Every lab here comes back to the same literacy: bytes, their hex, and the characters they stand for. This is the bench for that — the ASCII table, a live hexdump -C / xxd, the reverse (hex → text, like xxd -r), and a few classic ciphers for whispering over the wire. Everything runs locally in the page; nothing is sent anywhere.
|printable| with non-printables shown as . — exactly how you read a capture or a carved buffer in Labs 5, 6, 8 and 9.·. Odd/º invalid nibbles are reported, not guessed.0x1b ESC is the one echo-serial.asm watches to bail out.