[Chriky]

(everything is done in simulators, you don't physically build anything)

Basically you start with only NAND gates available. Using this you have to connect together inputs/outputs etc to make NOT, AND, OR, XOR gates. Then you use these to make gradually more complex chips, such as MUX, HALF-ADDER, ADDER. Then you make an APU etc, eventually making a CPU.

At each stage they tell you the design, but not the implementation.

The assembler targets the CPU you build. The compiler targets the assembly language etc.

You understand the whole stack, and it is a real computer, although simplified as much as possible.