Welcome to the forum
I’m not sure I have any great answers for you but I think this an interesting conversation so I hope that other members will join in.
The short answer is that, no, I don’t know of any adult resources for Scratch beyond guides for teachers. These guides tend to be about lesson plans and project ideas rather than teaching Scratch to teachers.
As you rightly point out, Scratch is designed for 8 to 16 year olds so it’s not too surprising that there aren’t many/any adult focused resources.
My concern for you is that Scratch may not be capable enough for the games you want to create in the future. It’s great for simple animation and simple games but I definitely bump into limitations when trying to create even slightly more advanced stuff.
One good example is the size of the stage, 480 x 360 pixels is pretty small. For example, if you were creating a word search game then you wouldn’t get many words within that space.
Scratch is great for quick projects that take an hour or two to code but I find, that beyond that, you end up with a lot of code blocks which get messy and hard to work with.
Text based languages (E.g. Python etc) have ways to separate and reuse code as well as overcoming may other Scratch limitations.
Ok, so where next?
I’ve never used it but there is an extended implementation of Scratch (Read: spin-off) called Snap! It looks very similar so your Scratch learning won’t be wasted but it has added capabilities (e.g. larger stage, more functions) that make it suitable for a serious introduction to computer science for high school or college students.
Take a look at https://snap.berkeley.edu/index
and they have a manual here: https://snap.berkeley.edu/snapsource/he ... Manual.pdf
If you wanted to investigate other visual based languages (rather than text based languages like Python, C++ etc) then try searching online for "online game builder”. These systems tend to lean towards creating arcade games but you may find something that suits your needs and they can be a lot of fun to test out.
If you’re looking at Python then be sure to check out the Code Club Python projects here: https://projects.raspberrypi.org/en/codeclub
Also Microsoft have a video course on Python here: https://cloudblogs.microsoft.com/openso ... beginners/
Good luck and let us know how you get on.