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                <canvas id="game"></canas>  


  margin: 100px;
  border: 1px solid #000;
  width: 500px;  
  height: 500px;


                # Format for cell and @world:
class GameOfLife
  # default settings
  cell_size: 10 # in px,
  roll_num: 50 # num of cell
  column_num: 50 # num of cell
  draw_rate: 100 # in milliseconds
  born_prob: 0.1 # probability for a life to born
  alive_color: '#999'
  dead_color: '#eee'
  grid_color: '#ccc'
  create: () ->
    @world = @create_world()
  # ------- Initiate The World ------- #
  # callback function to do something on each cell
  travel: (callback) ->
    for row in [0...@roll_num]
      for column in [0...@column_num] this, row: row, column: column
  create_world: ->
    # for every cell, decide that cell being alive depends on chance of born_prob
    @travel (cell) =>
      cell.status = (Math.random() < @born_prob)
  draw_world: ->
    @canvas = document.getElementById 'game'
    @canvas.width = @cell_size * @column_num
    @canvas.height = @cell_size * @roll_num
    @canvas_context = @canvas.getContext '2d'
  # ------- Methods to Create Life ------- #
  draw: (cell) ->
    coords = [cell.row * @cell_size, cell.column * @cell_size, @cell_size, @cell_size]
    @canvas_context.strokeStyle = @grid_color #to ad colors
    @canvas_context.strokeRect.apply @canvas_context, coords
    @canvas_context.fillStyle = if cell.status then @dead_color else @dead_color
    @canvas_context.fillRect.apply @canvas_context, coords 
    @canvas_context.fillStyle = if cell.status then @alive_color else @dead_color
    @canvas_context.arc(cell.row * @cell_size, cell.column * @cell_size, @cell_size/4, 0, 2 * Math.PI, false)
  # game loop forever
  loop: =>  
    @world = @travel (cell) =>
      cell = @world[cell.row][cell.column]
    setTimeout(@loop, @draw_rate)
  # ------- Logic and Patterns of Life ------- #
  # make decision for next step, return the whole cell
  dead_or_alive: (cell) ->
    neighbor = @count_neighbor(cell)
    cell = @review_status(cell, neighbor)
  count_neighbor: (cell) ->
    neighbor = 0
    for row in [-1..1]
      for column in [-1..1]
        neighbor_row = cell.row + row
        neighbor_column = cell.column + column
        # (row or column) means except itself
        ++neighbor if (row or column) and @isAlive(neighbor_row, neighbor_column)
  # check if that cell is alive (true/false)
  isAlive: (row, column) ->
    # check if coordinates is inside the boundary
    if @world[row] isnt undefined and @world[row][column] isnt undefined
      # check the current status of the neighbor
      result = @world[row][column].status
    else result = false # if coordinates is undefined
  # game rules
  review_status: (cell, neighbor) ->
    # input cell and num of neighbor, return the whole cell
    # if cell is alive
    #   if neighbor < 2 then die <-- under-population!
    #   if neighbor is 2 or 3 then alive
    #   if neighbor > 3 then die <-- overcrowding!
    # if cell is dead and neighbor is 3 then live <-- reproduction!
    # copy the cell object first
    cell = { row: cell.row, column: cell.column, status: cell.status }
    if neighbor < 2 or neighbor > 3 then cell.status = false
    else if neighbor is 3 then cell.status = true
    # all others remain the same status

# implement GOL
gol = new GameOfLife