What ? The Megaprocessor is a micro-processor built large. Very large.
How ? Like all modern processors the Megaprocessor is built from transistors. It's just that instead of using teeny-weeny ones integrated on a silicon chip it uses discrete individual ones like those below. Thousands of them. And loads of LEDs.
Why ? - short answer : Because I want to.
Why ? - long answer : Computers are quite opaque, looking at them it's impossible to see how they work. What I would like to do is get inside and see what's going on. Trouble is we can't shrink down small enough to walk inside a silicon chip. But we can go the other way; we can build the thing big enough that we can walk inside it. Not only that we can also put LEDs on everything so we can actually SEE the data moving and the logic happening. It's going to be great.