What are some alternatives?
Krita - Krita is a professional FREE and open source painting program. It is made by artists that want to seaffordable art tools for everyone. Concept art. texture and matte painters, illustrations and comics.
Auryn Ink - Authentic watercolor simulation, the no mess watercolor studio.
MyPaint - MyPaint is a fast, distraction-free, and easy painting tool for digital artists.
ColorMe - Visualize The CSS Color Function
PaintTool SAI - Learn to draw in different ways.
Autodesk SketchBook - SketchBook drawing and painting software provides designers, architects, and concept artists the tools to sketch ideas quickly and create beautiful illustrations.