   attribute vec4 aColor;
 
   varying lowp vec4 vColor;
+  varying lowp vec2 vLayer;
   uniform  vec4 uViewport;
 
   mat4 viewportScale = mat4(2.0 / uViewport.z, 0, 0, 0,    0, -2.0 / uViewport.w, 0,0,    0, 0,1,0,    -1,+1,0,1);

  init: ->
    @bind 'Draw', @_drawGradient
    if @has 'WebGL'
      @_establishShader 'Gradient',
        GRADIENT_FRAGMENT_SHADER,
        GRADIENT_VERTEX_SHADER,
        GRADIENT_ATTRIBUTE_LIST

  _drawGradient: (e) ->
    if e.type is 'webgl'
      e.program.writeVector('aColor',
        @_topColor._red/255,
        @_topColor._green/255,
        @_topColor._blue/255,
        @_topColor._strength,

        @_bottomColor._red/255,
        @_bottomColor._green/255,
        @_bottomColor._blue/255,
        @_bottomColor._strength
      )

  topColor: (color) ->
