Katie, this intended more for those who already have some coding experience, but maybe of some use (at least to get the gist of it).
https://learnxinyminutes.com/docs/c++/
Was brought to my attention as link (to Python I think) in Vapoursynth docs.
(Lots more Learn X in Y minutes, from the home page).
Not interactive.
EDIT: Took me way more than 2 days to learn C.
EDIT: Actually, above was for CPP, here for C:-
https://learnxinyminutes.com/docs/c/
And the parent page with bucket loads more subjects:-
https://learnxinyminutes.com/