I have recently been experimenting with Inkscape (for diagrams) and Opentoonz (for animations). Both are Open Source hence free and both are extremely powerful. There are many tutorial videos available for Inkscape not so many for Opentoonz. Opentoonz was developed by Studio Ghibli and made freely available in 2016 and has a fairly steep learning curve. The result of my experimentation can be seen at https://youtu.be/UF172DZOiWo (Complex Numbers and the Unit Circle). I use Camtasia to compile all the bits and pieces (editing, transitions, screencasts etc) but unfortunately that's not free software and I don't know of an equivalent Open Source piece of software. I use a Mac. I wondered if anyone had any experience (tips, hints, advice etc) in this area that they might wish to share with others?