// A function to rotate a vector
public void rotateVector(PVector v, float theta) {
float m = v.mag();
float a = v.heading2D();
a += theta;
v.x = m * PApplet.cos(a);
v.y = m * PApplet.sin(a);
}
// Wraparound
public void borders() {
if (loc.x < -r) loc.x = width + r;
if (loc.y < -r) loc.y = height + r;
if (loc.x > width + r) loc.x = -r;
if (loc.y > height + r) loc.y = -r;
}