int numBalls = 5;
CradleBall[] balls;
float spacing = 60;

void setup() {
  size(800, 400);
  balls = new CradleBall[numBalls];
  float startX = width / 2 - (numBalls - 1) * spacing / 2;

  for (int i = 0; i < numBalls; i++) {
    float x = startX + i * spacing;
    balls[i] = new CradleBall(x, 100, 150, 20);
  }

  // Pull back first ball
  balls[0].angle = radians(-45);
}

void draw() {
  background(150, 50, 50);  // Green table

  for (int i = 0; i < numBalls; i++) {
    balls[i].update();
    balls[i].display();
  }

  // Detect collisions and transfer momentum
  for (int i = 0; i < numBalls - 1; i++) {
    CradleBall b1 = balls[i];
    CradleBall b2 = balls[i + 1];

    if (b1.isSwingingToward(b2) && b1.isTouching(b2)) {
      // Transfer angular velocity
      b2.angularVelocity = b1.angularVelocity;
      b1.angularVelocity = 0;
    }
  }
}

// --- Cradle Ball class with motion and collision ---
class CradleBall {
  float anchorX, anchorY;
  float length;
  float r;
  float angle = 0;
  float angularVelocity = 0;
  float angularAcceleration = 0;
  float damping = 0.998;
  float gravity = 0.4;

  float ballX, ballY;

  CradleBall(float anchorX, float anchorY, float length, float r) {
    this.anchorX = anchorX;
    this.anchorY = anchorY;
    this.length = length;
    this.r = r;
  }

  void update() {
    angularAcceleration = (-gravity / length) * sin(angle);
    angularVelocity += angularAcceleration;
    angularVelocity *= damping;
    angle += angularVelocity;

    // Calculate actual position of the ball
    ballX = anchorX + sin(angle) * length;
    ballY = anchorY + cos(angle) * length;
  }

  void display() {
    stroke(180);
    line(anchorX, anchorY, ballX, ballY);

    fill(200);  // Silver
    noStroke();
    ellipse(ballX, ballY, r * 2, r * 2);
  }

  boolean isTouching(CradleBall other) {
    float d = dist(this.ballX, this.ballY, other.ballX, other.ballY);
    return d <= this.r * 2 * 0.98;  // Allow a bit of overlap
  }

  boolean isSwingingToward(CradleBall other) {
    return (this.ballX < other.ballX && this.angularVelocity > 0) ||
           (this.ballX > other.ballX && this.angularVelocity < 0);
  }
}