Fixed mouseout-error

src/game.coffee

@@ -21,6 +21,7 @@ app.game =
     @hud.render()
 
   mousedown: (event)->
+    if @isMouseInView event.x, event.y
       tile = posToTile(event.x, event.y)
       tile.click(event.button)
 
@@ -29,13 +30,23 @@ app.game =
       @currentSelectedTile = tile
 
   mousemove: (event)->
+    if @isMouseInView event.x, event.y
       tile = posToTile(event.x, event.y)
 
       if tile
         if tile != @currentHoveredTile
           tile.moveIn()
-        @currentHoveredTile.moveOut()
+          @currentHoveredTile.moveOut() if @currentHoveredTile
           @currentHoveredTile = tile
+    else
+      @currentHoveredTile.moveOut() if @currentHoveredTile
+      @currentHoveredTile = null
+
+  isMouseInView: (mouseX, mouseY) ->
+    if mouseX < app.width and mouseX >= 0 and mouseY < app.height and mouseY >= 0
+      return true
+
+    false
 
   keyup: (event) ->
     switch event.key