Summary

Drawing:

Specify points with pt(x,y)
Specify rectangles with rect(x,y,width,height)
Draw using drawline, drawrect, fillrect etc.
Change drawing colour, e.g. setcolour(Green)

Windows:

Create windows with newwindow
E.g. newwindow("Name", rect(0,0,400,300), StandardWindow)
Add a redraw callback using setredraw(w, fn)
Show the window on screen with show(w)
End your main function by calling mainloop()