Master the Grid
Sudoku Skills: Master the Grid
Master the Grid
Sudoku Skills: Master the Grid
Learn the app workflow, board controls, walkthroughs, and Full Access tools.
You will learn: the fastest way to choose a puzzle, enter values, use notes, and review the logic behind each move.
Sudoku Skills is built as a tutor. You still do the solving, but the app can explain the reasoning behind each step, check your work, and help you practice Sudoku techniques in order.
Start from the Tools menu, choose a puzzle source, and click an editable cell. Normal entry places a firm value. Turn on Notes, or hold Shift while entering a digit, to work with candidate marks. In Notes entry, repeated presses cycle a candidate through Normal, Blue, Green, and Off so you can use manual coloring without leaving the board.
When you are unsure, use Validate to check the current board, Nudge for coaching, or Solve when you want the completed board and walkthrough. Full Access adds technique board animations inside supported walkthrough steps.
When you are signed in, replay the timeline after Solve. The strongest learning happens when you compare what you tried with the clean proof the walkthrough shows.
What to notice: The app is built around learning. Every action either helps you solve or helps you review how the puzzle was solved.
You will learn: where the setup actions live so the board can stay focused on solving.
The fixed header keeps navigation available without taking space from the board. Use the Tools menu for Puzzle Library, Sudoku School, Puzzle, Saved puzzles, Statistics, PDF Book, Sudoku OCR, Help, Account, and the platform-specific install action.
Access status now lives on the Account page instead of the header. Basic is the visitor demo experience with Beginner Random Puzzle and validation. Limited is the signed-in free experience with Daily Master the Grid Puzzle, the core solver, saved progress, Solve, Nudge, history, and stats. Registration only needs a verified email address and does not require payment information. Full is the monthly or annual membership tier for technique board animations, the curated Puzzle Library, Sudoku School, badges, the final Sudoku Skills Diploma badge, OCR, and printable PDF Books.
Install options adapt to the platform. Chromium browsers can show Install App. iOS shows Add to Home Screen instructions.
What to notice: Each Tools item opens its own focused application page. Puzzle returns to the active solving workspace; the other pages help you choose, learn, review, print, scan, or manage your account.
You will learn: how blank, Daily, random, curated, and saved sources differ.
Open Puzzle Library from the Tools menu. Basic visitors can start a Blank Puzzle or generate a Beginner Random Puzzle, and they can see the Daily account invitation. A free verified-email account gives Limited access to the Daily Master the Grid Puzzle, Intermediate through Expert random puzzles, Solve, Nudge, saving, history, and statistics. Full Access unlocks the curated Library with score-sorted cards, search by name or teaching focus, and difficulty filtering.
Curated Library, Daily, and School puzzles auto-track progress for signed-in users. They do not use the Save button because the app already knows their source. Blank and Random puzzles can be saved explicitly once you are signed in.
Daily Master the Grid Puzzles are personal assignments driven by your Daily progression. During the current app day, browser refreshes and ordinary status checks retrieve the same assignment and resume its account-backed progress. If the app date changes before you finish, meaningful work is preserved automatically in Saved Puzzles and the new day can still receive a fresh Daily on demand. Simply opening the old Daily without doing any work does not create a Saved Puzzle. The app displays the actual difficulty shown by the puzzle's reasoning path.
When a cached score is available, Library and School cards show two spoiler-safe numbers: Technique Score and Effort Score. The numbers help you choose a challenge without revealing the hardest technique or the solve path.
What to notice: Puzzle Library starts official puzzles and resumes official progress automatically. Saved puzzles is only for puzzle states you intentionally save to your personal account library.
You will learn: how the Daily is constructed, resumed, scored, and carried forward.
The Daily Master the Grid Puzzle is available with a free verified-email account. Its scheduled challenge level follows your Daily progression, and the puzzle card shows the actual difficulty, progress, and Technique and Effort scores when those scores are ready.
On page load, Sudoku Skills first checks whether you already have an assigned Daily. You may briefly see Checking your Daily Master the Grid Puzzle...; that is only a lookup. If no Daily is assigned and a new one is actually needed, the card changes to Constructing today's Daily Puzzle... while the rest of Sudoku Skills remains usable.
Your Daily progress is account-backed and resumes automatically. Refreshing the Puzzle page, opening the Library, or returning later retrieves the same assigned Daily board, progress, difficulty, Technique Score, and Effort Score. Refreshing never recalculates or replaces an existing Daily. If you explicitly chose Blank Puzzle instead, refresh keeps the Blank Puzzle workspace rather than replacing it with the Daily.
A Daily is stable for its assigned app day. Refreshing or reopening it on the same day resumes your saved progress. When the app date changes, a prior-day Daily with real progress is preserved automatically in Saved Puzzles so your work is not lost, while the new day's Daily remains available. A Daily that was only viewed creates no Saved Puzzle. Completed Dailies remain in your history and statistics.
