Ask HN: What are comprehensive resources to learn digital product design?

I'm a software developer (mainly web) with an interest in design. I believe I have a good intuition from my experience working with designers, but I would like to turn this into more solid knowledge.

I'm struggling to find a comprehensive resource that teaches me graphic design and digital product design foundations such as color theory, spacing, rhythm, and most likely other concepts I haven't heard about yet.

I need something that guides me through the world of design, and not an aggregation of articles (of which I already read a lot).

Any ideas?