What are some alternatives?
When comparing Pixel Pix and Pixel Art to CSS, you can also consider the following products
Responsive Pixel Art - It's exactly that... responsive pixel art 🙃
Aseprite - Aseprite is an art program dedicated to the creation of pixel art.
piCSSel-art - Draw pixel art with CSS!
Pixel Art Studio - A purpose-built drawing tool for pixel artists
Pixilart - A drawing app for delightfully retro pixel art
Piskel - Piskel is a website where designers online create sprites or pixel art.