During the previous century of human civilization, computer games were primitive enough that their entire codebase would fit into a few pages of a magazine. You could play the game by manually retyping the codebase into a text editor.
This is how I learnt loads of great magazines in the 80's in the UK with code in, you spent hours typing it in. It didn't work and you fixed it (that's how I learnt to debug!). The next week the corrections were usually published, good times.
Exactly the same for me, I reckon a lot of 80s kids in the UK who had the right amount of attention span to do it were the same. I remember trying to input the massive list of hex for Tim Follin's 3 channel sound routine that I somehow managed to mistype a part of AND mistype the checksum so that it validated! Cue instant crash every time and disassembling was beyond me at that point.
In the 90s I got an Amiga and discovered the demoscene (basically showing off as mentioned in another comment).
Fast forward another decade and bored at my parents after finishing Uni I dragged my Speccy out of storage and managed to get the Tim Follin music routine running! And found an assembler and did some Z80 assembler demo effects for the lulz.
