94

int numBalls = 12;
float spring = 0.05;
float gravity = 0.03;
float friction = -0.9;
Ball[] balls = new Ball[numBalls];

void setup(){
size(500,300);
noStroke();
smooth();
for(int i = 0; i < numBalls; i++){
balls[i] = new Ball(random(width),random(height),random(20,40),i,balls);
}
}

void draw(){
background(0);
for(int i = 0; i < numBalls; i++){
balls[i].collide();
balls[i].move();
balls[i].display();
}
}

void mousePressed(){
save("94.jpg");
}

class Ball{
float x,y;
float diameter;
float vx = 0;
float vy = 0;
int id;
Ball[] others;

Ball(float xin, float yin, float din, int idin, Ball[] oin){
x = xin;
y = yin;
diameter = din;
id = idin;
others = oin;
}

void collide(){
for(int i = id + 1; i < numBalls; i++){
float dx = others[i].x-x;
float dy = others[i].y-y;
float distance = sqrt(dx*dx + dy*dy);
float minDist = others[i].diameter/2+diameter/2;
if(distance < minDist){
float angle = atan2(dy,dx);
float targetX = x + cos(angle) * minDist;
float targetY = y + sin(angle) * minDist;
float ax = (targetX - others[i].x) * spring;
float ay = (targetY - others[i].y) * spring;
vx -= ax;
vy -= ay;
others[i].vx += ax;
others[i].vy += ay;
}
}
}


void move(){
vy += gravity;
x += vx;
y += vy;
if(x + diameter/2 > width){
x = width - diameter/2;
vx *= friction;
}
else if(x - diameter/2 < 0){
x = diameter/2;
vx *= friction;
}
if(y + diameter/2 > height){
y = height - diameter/2;
vy *= friction;
}
else if(y - diameter/2 < 0){
y = diameter/2;
vy *= friction;
}
}

void display(){
fill(255,204);
ellipse(x,y,diameter,diameter);
}
}