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    Click a cell to generate the flow field
    Pick any point on the map and follow the arrows back to the start position
    The direction buttons will generate a flow off the grid, useful for chaining grids together.

              .grid {
  height: 400px;
  position: relative;
  width: 400px;
  margin: 0 auto;

.grid-row {
  overflow: auto;

.grid-cell {
  background-color: #eee;
  color: #333;
  float: left;
  font-size: 14px;
  height: 18px;
  width: 18px;
  text-align: center;
  line-height: 16px;
  border-width: 1px;
  border-style: solid;
  border-color: #fff #ccc #ccc #fff;
  text-shadow: 1px 1px 0 #fff;
  cursor: pointer;
  &:hover {
    background-color: #ccc;
  &.grid-wall {
    background-color: #800;

              seed = 1437089783193 
#seed = +(new Date)
rng = new Chance seed

class GridView
  directionLookup: {
    '1_0': '↑'
    '2_1': '→'
    '1_2': '↓'
    '0_1': '←'
    '2_0': '↗'
    '2_2': '↘'
    '0_2': '↙'
    '0_0': '↖'
    '1_1': '☉'

  constructor: (@selector, @gridData) ->
    @$el = $('<div>').addClass 'grid'
    @flowField = new FlowField @gridData

  render: ->
    {nodes, width, height} = @gridData
    for y in [0...height]
      $rowEl = @buildRow()
      for x in [0...width]
        $cellEl = @buildCell x, y, nodes[y][x]
        $rowEl.append $cellEl
      @$el.append $rowEl
    $(@selector).append @$el

  buildRow: ->
    $('<div>').addClass 'grid-row'

  buildCell: (x, y, gridCell) ->
    $cellEl = $('<div>')
    $cellEl.addClass 'grid-cell'
    $cellEl.data {x, y}
    unless gridCell.data.open
      $cellEl.addClass 'grid-wall'

  addEventListeners: ->
    @$el.on 'click', '.grid-cell', (event) =>
      $el = $ event.currentTarget
      x = $el.data 'x'
      y = $el.data 'y'
      @beginFill x, y
    $('#northFlow').click => @directionFlow 0, -1
    $('#eastFlow').click => @directionFlow 1, 0
    $('#southFlow').click => @directionFlow 0, 1
    $('#westFlow').click => @directionFlow -1, 0

  directionFlow: (vX, vY) ->
    @flowField.directionFlow vX, vY, @markCost, @markFlow

  beginFill: (x, y) ->
    @flowField.process x, y, @markCost, @markFlow

  markFlow: (x, y, vector) =>
    $cellEl = @$el.find('.grid-row').eq(y).find('.grid-cell').eq(x)
    directionIndex = "#{vector.x + 1}_#{vector.y + 1}"
    $cellEl.html @directionLookup[directionIndex]

  markCost: (x, y, iteration) =>
    $cellEl = @$el.find('.grid-row').eq(y).find('.grid-cell').eq(x)
    $cellEl.addClass 'grid-cell-marked'
    $cellEl.html iteration

mapData = (width, height) ->
  data = []
  for y in [0...height]
    data[y] = []
    for x in [0...width]
      data[y][x] = rng.bool {likelihood: 90}

grid = new Grid mapData(20, 20)
gridView = new GridView '#container', grid


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