             context.moveTo(71 * x + 15, 71 * y + 35)
             context.lineTo(71 * x + 55, 71 * y + 35)
             context.stroke()
-            context.strokeStyle = 'black'
+          context.lineWidth = 2
           if @maze.passage_exists([[x, y, z], [x, y, z + 1]])
             # paint up arrow
             context.beginPath()

            context.lineTo(x * 71 + 35, y * 71 + 13)
            context.lineTo(x * 71 + 43, y * 71 + 18)
            context.lineWidth = 2
            context.strokeStyle = 'grey'
            context.stroke()
          if @maze.passage_exists([[x, y, z - 1], [x, y, z]])
            # paint down arrow

            context.moveTo(0.5 + 71 * x, 71.5 + 71 * y)
            context.lineTo(71.5 + 71 * x, 71.5 + 71 * y)
            context.lineWidth = 1
            context.stroke()
          context.strokeStyle = 'grey'
          if @maze.is_finish([x, y, z])
            # paint finish mark 
            context.beginPath()
            context.arc(71 * x + 35, 71 * y + 35, 13.5, 0, 2 * Math.PI, false)
            context.stroke()
