This is really neat. One suggestion, make the two circles in the color wheel that you can drag slightly different (at least). Maybe just line thickness, shape,

This is really neat. One suggestion, make the two circles in the color wheel that you can drag slightly different (at least). Maybe just line thickness, shape, filled/open something to note that dragging one will produce the opposite results from the other. Maybe make only one of them draggable? I know it doesn't really work this way, but I only figured out by accident that dragging to the orange/blue vs blue/orange produced totally different results.