BALL B  = new BALL(new pt(400,800), new vec(0,0), 25);
BALL P1 = new BALL(new pt( 40,120), new vec(0,0) , 5);
BALL P2 = new BALL(new pt(120,120), new vec(0,0) , 5);

float gravity = 0.009; float shock = 0.86; float fric = 0.999;

void setup(){ size(800, 800); }

void draw()   {
    background (150,100,30);
    P1.paint(); P2.paint();
    B.move();  B.pushOff(P1);   B.pushOff(P2);    B.clash();     B.paint();
    if (B.stopped()) {line (mouseX,mouseY,B.C.x,B.C.y); };
    };

void mousePressed() { if (B.stopped()) {B.V.x = (mouseX - B.C.x) / 70.0;  B.V.y = (mouseY - B.C.y) / 70.0; }; } 

class BALL {pt C ; vec V ; float r; 
    BALL (pt PC, vec PV, float pr) {C=PC; V=PV; r=pr;};
   void paint() { if (V.norm() == 0) {fill(color(5,250,30));} else {fill(color(250,30,10)); } ;  C.show(r);  }; 
    void move() { V.y= V.y+gravity; C.x=C.x+V.x; C.y=C.y+V.y; };
    void clash (){
      if (C.x>width-r) {C.x=2 * (width-r) - C.x; V.x=-V.x; V.x= V.x * shock;};
      if (C.y<r) {C.y=2 * r -C.y; V.y=-V.y; V.y= V.y * shock;};
      if (C.x<r) {C.x=2 * r -C.x; V.x=-V.x; V.x= V.x * shock;};
      if (C.y>height-r) {C.y=2 * (height-r) - C.y; V.y=-V.y; V.y= V.y * shock;};
      if ((abs(V.y)<0.5) && (abs( height - r - C.y)<1.0 )) {V.y = 0; V.x = V.x * fric; if (abs(V.x)<0.6) {V.x = 0;};};     
      };
     void pushOff(BALL O) { 
      if (C.vecTo(O.C).norm() < r+O.r)    {
         vec T = V.make(); T.unit();   
         vec N = T.make(); N.left(); 
        float h = dot(C.vecTo(O.C),N); float w = sqrt(sq(r+O.r)-sq(h));
        T.mul(-w);  N.mul(-h);  T.add(N);       
        T.unit(); T.mul(-2*dot(T,V));   V.add(T);  
        }; 
      };
      boolean stopped() {return(V.norm()==0);};  
    }      // end of class BALL