Cube stage; // external large cube
  int cubies = 20;
  Cube[]c = new Cube[cubies]; // internal little cubes
  color[][]quadBG = new color[cubies][6];
  
  // Controls cubie's movement
  float[]x = new float[cubies];
  float[]y = new float[cubies];
  float[]z = new float[cubies];
  float[]xSpeed = new float[cubies];
  float[]ySpeed = new float[cubies];
  float[]zSpeed = new float[cubies];
  
  // Controls cubie's rotation
  float[]xRot = new float[cubies];
  float[]yRot = new float[cubies];
  float[]zRot = new float[cubies];
  
  // Size of external cube
  float bounds = 300;
  
  void setup() {
    size(640, 360, P3D);
    
    for (int i = 0; i < cubies; i++){
      // Each cube face has a random color component
      float colorShift = random(-75, 75);
      quadBG[i][0] = color(0);
      quadBG[i][1] = color(51);
      quadBG[i][2] = color(102);
      quadBG[i][3] = color(153);
      quadBG[i][4] = color(204);
      quadBG[i][5] = color(255);
  
      // Cubies are randomly sized
      float cubieSize = random(5, 15);
      c[i] =  new Cube(cubieSize, cubieSize, cubieSize);
  
      // Initialize cubie's position, speed and rotation
      x[i] = 0;
      y[i] = 0; 
      z[i] = 0;
  
      xSpeed[i] = random(-1, 1);
      ySpeed[i] = random(-1, 1); 
      zSpeed[i] = random(-1, 1); 
  
      xRot[i] = random(40, 100);
      yRot[i] = random(40, 100);
      zRot[i] = random(40, 100);
    }
    
    // Instantiate external large cube
    stage =  new Cube(bounds, bounds, bounds);
  }
  
  void draw(){
    background(50);
    lights();
    
    // Center in display window
    translate(width/2, height/2, -130);
    
    // Outer transparent cube
    noFill(); 
    
    // Rotate everything, including external large cube
    rotateX(frameCount * 0.001);
    rotateY(frameCount * 0.002);
    rotateZ(frameCount * 0.001);
    stroke(255);
    
    // Draw external large cube
    stage.create();
  
    // Move and rotate cubies
    for (int i = 0; i < cubies; i++){
      pushMatrix();
      translate(x[i], y[i], z[i]);
      rotateX(frameCount*PI/xRot[i]);
      rotateY(frameCount*PI/yRot[i]);
      rotateX(frameCount*PI/zRot[i]);
      noStroke();
      c[i].create(quadBG[i]);
      x[i] += xSpeed[i];
      y[i] += ySpeed[i];
      z[i] += zSpeed[i];
      popMatrix();
  
      // Draw lines connecting cubbies
      stroke(0);
      if (i < cubies-1){
        line(x[i], y[i], z[i], x[i+1], y[i+1], z[i+1]);
      }
  
      // Check wall collisions
      if (x[i] > bounds/2 || x[i] < -bounds/2){
        xSpeed[i]*=-1;
      }
      if (y[i] > bounds/2 || y[i] < -bounds/2){
        ySpeed[i]*=-1;
      }
      if (z[i] > bounds/2 || z[i] < -bounds/2){
        zSpeed[i]*=-1;
      }
    }
  }