Codemaker: 12-Level Secret Code Engine

Turn any message into a printable secret-code worksheet in seconds — 12 cipher levels from simple word shuffles right up to genuine RSA encryption.

Codemaker is a single self-contained HTML tool — no installation, no accounts, and no internet needed once it’s open — that turns any typed message into a coded worksheet at the click of a button. Twelve age-graded levels are built in: six transposition ciphers (Word Shuffle, Anagrams, Block Flip, Rectangle, Rail Fence, Keyed Columns) and six substitution ciphers (Reverse Alphabet/Atbash, Caesar Shift with a printable cipher wheel, Keyword Substitution, Vigenère, a Hill Cipher with matrix arithmetic mod 25, and a fully guided Simplified RSA level using genuine public-key cryptography with small, calculator-friendly numbers).

Every level generates a print-ready 3-part PDF automatically: Part 1 is the coded message, Part 2 is a fully worked step-by-step decoding worksheet (grids, cipher wheels, letter wheels or working boxes, depending on the level), and Part 3 is an answer sheet for quick marking. Export to A4, US Letter, or 6×9 for booklet-style printing.

Great for creating maths starters and plenaries, cryptography enrichment days, “murder mystery” challenges, Maths club puzzles, escape-room-style lessons, primary school transition events, riddles with coded answers, or cross-curricular links with computing — scaling all the way from a five-minute Year 5 warm-up to genuine RSA encryption for your top set or A-level Computer Science students.

The Detail

1. Word shuffle - just changes the order of the words
2. Anagrams - an anagram of each word in turn
3. Block flip - reverses the order of each block of (for example) 3 letters at a time and chunks the output into fixed length ‘words’
4. Rectangle - writes the message into the rectangle one way (across) and then reads them out the other way (downwards). The rectangle shape is customisable
5. Rail Fence - the classic shape-based zig-zag mix up
6. Keyed columns - Like Rectangle but the columns are read in a special order given by the keyword
7. Reverse Alphabet / Atbash - each letter is replaced by its partner in the reversed alphabet
8. Caesar shift - The alphabet is ‘wrapped round’ by a shift of n letters
9. Keyword substitution - the keyword determines the order of the substitution alphabet
10. The classic Vigenère Cipher - each letter has its own lookup table determined by the keyword and its position in the message
11. Hill Cipher - The step-by-step decoding sheet assumes no knowledge of matrix multiplication (by a (2x2) matrix) and explains it clearly, but the app also offers a tool for doing this. Very carefully guided to maximise success.
12. Simplified RSA using much smaller numbers

Installation
Runs entirely in the browser with no pupil data ever entered, stored, or uploaded anywhere — fully GDPR-compliant and safe on any school network. Works completely offline once opened. Full setup and troubleshooting guide included.