Comment by nick__m

For a featureless program it appears to be quite featurefull !

  Opaque and transparencies, at the same time.
  
  Use opaque color for impasto, or glazing over with transparencies, any process, any time.

  Different reflectance behaviour for dense/diluted colors, enjoy the hue shifts as you mix. 
  
  Allow different light source and exposure control of the image.

  Node-Based Brush Engine
  ...