Sudoku: game rules
Sudoku
🎯 Goal: Fill the grid so that every row, every column and each of the nine boxes holds each digit from 1 to 9 exactly once. Every puzzle has exactly one solution.
✏️ Playing: Pick a cell, then tap a digit or press the keys 1–9. With "Notes" (key N) you enter small candidates; they disappear by themselves when the digit is set nearby. "Undo" takes steps back, "Erase" (Backspace) clears the cell. The arrow keys walk the board. Solo you can pause: the clock stops and the board is covered.
💡 Help: Solo, the host can switch on "Mark mistakes at once": a wrong digit then gets a red frame. A hint fills the chosen empty cell correctly. If the board is full but not right, "Check" shows the wrong cells.
🏁 Race: With several players everyone gets the same puzzle. You only see the others' progress, never their digits. The board is only checked when you hand in a full one: wrong cells are marked and cost 30 seconds, and so does a hint. The fastest time including penalties wins; the race runs until everyone has finished or given up. Once somebody has solved it, the others only get the set extra time (5 minutes by default, can be switched off); after that the number of correctly filled cells decides the places. How often a hint is allowed is set by the lobby (default: one every 4 minutes).
🏆 Best time: For each variant and level (easy, medium, hard) your account keeps your fastest solve – solo and in a race alike. It only counts without help: no hint, no mistake marking, no submission with mistakes.
Settings & scoring
🧩 Variants: The host picks the variant and everyone solves the same puzzle; best times count per variant.
✖️ Diagonal X: Every digit also stands exactly once on each of the two long diagonals. The diagonal cells are tinted and carry a thin line.
🏯 Samurai: Five Sudokus share their corner boxes: a digit in a shared box counts for both grids. On a phone the board shows one grid; the map above it switches.
🧱 Jigsaw: Instead of the boxes there are nine irregular regions with a thick border – each holds every digit exactly once.
🔪 Killer: No givens: dashed cages show their sum in the top left corner, and no digit appears twice in a cage. The harder, the bigger the cages.
⚙ Settings: The host picks the level (Easy, Medium, Hard) and the variant; in a race also the extra time and how often a hint is allowed: free, three per game, one every 4 minutes or none.
🖱 Controls: Row, column and box of the selected cell are tinted, equal digits more strongly; below each digit key it says how often it is still missing. If a digit stands twice in a row, column or box, it is marked subtly – that does not count as help. In Samurai a large screen shows the whole board with digits and tools in the side column; on the phone the arrow keys lead into the neighbouring grid at the edge.
💡 Good to know: If the connection drops, a solo puzzle pauses by itself instead of being lost. A solution without help sets the best time in a race too.
🪑 With two players you face each other at a wooden table in the lobby: you always at the bottom, your opponent at the top, the game already laid out in the middle. An empty chair reads “Seat free” – you copy the invite link at the top next to the code.