Expresii (www.expresii.com) is a new painting app featuring advanced brush and ink (watercolor) simulation for Windows. This Gumroad 'purchase' is only for getting a free trial license key. A Trial Key allows you to save your work.
You'll get a PDF with a download link or you can download it from http://www.expresii.com/download.html
Warning: Expresii uses modern GPU for accelerated processing therefore it may not work correctly on older computers. Get this free key to test artwork saving and make sure it really works well on your computer before any commitment.