Thanks for the links! Most of the submitted approaches don't even mess with the ELF binary structure. But even if you don't do that, there's a lot you can learn by optimizing (sometimes doing something with more instructions instructions actually result in a smaller binary because of shorter opcodes).

It was the first time I really messed around with x86 assembly and I learned a lot during the progress :)

Edit: Wording

Edit2: Also note that for this challenge you need to submit NASM assembly, and not the resulting binary. So you can't resort to hex editing the binary itself.