There is no manual yet, but there are hints:

Object selection
================

Click on an object to select it. If you click on line, you must click within two
or three points from the line.

Click with shift to add object to selected without unselection other objects.
Click with shift to remove object from selected.

Click on the free space and drag to select all objects in a rectangular area.
You can click either with shift, or without it.

If you click on object and move pointer, you draw selected objects.


Mode buttons
============

After creating object, mode usually changes back to pointer. If you want to
create more objects of the same type, you can click mode button with pressed
shift key. This will "lock" mode, so it won't reset to pointer. You can return
to pointer by clicking it or by pressing the ESC key.


Attaching of lines
==================

If you drag end of line over border of an object (currenly only rectangle object,
not line), it attaches to the object. Attachment is indicated by blue color
of the handle.


