diff --git a/nikoli.rb b/nikoli.rb
index 73cb521..8a35645 100755
--- a/nikoli.rb
+++ b/nikoli.rb
@@ -10,6 +10,7 @@ require 'sass'
 GAMES = %i{nurikabe sudoku}
 
 get('/application.css') { scss :application }
+get('/application.js') { coffee :application }
 
 get('/') { slim :index, locals: {games: GAMES} }
 
diff --git a/views/application.coffee b/views/application.coffee
new file mode 100644
index 0000000..0f683ad
--- /dev/null
+++ b/views/application.coffee
@@ -0,0 +1,55 @@
+window.Nikoli = Nikoli = {}
+
+class Nikoli.Stream
+  constructor: (@game) ->
+    @cells = []
+
+  calculate: (cell) ->
+    value = @game[cell.x][cell.y]
+    @cells = []
+    @type = if value < 0 then 'black' else 'white'
+
+    cell = {x: cell.x, y: cell.y, value: value}
+    cells_to_process = [cell]
+
+    while cells_to_process.length > 0
+      cell = cells_to_process.pop()
+      cells_to_process = cells_to_process.concat @process(cell) unless @include(cell)
+
+
+    @cells
+
+  checkCell: (cell, value) ->
+    0 <= cell.x < @game.length && 0 <= cell.y < @game[cell.x].length &&
+      (value < 0 && @game[cell.x][cell.y] < 0 || value >= 0 && @game[cell.x][cell.y] >= 0)
+
+  empty: ->
+    @cells.length == 0
+
+  getCell: (cell, value) ->
+    {x: cell.x, y: cell.y, value: @game[cell.x][cell.y]} if @checkCell(cell, value)
+
+  include: (cell) ->
+    @cells.indexOf("#{cell.x};#{cell.y}") >= 0
+
+  length: ->
+    @cells.length
+
+  process: (cell) ->
+    @cells.push("#{cell.x};#{cell.y}")
+
+    x = cell.x
+    y = cell.y
+    value = cell.value
+
+    cells_to_add = []
+    tmp_cell = @getCell({x: x+1, y: y}, value)
+    cells_to_add.push tmp_cell if tmp_cell?
+    tmp_cell = @getCell({x: x-1, y: y}, value)
+    cells_to_add.push tmp_cell if tmp_cell?
+    tmp_cell = @getCell({x: x, y: y+1}, value)
+    cells_to_add.push tmp_cell if tmp_cell?
+    tmp_cell = @getCell({x: x, y: y-1}, value)
+    cells_to_add.push tmp_cell if tmp_cell?
+
+    cells_to_add
diff --git a/views/layout.slim b/views/layout.slim
index 387fb39..b51492e 100644
--- a/views/layout.slim
+++ b/views/layout.slim
@@ -5,6 +5,7 @@ html
     meta charset="utf-8"
     meta name="viewport" content="initial-scale=1.0, user-scalable=yes"
     link rel="stylesheet" media="all" href="/application.css"
+    script type="text/javascript" src="/application.js"
   body
     div#main
       == yield
diff --git a/views/nurikabe.coffee b/views/nurikabe.coffee
index 48d903a..6800ea9 100644
--- a/views/nurikabe.coffee
+++ b/views/nurikabe.coffee
@@ -31,7 +31,7 @@ window.Nurikabe = class Nurikabe
     solution = @toArray()
     errors = []
     processed_cells = []
-    black_stream = new Stream(solution)
+    black_stream = new Nikoli.Stream(solution)
     white_walls = []
 
     for i in [0...solution.length]
@@ -48,7 +48,7 @@ window.Nurikabe = class Nurikabe
           if white_walls.some((wall) -> wall.include({x: i, y: j}))
             errors.push {row: i, column: j, message: 'Each wall must contain exactly one numbered cell.'}
           else
-            wall = new Stream(solution)
+            wall = new Nikoli.Stream(solution)
             wall.calculate({x: i, y: j})
 
             if wall.length() != cell
@@ -97,57 +97,3 @@ window.Nurikabe = class Nurikabe
             0
         else
           parseInt(cell.innerHTML)
-
-class Stream
-  constructor: (@game) ->
-    @cells = []
-
-  calculate: (cell) ->
-    value = @game[cell.x][cell.y]
-    @cells = []
-    @type = if value < 0 then 'black' else 'white'
-
-    cell = {x: cell.x, y: cell.y, value: value}
-    cells_to_process = [cell]
-
-    while cells_to_process.length > 0
-      cell = cells_to_process.pop()
-      cells_to_process = cells_to_process.concat @process(cell) unless @include(cell)
-
-
-    @cells
-
-  checkCell: (cell, value) ->
-    0 <= cell.x < @game.length && 0 <= cell.y < @game[cell.x].length &&
-      (value < 0 && @game[cell.x][cell.y] < 0 || value >= 0 && @game[cell.x][cell.y] >= 0)
-
-  empty: ->
-    @cells.length == 0
-
-  getCell: (cell, value) ->
-    {x: cell.x, y: cell.y, value: @game[cell.x][cell.y]} if @checkCell(cell, value)
-
-  include: (cell) ->
-    @cells.indexOf("#{cell.x};#{cell.y}") >= 0
-
-  length: ->
-    @cells.length
-
-  process: (cell) ->
-    @cells.push("#{cell.x};#{cell.y}")
-
-    x = cell.x
-    y = cell.y
-    value = cell.value
-
-    cells_to_add = []
-    tmp_cell = @getCell({x: x+1, y: y}, value)
-    cells_to_add.push tmp_cell if tmp_cell?
-    tmp_cell = @getCell({x: x-1, y: y}, value)
-    cells_to_add.push tmp_cell if tmp_cell?
-    tmp_cell = @getCell({x: x, y: y+1}, value)
-    cells_to_add.push tmp_cell if tmp_cell?
-    tmp_cell = @getCell({x: x, y: y-1}, value)
-    cells_to_add.push tmp_cell if tmp_cell?
-
-    cells_to_add