PolyBriX - An open and flexible construction kit ( update 1 - new parts )

It's a flexible prototyping system based on a hexagon shaped brick and two types of octagon shaped bricks, with a snap-fit connecting system that also allows for custom add-ons.
The kit also provides various types of gears, with a flexible snap-fit connecting system, that allows for the chaining and rapid modifications of the mechanisms being build, while remaining tight into position during usage.

Connectors, caps, add-ons, clickers and other useful parts are also provided.

This makes it very useful for teaching spatial reasoning, geared transmissions, counting and for fast building of functional toys, as well.

PolyBriX projects:

Let's build a tractor - build a simple but cute tractor

Geared spinner - the PolyBriX version of a planetary spinner

The counting crab - a crab that counts up to 99 by rotating it's left arm

The distance measuring wagon - a geared vehicle that measures distances

PolyBriX Molecules - create a structure that resembles a Propane molecule

PolyBriX 7-segment digits - build all the digits in a 7-segment style

Update 1: 

• Following the feedback, the parts that were formerly labeled as “tight tolerance” are now the default and only version.
• I've added new parts that allow for the creation of structures that resemble chemical compounds.

• A new project that illustrates the creation of a look-alike Propane Molecule was also added.

System presentation

Here's a picture of the provided bricks:

The all known hexagon shape requires no further presentation - it fills the space with a nice sturdy pattern, with 60 degrees angles.

However, the hexagon can't form right angled grids and doesn't play well with counters and clickers that require 90 degrees angles.

So here comes the octagon -  It can form 90 degrees angles and allows for building more exact gear systems.

An asymmetrical octagonal shape, with 3 plugs and 5 sockets seems to be the most flexible for this task, allowing for creation of a wide range of constructs.

A symmetrical octagonal shape is also provided, although this one probably won't see too much use.

Here's a picture with some of the gears, connectors and add-ons:

New parts will be added as new requirements arise.

Printing instructions:

Walls count: 5
Infill pattern: Zig-Zag
Infill density: 10%

No supports.

I've used PETG, but PLA will probably work as well

Assembly instructions

Make sure all the contact areas ( joints, shafts, etc ) are clean after printing, before starting to work with them.
You can join two bricks by pressing the plug of one into the socket of another or by sliding them vertically. To connect more of them only sliding them vertically will work.
The gears, shafts and connectors can be joined by pressing the plug of one into the socket of the other, firmly. Usually it makes a "click".

Two parts can be detached by bending the joint along the plug, longitudinally or transversely. 
To extract a brick from a grid, push it vertically, along the plugs.

I'd love to see what models you create with these.