Looks like it's doing boolean difference on objects as you draw them.

In MoI you would do that by drawing in your cutting object and then using the boolean difference command.

In the future I do want to have different draw modes in MoI to do things like an automatic boolean difference using the object you are drawing but currently you would do those in separate steps. Except for the extrude command, currently when you extrude a face that's part of a solid it is automatically booleaned with the main object as you do the extrusion.

- Michael