int[][][] board;
int gW = 100;
int gH = 100;
int sW = 300;
int sH = 300;
int cellW, cellH;
int C=0;

void setup()
{
  float density = .55;
  size(sW,sH);
  cellW = sW/gW;
  cellH = sH/gH;
  board = new int[gW][gH][2];
  framerate(15);
  for (int y=0; y < gH; y++)
  for (int x=0; x < gW; x++)
  {
    board[x][y][0] = 0;
    board[x][y][1] = 0;
  }
  board[52][52][0] = 1;
  board[52][53][0] = 1;
  board[52][54][0] = 1;
  board[53][52][0] = 1;
  board[51][53][0] = 1;
  
  board[52][52][1] = 1;
  board[52][53][1] = 1;
  board[52][54][1] = 1;
  board[53][52][1] = 1;
  board[51][53][1] = 1;
}
void randomize(float density)
{
  int r1, r2;
  for (int i=0;i<gW*gH*density;i++)
  { r1 = (int)random(gW);
    r2 = (int)random(gH);
    board[r1][r2][0] = 1;
    board[r1][r2][1] = 1;
  }
}
void loop()
{
  background(235,242,245);
  fill(30,115,175);
  //stroke(0);
  noStroke();
  for (int y=1; y < gH; y++)
  for (int x=1; x < gW; x++)
    if (board[x][y][C]==1) rect(x*cellW,y*cellH,cellW,cellH);
  step();
}
void mousePressed()
{
  randomize(.25);
}
void step()
{
  C = (C+1)%2;
  int tn;
  for (int y=0; y < gH; y++)
  for (int x=0; x < gW; x++)
  {
    tn = neighbors(x,y);
//    if (x == 3 && y ==3) print("n = " + tn + "\n");
    if (tn > 3) board[x][y][C]=0;
    else if (tn == 3) board[x][y][C]=1;
    else if (board[x][y][(C+1) % 2]==1 && tn ==2) board[x][y][C]=1;
    else board[x][y][C]=0;
   
    //if (board[x][y]==1) rect(x*cellW,y*cellH,cellW,cellH);//point(x,y);
  }
}

int neighbors(int x, int y)
{
  int n = 0;
  for (int dy=-1; dy<=1; dy++)
  {
    for (int dx=-1; dx<=1; dx++)
    {
      n += board[abs(x+dx) % gW][abs(y+dy) % gH][(C+1) % 2];
    }
  }
  n -= board[x][y][(C+1) % 2];
  return n;
}