What is VENO PrismNine?
VENO PrismNine is a free 3D Sudoku you play in your browser. The board is made of ceramic tiles and frosted glass resting on a sunlit morning desk; every move makes a small, clean tap, and every finished box lights up a shard of the prism. The reward is not speed or flashy effects but the quiet “aha, of course!” moment when a digit has only one place left to go.
How to play
It is classic Sudoku: fill a 9×9 grid so that every row, every column and every 3×3 box contains the digits 1 to 9 exactly once. The given digits cannot be changed. Tap a cell, then tap a number on the 1–9 keypad — or switch to digit-first and pick the number before the cells. On a keyboard, the arrow keys move between cells, 1–9 places a digit, Backspace clears it, N toggles notes and Ctrl+Z undoes.
Notes, undo and gentle checking
Pencil in candidates with the Notes button; when you place a digit, the same number can be cleared from the notes of related cells automatically. By default the game only marks digits that clash in the same row, column or box — it never secretly colours your numbers right or wrong. If you want, you can ask for a full check. There are no lives: make a mistake, fix it, undo or redo, and keep going.
A Coach that explains why
Stuck? The Coach highlights the area worth looking at and explains the reasoning from your current board — for example, why a digit has only one possible cell in a group. You can place the number yourself or let the Coach apply exactly one step. It never fills a chain of answers behind your back. Learn mode turns these ideas into short lessons: the rules, notes, singles, locked candidates and pairs.
Modes and difficulty
Classic lets you choose Easy, Standard or Advanced and play with no time limit. Daily serves one puzzle per UTC day, the same for everyone. Journey moves through chapters that gradually introduce new techniques and unlock cosmetic themes such as Paper Sunday next to the default Prism Desk. Every released puzzle has exactly one solution, and difficulty is rated by the reasoning it needs, not just by how many cells are empty.
On phone and desktop
On a wide screen the board sits on the left with the keypad and tools on the right. On a phone the board stays a clean square with a large 1–9 keypad underneath, sized for thumbs. There is no account and nothing to install; settings and your current game are saved in your browser.
Play VENO PrismNine free
Open a fresh grid, take a breath and find the one digit that has nowhere else to go.