Reversing

A single APK whose UI claims there’s nothing to see — the flag is split into three pieces hidden in a MainActivity field, a string resource, and a Compose theme getter.

An idle/clicker TCP game whose shop checks affordability against a stale cached balance but deducts from a fresh re-read; racing two sessions as the same user underflows an unsigned long to ~1.8e19 bits and buys the flag.

A UPX-packed, unstripped crackme lays its 44-byte check out as 44 independent per-character functions; emulating each with Unicorn brute-forces the flag one byte at a time, sidestepping a rand()-based anti-dynamic trap.

A stripped compiler for an invented language is reverse-engineered from its error strings and codegen templates; the recovered grammar exposes an intended read file primitive that simply prints flag.txt — no exploit required.