Code Message Generator

Pendulum Key Cipher — Encrypt & Decrypt

Single‑file • Client‑side • ASCII A–Z only

Invented by Thaddeus Mitchell.

Key (digits; empty = 2112 )

Example patterns: 2112 12321 32123. Only digits 1–9 allowed.

Input

Only letters A–Z/a–z are shifted; other characters are left unchanged.

Output

How it works(click to expand)

The Pendulum Key cipher applies a repeating sequence of Caesar shifts across letters, then flips the direction each full cycle. With key 2112 the shifts go +2, +1, +1, +2 then −2, −1, −1, −2 , then repeat. Non‑letters are copied unchanged. Decrypting reverses the sign.

 // Pseudocode
for each char c in text:
  if isLetter(c):
    shift = sign * seq[j]
    if decrypt: shift = -shift
    out += shiftChar(c, shift)
    j = (j+1) % len(seq)
    if j == 0: sign = -sign
  else:
    out += c