Created as a free solid CAD tool related to their much more expensive flagship Autodesk Inventor software, 123D Design offers a hobbyist introduction to CAD tools that makes it really easy to create things like enclosures, cases, and simple mechanical models without the steeper learning curve of the more advanced apps. There is a premium option that offers more tools and export formats — including creating 2D plans / documentation for models and access to a larger 123D Content Library for prebuilt parts.
They have created a number of helpful tutorial videos to help users get started here.
Make a robot friend with Adafruit’s CRICKIT – A Creative Robotics & Interactive Construction Kit. It’s an add-on to our popular Circuit Playground Express, FEATHER and other platforms to make and program robots with CircuitPython, MakeCode, and Arduino. Start controlling motors, servos, solenoids. You also get signal pins, capacitive touch sensors, a NeoPixel driver and amplified speaker output. It complements & extends your boards so you can still use all the goodies on the microcontroller, now you have a robotics playground as well.