You can just recreate a CS degree and build yourself a foundation from which you can build anything. Before anything else, check out Coursera's Learning How to

You can just recreate a CS degree and build yourself a foundation from which you can build anything. Before anything else, check out Coursera's Learning How to Learn course. You can jump right into CS50 which will provide you with a very strong foundation. If you wished to continue developing your C skills from CS50, you could work your way through K&R, Hanson's C Interfaces and Implementations (in conjunction or following working through material on algorithms and data structures), and learn lower level details by working your way through Bryant and O'Halloron's Computer Systems: A Programmer's Perspective. You can learn proofs from Hammack's Book of Proof, freely available online. From there, you can learn algorithms and data structures from Stanford and/or Princeton's courses on Coursera. The above would be the equivalent of a strong CS minor. From there, you could dive into pretty much anything. The recommendations from https://teachyourselfcs.com/ https://teachyourselfcs.com/ are spot on. Between Coursera, edx, Stanford's Lagunita, and Udacity, you can learn pretty much everything. Be sure to check out Udacity's courses on debugging and testing, as well as anything Peter Norvig teaches. Lagunita will be helpful for CS theory, Computer Networking, Compilers, Databases, and Data Mining. If you were to complete all of the courses I explicitly mentioned, you would have the equivalent of a CS major as long as you study discrete math (Rosen and Epps are the standard texts) and Operating Systems, too.