shader_body
{  
    //************************************************************
    // NOTE: the body of this shader will be replaced by MilkDrop
    //       whenever a pre-MilkDrop-2 preset is loaded!
    //************************************************************
    
    // sample previous frame
    ret = tex2D( sampler_main, uv ).xyz;
    
    // darken over time
    ret -= 0.004;
    
    //************************************************************
    // NOTE: the body of this shader will be replaced by MilkDrop
    //       whenever a pre-MilkDrop-2 preset is loaded!
    //************************************************************
}