Word Ladder
Transform START into END by changing one letter at a time. Each step must be a real word. 365 levels.
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How to play
- You're given a START word and an END word — same length.
- Type a new word that differs by exactly one letter from your last word.
- Every step must be a recognized English word.
- Continue building the chain until you reach END.
- Beat the reference solution length for the best score.
A short history
Lewis Carroll invented Word Ladder (he called it "Doublets") in 1877 and published it in Vanity Fair magazine. He called it "the most popular puzzle ever invented." Carroll used Word Ladder to demonstrate the idea of graph traversal long before computer science formalized it — every word is a node, every one-letter change is an edge.
Modern algorithms can find the shortest ladder between any two words in milliseconds using breadth-first search. Famous Carroll examples: HEAD → TAIL (5 steps), APE → MAN (5 steps), COLD → WARM (4 steps).
Strategy tips
- Work from both ends. Plan the last few steps from END backwards while planning forward from START.
- Common letter changes are easier. Vowel swaps (CAT → COT) and final-consonant swaps (CAR → CAT) often unlock more options than first-letter swaps.
- Don't backtrack. Words can't repeat in a single chain.
- Beat the reference. Our reference solution isn't always optimal — find a shorter chain for bragging rights.