Then make a simple interactive applet that animates a square shape, rotating, translating and maybe scaling it. If you're ambitious, make it interactive, so that the square responds to a user's mouse movements in interesting ways.

If you want, you can create a class which extends my BufferedApplet class, and renders using the code below (it's entirely up to you):

   
   int[][] square = new int[4][2];
   int[] edge = {1,3,0,2}; // draw edge to this vertex 
   public void render(Graphics g) {
      for (int i = 0 ; i < 4 ; i++) {
	 square[i][0] = 200 * (i / 2) - 100;
	 square[i][1] = 200 * (i % 2) - 100;
         transform(square[i]);
      }
      g.setColor(Color.white);
      g.fillRect(0,0, bounds().width,bounds().height);
      g.setColor(Color.black);
      for (int i = 0 ; i < 4 ; i++) {
	 int j = edge[i];
         g.drawLine(150+square[i][0],150+square[i][1],
		    150+square[j][0],150+square[j][1]);
      }
   }

   Vector3D vec = new Vector3D();
   Matrix3D mat = new Matrix3D();
   void transform(int[] point) {

      vec.set(0, point[0]);
      vec.set(1, point[1]);

      mat.identity();

      // YOUR CODE GOES HERE

      vec.transform(mat);

      point[0] = (int)vec.get(0);
      point[1] = (int)vec.get(1);
   }