Opacity should be a scroll bar, and a rectangular selection (eg. for filling/erasing larger areas) would be nice

Thanks! I will keep working on this project. It was kind of a weekend project that spilled over.

I don't really know where to go from here so if you have any ideas pleas feel free to share them.

Get rid of or have an option to disable the jerky lines. It's nearly impossible to draw fine stuff with that.

A single click (without moving) should draw a dot.

A vote to clear the canvas would be cool, removing stuff with that brush is a bit annoying.

Yeah I agree. I plan on implementing a brush system at some point. I will also make it capable of dot drawing.