
    angle = 0;
    radSpeed = 0;
    maxAccel = mA;
    maxRadSpeed = mRS;
    ballRadius = bR;
    direction = dir;
  } 
  
  void update() 
  { radAccel = direction * random(0, maxAccel) * (maxRadSpeed - (radSpeed * direction));
    radSpeed = radSpeed + radAccel;
    speedFactor = radSpeed / maxRadSpeed;
    angle += radSpeed;
    stringLength = speedFactor * speedFactor;
    //if (abs(radSpeed) >= maxRadSpeed) radSpeed *= - 0.9;
    //println("speedFactor = " + speedFactor + ", stringLength = " + stringLength);
    xpos = width / 2 * (1 + stringLength * cos(angle));
    ypos = height / 2 * (1 + stringLength * sin(angle));
      
    /*while (count % (rollingRadius * rollingRadius) == rollingRadius * rollingRadius - 1)
    {  radspeed *= random(-2, 2);
       break;
    }*/
    /*fill(255, 32); 
    ellipse(width / 2 + (staticRadius + rollingRadius) * cos(angle), 
    height / 2 + (staticRadius + rollingRadius) * sin(angle), rollingRadius * 2, rollingRadius * 2);
    fill(255, 16);
    ellipse(width / 2, height / 2, staticRadius * 2, staticRadius * 2);*/
    fill(0);
    ellipse(xpos, ypos, ballRadius * 2, ballRadius * 2); 
    //stroke(255);
    //line(width / 2, height / 2, xpos, ypos);
  } 
}