Your first Classic puzzle
Alphadoku starts with a word or two-word phrase containing nine different letters. Spaces separate the words; they do not occupy cells. ALGORITHM, for example, supplies A, L, G, O, R, I, T, H and M.
The three Sudoku rules
Use every target letter exactly once in each row, each column and each bold 3×3 box. A repeated letter conflicts with the rules. Given letters are fixed; empty cells are yours to solve.
The extra rule: one hidden line
Exactly one row, read left to right, or one column, read top to bottom, spells the target in order. Other rows and columns contain the same letters in different orders. The hidden line is part of the puzzle’s logic—not a bonus unrelated to its solution.
If ALGORITHM is the target, its first letter must be A. A row beginning with a fixed M cannot be the hidden row. An empty first cell, however, does not rule the row out. Check all nine positions.
Choose your level
- Easy: the target line is shown, giving you a guided start.
- Medium: identify the hidden line. A correct choice fills it.
- Hard: Expert Deduction confirms the correct line, but you place its letters yourself.
- Pro: solve without revealing hints or automatic line fills.
Your controls
Select a cell, then a letter. The number below a letter says how many placements remain. Notes add pencil candidates rather than a final entry. Erase clears your own entry; Undo reverses a recent action. A hint reveals the selected empty cell in Easy–Hard. Use the line controls to consider or identify the target row or column.
The practice tutorial inside Classic walks through placing a letter and identifying a line. Settings contains credits and legal links. The technique reference is also available inside the game.
Leave and come back
Your current puzzle saves in this browser. Continue restores the board and notes. Starting a new free-play puzzle replaces that mode’s save after confirmation. Daily challenges use date-specific save slots. Private browsing, clearing storage, or switching devices can remove or separate progress.
Web play is unlimited. Revealing hints are free during the launch beta; Pro remains unassisted. There are no web purchases.