I managed to figure out hacking NES Game Genie codes pretty well at about 14, even without any documentation besides the Genie book itself. I'd read enough lib

I managed to figure out hacking NES Game Genie codes pretty well at about 14, even without any documentation besides the Genie book itself. I'd read enough library books about computers to understand binary and hexadecimal. So from the existing codes in the Genie book (like 5 lives / 99 lives / etc), I figured out how those values were coming from some of the letters defining binary/hex values. So I could extrapolate to more codes for different values. And from there I realized the other letters must specify the memory location, so I could bump that too and change some different stats that weren't in the book. I particularly had fun with Final Fantasy 1, where I figured out how to set inventory values and even tried out-of-range values and got items that didn't exist. What I didn't know until years later was the difference between 6-letter (3 byte) and 8-letter (4-byte) codes. The additional byte in the longer code specifies a value such that the override takes place only if the memory location already equals that value. The purpose is to handle bankswitching (memory mappers), to have the code active only when the correct memory bank is. In practice, what this meant was that randomly trying 8-letter codes almost never did anything (1/256 that you happen to hit the right value) and so I only tried the shorter ones, and found a few weird effects from them.