Instructions:

     Click on the brushes to use them. Click and drag to paint, or right click to fill the whole canvas. Click the pencil to use it. Holding right click with the pencil will erase (draw white). Click the undo button to undo the last stroke or paint fill. Click on the paint splotches in the palette to change colors, or click on the paint tube to select a color using rgb sliders. From the color picker, click the save icon to save the current color to one of the four slots. Click on any of the saved colors to switch to that color. Click on a saved color, then the trashcan icon, to remove it from its slot. Click the bowl of water to reduce the opacity of the paint. Click the paper towel to reset to fully opaque.

The source code is licensed under