I would like to know what a good book, paper, website, etc. would be that describes, for each letter in the Hebrew alphabet, what is and what is not acceptable for the character. I see a lot of variation in the structure of symbols in fonts, but I'm not sure what is the technically correct sort of "reference" implementation of the alphabet, from which everything else is based. Looking for a resource on that, preferably free/open, but if there is only ones to be purchased then that would be okay too.
Specifically in reference to language learning, I would like to know how to properly write the language, both in block and cursive writing. This means knowing the details of how the letters can be constructed, what is valid/invalid, etc. I can learn at a "rough" level from videos and the internet, but I would like to get more clarity on the specific details and rules of writing the characters.