BlocksCAD is a free CAD package that combines the sort of visual block programmatic structure of the Scratch programming language, with CAD features of OpenSCAD. BlocksCAD does not require registration or an account to use it; however, creating an account is free, and allows you to save your BlocksCAD projects in BlocksCAD for later reference.
BlocksCAD may be conveniently accessed from the Polar Cloud; see Section 6.1.1.
BlocksCAD objects may be conveniently exported directly to the Polar Cloud; see Section 6.1.2.
Clicking the BlocksCAD logo link on Polar Cloud objects exported directly from BlocksCAD will open a new window to BlocksCAD with the BlocksCAD object blocks re-instantiated, for especially convenient changes or manipulations within BlocksCAD. Or as with any CAD package supporting industry-standard .stl files, you may also import other Polar Cloud objects into BlocksCAD, to edit or manipulate them using BlocksCAD. See Section 6.1.3 (and for objects created in BlocksCAD using BlocksCAD’s Import STL file into Current Project feature, see also the additional discussion in Section 6.1.4).
And for a detailed introduction to using BlocksCAD for creative and educational purposes, see From Dreams to Designs: The Polar3D Introduction to BlocksCAD.