Common OEP signatures (VC++ / Delphi / .NET):
"Transfer at 80%," the voice announced.
Third — a mirror facing itself, reflecting reflections until infinity blinks.
The third segment floated forward. It was a vial of grey mist. The Lever.
Most intermediate solvers fail to because they attack the first visible layer with brute force. If you see a string of numbers, you immediately try ASCII. If you see a jumbled sentence, you try Atbash. This is reactive, not strategic.