How can max 64k of code be that hard to break?

Look at the internet and use a good search engine. You'll be suprised what source-code you can find.

Evenso, you'll find some source code to get you started writing your own code.

These days, you can find ANYTHING on ANYTHING in ANY language (Asm,c,basic,...)

C-code, asm code ... full sample code, free hardware samples. What more do you need ...

Why trying to hack into a system that is more time-consumable than writing the code yourself?

Have fun coding.