Can anyone explain this code?

I am currently taking a computer class and need help understanding this code and it would help if you could explain what is going in detail in these three classes.

/**

* Implements a falling letter cube for the Ramblecs game

*/

import java.awt.*;

public class FallingCube

{

private int xLeft; // Left margin for cubes

private final int cubeSize;

private int cubeX, cubeY; // Cube coordinates (upper left corner)

private int yStep; // Distance (in pixels) to move down

// in one timer cycle

private int direction= 1;

private static final String letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

private char randomLetter; // Cube letter

public FallingCube(int size, int horzPos)

{

cubeSize = size;

xLeft = horzPos;

yStep = cubeSize / 8;

cubeX = -cubeSize; // off the board --

cubeY = -cubeSize; // not displayed

}

public void setHorizontalPos (int x)

{

x=xLeft;

}

public void start()

{

int i = (int)(Math.random() * letters.length());

randomLetter = letters.charAt(i);

cubeX = 0;

cubeY = yStep; //-cubeSize; // above the board for smooth entry

}

public boolean moveDown()

{

if (cubeY >= 6 * cubeSize)

{

direction=-direction;

}

if (cubeY <= yStep)// land this cube:

{

direction=-direction;

}

cubeY += yStep * direction;

return true;

}

public void draw(Graphics g)

{

int x = xLeft + cubeX;

int y = cubeY;

int j = (int)(Math.random() * 12);

//if (j==0)

//{

//g.setColor(Color.red);

//return true;

//}

g.setColor(Color.red);

g.fill3DRect(x, y, cubeSize-1, cubeSize-1, true);

g.setColor(Color. white);

g.fillRoundRect(x + 5, y + 5, cubeSize - 10, cubeSize - 10,

cubeSize/2 - 5, cubeSize/2 - 5);

g.setColor(Color.darkGray);

String s = String.valueOf(randomLetter);

g.drawString(s, x + cubeSize/2 - 6, y + cubeSize/2 + 5);

}

}

/**

* Implements a panel on which "letter cubes" fall

* in the Ramblecs applet

*/

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class LetterPanel extends JPanel

implements ActionListener

{

private FallingCube cube; //cube2, cube3;

private final int CUBESIZE = 40;

private final int delay = 30;

private Timer t;

public LetterPanel()

{

cube = new FallingCube(CUBESIZE, 2*CUBESIZE);

t = new Timer(delay, this);

//cube2 = new FallingCube(CUBESIZE, 3*CUBESIZE);

//cube3 = new FallingCube(CUBESIZE, 4*CUBESIZE);

}

public void dropCube()

{

cube.start();

//cube2.start();

//cube3.start();

t.start();

}

/**

* Processes timer events

*/

public void actionPerformed(ActionEvent e)

{

boolean moved = cube.moveDown();

//boolean moved2 = cube2.moveDown();

//boolean moved3 = cube3.moveDown();

if (!moved) // "If not moved... "

{

t.stop();

}

/**if (!moved2) // "If not moved... "

{

t.stop();

}

if (!moved3) // "If not moved... "

{

t.stop();

}*/

cube.setHorizontalPos(getWidth()/2-CUBESIZE/2);

//cube2.setHorizontalPos(getWidth()*2-CUBESIZE*2);

//cube3.setHorizontalPos(getWidth()*2-CUBESIZE*2);

repaint();

}

public void paintComponent(Graphics g)

{

super.paintComponent(g); // call JPanel's paintComponent

cube.draw(g);

//cube2.draw(g);

//cube3.draw(g);

}

}

/**

* This is the applet class for the Ramblecs game.

*/

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class Ramblecs extends JApplet

//implements ActionListener

{

private LetterPanel whiteboard;//, yellowboard;

private JButton go;

private ControlPanel controlpanel;

public void init()

{

whiteboard = new LetterPanel();

//yellowboard = new LetterPanel();

//yellowboard.setBackground(Color.green);

whiteboard.setBackground(Color.red);

whiteboard.setSize(600, 200);

//Jbutton go = new JButton("Submit");

controlpanel = new ControlPanel(whiteboard);

//go.addActionListener(this);

Container c = getContentPane();

c.add(whiteboard, BorderLayout.CENTER);

// Box b = Box.createHorizontalBox();

// b.add(whiteboard);

//b.add(yellowboard);

// Container c = getContentPane();

c.add(controlpanel, BorderLayout.EAST);

// c.add(b, BorderLayout.CENTER);

//c.add(go, BorderLayout.NORTH);

}

/**

* Processes Go button events.

*/

/*public void actionPerformed(ActionEvent e)

{

if (Math.random() < 1)

{

whiteboard.dropCube();

}

else

{

//