ナゾ楽

This is a puzzle game where you "play by solving" ciphers, rather than "learning" them.

From Caesar ciphers to RSA and hashes, you'll intuitively understand the mechanisms of ciphers as you decipher one classical and one modern cipher at a time. You'll experience that "moment of decryption" again and again—calculating and entering the key, using frequency analysis to discern characters, and reverse-looking up tables.

【Included Ciphers】
■ Classical Ciphers (Free, 40 questions total)
・Caesar Cipher (10 questions) — Shifting characters by a certain number. Calculate and enter the shift from the clues.
・Vigenère Cipher (10 questions) — Polyalphabetic using keywords. Declare by guessing the key.
・Substitution Cipher (8 questions) — One-to-one substitution. Approaching with Frequency Analysis
• Transposition Cipher (6 questions) — Uncover the reversal of the order
• Polybius Cipher (6 questions) — Convert to numbers using a 5x5 table, then look up the table in reverse

■ Modern Cryptography
• XOR Cipher (6 questions) — Exclusive OR. XOR with the key to return to plaintext (free)
• Public-key cryptography (Simplified RSA) — Lock with a public key and deduce the message
• Hash function — Experience one-way operation, find inputs that produce the same output (collisions)
• Block cipher (Simplified AES-like) — Relive each step: addition → substitution → sorting

【Features】
• Explanation immediately after solving — Historical background, real-world applications, weaknesses, and a bridge to modern technology
• Step-by-step hints — First, a free review, then step-by-step explanations if you get stuck (designed to leave you with a sense of accomplishment)
• No ads during problem solving, designed to avoid interrupting concentration
• Collection elements with achievement badges and statistics
• Smartphone / tablet compatible
• Supports both Japanese and English (follows device language settings)

【Recommended for】
• Those who like puzzles and riddles
• Students and engineers interested in cryptography and security
• Those who want to quickly train their brains in their spare time

【Connection to the Raku Series】
The third installment in the Raku Series' information-based games. Knowledge of algorithms and data structures will be useful in solving the puzzles.

[About In-App Purchases]
Basic gameplay is free. All stages of classical cryptography and an introduction to modern cryptography are available for free. Hints, ad removal, and a modern cryptography pack are available as premium in-app purchases. No ads are displayed during puzzle gameplay.