import java.awt.*;
import java.applet.*;

public class coin_flip extends Applet
{

/*  values assigned to white and black  */
static final int WHITE = 1, BLACK = 2, N = 4, N2 = N*N;
static final int NONE = -1;

/*  win determines when the game is won
 *  color determines color of each position
 *  circ = N^2 * 5 circulant matrix
 *  xoff = x offset
 *  yoff = y offset
 *  width = width of applet
 *  height = height of applet
 */
private char win='n';
private static int color[][] = new int[N][N];
private static int circ[][] = new int[N2][5];
private static int xoff, yoff, width, height;

public void init()
  {
  build_circulant();
  init_game();
  Dimension d = size();
  xoff = d.width / N;
  yoff = d.height / (N+1);
  width = d.width;
  height = d.height;
  }

public void paint(Graphics g)
  {
    /*  draw blue buttons  */
  g.setColor(Color.blue);
  g.fillRect(xoff, height-yoff/2, 2*xoff, yoff/2);
  g.setColor(Color.yellow);
  g.drawString("Restart", xoff+25, height-6);

    /*  draw grid  */
  g.setColor(Color.black);
  g.drawLine(width-1,0,width-1,height-yoff);  
  for(int i=0; i<N; ++i)
	  g.drawLine(i*xoff, 0, i*xoff, height-yoff);
  for(int i=0; i<N+1; ++i)
	  g.drawLine(0, i*yoff, width-1, i*yoff);

    /*  draw white and black chips  */
  for(int r=0;r<N;++r)
    for(int c=0;c<N;++c)
	{
        g.setColor(Color.black);
        g.drawOval(r*xoff+1,c*yoff+1,38,38);
	if(color[r][c] == WHITE)
          {
          g.setColor(Color.white);
          g.fillOval(c*xoff+2,r*yoff+2,36,36);
          }
	else
          g.fillOval(c*xoff+2,r*yoff+2,36,36);
	}
  }

public boolean mouseUp(Event evt, int x, int y)
  {
  int col = (x * N) / width;
  int row = (y * (N + 1)) / height;
  int half_row = (y * N * 2) / height;
  Graphics g = getGraphics();

  if(row <= 3 && win == 'n')
    {
    int coin = row * N + col, temp, r, c;
    for(int i=0; i<5; ++i)
      {
      temp = circ[coin][i];
      if(temp != NONE)
        {
        r = temp / N;
        c = temp - r * N;
        if(color[r][c] == WHITE)  color[r][c] = BLACK;
        else                      color[r][c] = WHITE;
        }
      }
    win = winner();
    }

    /*  check if restart button is pressed  */
  if(half_row == N*2-1 && col >= 1 && col <= 2)
    {
    init_game();
    win = 'n';
    }

    /*  Play victory song for winner  */
  if(win == 'y')
    {
    play(getCodeBase(), "audio/coool.au");
    win = 'n';
    g.setColor(Color.red);
    g.drawString("YOU WIN!!!", 2*xoff+15, height-28); 
    }

  repaint();
  return true;
  }


  /*  initialize game  */
void init_game()
  {
    /*  generate initial state of coins  */
  for(int i=0; i<N; ++i)
    for(int j=0; j<N; ++j)
      color[i][j] = (Math.random() < 0.5) ? BLACK : WHITE;
  }


  /*  store the positions of each coin's neighbors in circ  */
void build_circulant()
  {
  int i,j,k,temp;
  int nbrs[] = new int[5];
  for(i=0;i<N;++i)
    for(j=0;j<N;++j)
      {
      temp = i * N + j;
      nbrs[0] = temp;         /*  coin pointed to  */
      nbrs[1] = nbrs[0] + 1;  /*  West  */
      nbrs[2] = nbrs[0] - 1;  /*  East  */
      nbrs[3] = nbrs[0] + N;  /*  South  */
      nbrs[4] = nbrs[0] - N;  /*  North  */
      for(k=0;k<5;++k)
        {
        if (j == 0)       /*  coin on west edge  */
          nbrs[2] = NONE;
        if (j == N-1)     /*  coin on east edge  */
          nbrs[1] = NONE;
        if (i == N-1)     /*  coin on south edge  */
          nbrs[3] = NONE;
        if (i == 0)       /*  coin on north edge  */
          nbrs[4] = NONE;
        circ[temp][k] = nbrs[k];
        }
      }
  }


  /*  winner determines if all coins are WHITE  */
char winner()
  {
  for(int i=0; i<N; ++i)
    for(int j=0; j<N; ++j)
      if(color[i][j] == BLACK)  return 'n';
  return 'y';
  }
}