Where can I find material to understand/study, unistroke / multistroke gesture recognition ? C#

This is my first post and looking for some guidance. I wanted to to implement gesture recognition for varied shapes and symbols that would be drawn via touch on screen for a small project. I understand there are different tool kits etc out there and on asset store that will help implement this but ive gotten curious on how it actually works and cant find much online yet.

I was hoping someone with this knowledge or knowledge of where i can obtain such study material that would be in an easy-ish digestible format for me.

I currently programme in C# using unity engine and have had some experience in C++.

Thanks to anyone who can point me in the right direction whether it be books , papers or video tutorials!