https://people.inf.ethz.ch/wirth/Oberon/index.html by Niklaus Wirth
Oberon is a beautifully designed programming language. It is both a high and low level language: Niklaus Wirth used it for his OS.
The Oberon manual (ProgrammingInOberon.pdf) is only 64 pages long. It explains all the features of the language and it's extremely easy to understand.
Oberon truly feels like the one imperative language to rule them all. I really wonder if the complexity of the other languages (Rust, Go, ...) is worth it.
Oberon feels a bit like Lua but with a type system.
I want to bring Oberon to modern architecture, maybe on top of another language (Go?) to make it easier to run on different OS.