# Moving Balls & Shape Intersection

Hi!
I am trying to find a way to bounce balls off a shape, but I am struggling to do so. I have included an expression at the end of the ‘void move()’ component, but with no success. Any help would be greatly appreciated, thanks!

``````int numBalls = 50;
int numLines = 1;
Ball[] balls = new Ball[numBalls];
Dam dam;

void setup() {
size(640, 360);
for (int i = 0; i < numBalls; i++) {
balls[i] = new Ball(random(0, width), random(height/2, height), 25, i, balls);
}
dam = new Dam();
}

void draw() {
background(255);
for (int i = 0; i < numBalls; i++) {
balls[i].collide();
balls[i].move();
balls[i].display();
}
dam.damdisplay();
}

class Ball {
float spring = 0.05;
float gravity = 0.1;
float friction = -0.9;
float x;
float 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;
}
d = dist(x, y, quad(x, y));
if (d < diameter/2) {
vx = -vx;
}
}

void display() {
stroke(0, 0, 255);
strokeWeight(1);
fill(135, 206, 250);
ellipse(x, y, diameter, diameter);
}
}

class Dam {
void damdisplay() {
stroke(0, 0, 0);
strokeWeight(3);
fill(80, 80, 80);
quad(width/3, height/2, width/2, height/2, width*0.667, height, width/3, height);
}
}

``````
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