float GRAVITY = 0.98;
float resistance = 0.01;

BALL ball = new BALL();

boolean isChk = false;
float lineLength = 100;

void setup() {
  size(400,300);
}
void draw() {
  background(255);
  
  if(isChk && mousePressed){
    float disX = mouseX - ball.x;
    float disY = mouseY - ball.y;
    float seta = atan2(disY, disX);
    float Len = sqrt(disX*disX + disY*disY);
    float F = Len - lineLength;
    float Fx = cos(seta) * F;
    float Fy = sin(seta) * F;
    
    if(F > 0){
      ball.spX += Fx;
      ball.spY += Fy;
      ball.x += Fx;
      ball.y += Fy;
    }
    float late = sin((1-(Len / lineLength)) * PI / 2);
    noFill();
    stroke(255,102,0);
   // curve(ball.x,ball.y,(ball.x + mouseX)/2,(ball.y + mouseY)/2 - F*late, (ball.x + mouseX)/2,(ball.y + mouseY)/2 , mouseX,mouseY);
    
    beginShape();
    vertex(ball.x,ball.y);
    bezierVertex(ball.x,ball.y, (ball.x + mouseX)/2,(ball.y + mouseY)/2 - F*late, mouseX,mouseY);
    endShape();  
    
  }
  
  
  ball.update();
}

void mousePressed(){
  if((mouseX > ball.x - ball.r/2) && (mouseX < ball.x + ball.r/2) && (mouseY > ball.y - ball.r/2) && (mouseY < ball.y + ball.r/2)){
    isChk = true;
  }
}
void mouseReleased(){
  isChk = false;
}

public class BALL {
  
  //x, y property
  public float x, y, spX, spY;
  //elasticity
  float e = 1.0;
  //width
  int r = 50;
  
  BALL () {
    x = 200;
    y = 0;
    spX = 0;
    spY = 0;    
  }
  
  public void update() {
    //add gravity
    spY += GRAVITY;
    //add resistance
    spX -= spX * resistance;
    spY -= spY * resistance;
    
    x += spX;
    y += spY;
    
    int over;
    
    if(x > width){
      over = int(x - width);
      x -= over;
      spX *= -e;
    }
    if(x < 0){
      over = int(x);
      x -= over;
      spX *= -e;
    }
    if(y > height - r/2){
      over = int(y - height + r/2);
      y -= over;
      spY *= -e;
    }
    if(y < 0){
      over = int(y);
      y -= over;
      spY *= -e;
    }
    noFill();
    stroke(0,0,0);
    ellipse(x,y,r,r);
          
  }
  
}