void setup() {
  size(500, 500, P3D);
}
void draw() {
  background(0);
  // position
  translate(width/2, height/2, -width/2);
  // optional fill and lighting colors
  noStroke();
  strokeWeight(4);
  fill(192, 255, 192);
  pointLight(255, 255, 255, 0, -500, 500);
  // rotation driven by built-in timer
  rotateY(millis()/1000.0);
  // draw box
  box(300, 300, 300);
}