[owenmarshall]

I don't like the fill colors. Right now you have three fills - full white, very translucent, and "slightly translucent". But I find it very difficult to judge whether a shape is very translucent or slightly translucent unless all the options are on the screen.

This made the tutorial especially jarring - when I saw a white fill blue, and a slightly translucent red, I ended up confused about yellow... was it the very translucent or slightly translucent?

I'd suggest changing one of the translucent colors to a full fill or some other representation, like stripes/polka dots.