Simple Ethereum implementation?

Hey folks. I'm a software engineer with a good working knowledge of modern cryptography.

I'd like to know more about Ethereum from a technical point of view. My question is: is there a "simple" Ethereum implementation that I can execute and work with from A-to-Z that shows the "basics" of Ethereum (not "how to build a smart contract", but Ethereum VM itself).

Do please excuse my ignorance about the project and its scale: I do realize this project has been around for almost a decade and I don't mean to "over-simplify" it but simply to understand it.

Cheers and many thanks, folks