Basics of rendering

Hey

I'm just starting out with developing on Connect IQ and am struggling with rendering shapes (or anything other than text). I've started with the basic watch face with settings template / example.I can happily adding more text fields and see the results but the shapes bit has me stumped!

Reading the API docs it looks like I should be able to just do something along the lines of:

dc.clear();
dc.setColor(Graphics.COLOR_WHITE,Graphics.COLOR_TRANSPARENT);
dc.drawRectangle(50,50,14,14);
dc.fillRectangle(50,100,14,14);

inside of the onUpdate function block

function onUpdate(dc as Dc) as Void {

}

The time displays but no shape. I feel like I must be missing something obvious! Anyone shed some light on the issue.