What to notice: Checking and constructing are different states. Refreshing an existing Daily only checks and retrieves it. Expensive construction runs only when a new assignment is actually required.
You will learn: how Technique Score and Effort Score help you choose a puzzle without revealing the solving path.
Technique Score measures how advanced the required reasoning is on a 0 to 100 scale. A puzzle that requires a more sophisticated technique will not receive a Technique Score below the difficulty range appropriate for that reasoning. The app still keeps the hardest technique and solve path hidden before you solve.
Effort Score measures how much total solving work is expected on a 0 to 100 scale. It reflects the amount of work across the whole solve, so it can be high even when no single step is especially advanced.
Overall puzzle difficulty follows the stronger of Technique Score and Effort Score. That means a short puzzle with one demanding idea can still be Advanced or Expert, while a long puzzle with moderate techniques can also earn a higher difficulty through Effort.
Scores use green-to-red color bands as a quick visual guide, but the number is always shown too. They are selection aids based on the current Sudoku Skills scoring model, not spoilers for the solving path.
What to notice: A puzzle can have a high Technique Score but a lower Effort Score if it has one advanced move and a short finish, or a lower Technique Score with a higher Effort Score if it has many moderate steps.
You will learn: the board language used by Help, Nudge, School, and walkthroughs.
A Sudoku grid has 9 rows, 9 columns, and 9 boxes. Every row, column, and box must contain digits 1 through 9 exactly once.
Cells are named by row and column. R4C1 means row 4, column 1. Givens are the starting clues; they are locked and styled differently so you know they cannot be changed.
You do not need to memorize box numbers. The app shows coordinates when they help explain a move.
What to notice: Box numbers run left to right and top to bottom. R4C1 is the first cell in row 4 and belongs to box 4.
You will learn: how to use the board, number pad, keyboard, Clear, and Enter without muddying your recorded path.
Select an editable cell, then use the number pad or keyboard to enter a value. Use Clear, Backspace, or Delete to remove an editable value.
Press Enter to commit the current cell. This helps the manual replay record your final decision for that cell instead of every intermediate correction, then moves focus down one cell when possible.
On mobile, the same actions are available through larger touch targets. Timelines and recent lists are designed to scroll horizontally when space is tight.
What to notice: The number pad and keyboard do the same thing. Enter commits the selected cell, then moves focus down one cell when possible.
You will learn: how ordinary notes work, how Blue and Green coloring works, and what happens when a candidate is eliminated.
A candidate is a digit that can still legally fit in an empty cell. Notes keep those possibilities visible instead of forcing you to remember them.
Turn on the Notes pill for candidate entry. On a keyboard, you can also hold Shift while entering a digit to use Notes entry temporarily. The candidate itself remains on the board after Shift is released.
Each time you enter the same candidate in Notes entry, it cycles through Off -> Normal -> Blue -> Green -> Off. Normal is the ordinary small candidate mark. Blue and Green are the two manual Coloring states available for techniques such as Simple Coloring and for any relationship you want to track yourself.
Colored notes are still real candidates. If you enter a firm value that eliminates that digit from a peer, Sudoku Skills automatically removes the candidate and its color. Colored notes are saved with the puzzle and restored with your progress.
Manual Blue and Green notes belong to your solving state. They are separate from Assist highlighting and from temporary instructional colors used by walkthrough animations.
Try it: press any number repeatedly. The demo follows the real Notes cycle: Off, Normal, Blue, Green, then Off again.
You will learn: how to see the row, column, and box that constrain one cell.
Blue hatches are cell-focused. They mark every peer of the selected cell: same row, same column, and same 3x3 box.
Use Blue Assist when you are asking, "What numbers are ruled out for this cell?" It is especially helpful while learning candidates and singles.
If a red circle appears on a blue-hatched value, your selected value would immediately duplicate a peer.
What to notice: The blue hatches instantly reveal every cell that shares R7C9's row, column, or box. Those are the cells that can rule numbers out for R7C9.
You will learn: how to scan possible homes for one digit.
Yellow hatches are value-focused. They appear when the selected cell already has a number and show open peer cells affected by matching values elsewhere.
Use Yellow Assist when you are asking, "Where can this digit still go?" That question is the heart of hidden singles and many later techniques.
Yellow does not mean wrong. It means the selected value is being compared against the rows, columns, and boxes of matching values on the board.
What to notice: Yellow hatches show the selected cell's nearby row, column, and box cells that existing 9s block, including R7C8 and R7C9, which are affected through a matching 9's box.
You will learn: how the board shows an immediate rule violation.
Red circles mark copies of the selected number. When a red circle appears on a blue-hatched peer, the selected value duplicates a number in the same row, column, or box.
Use Red Assist as a quick visual warning. It tells you which existing value conflicts with the value you are trying to place.
For technique walkthroughs, the app no longer circles unrelated filled values in purple. Purple focus now points to the actual technique evidence.
What to notice: R7C1 is both blue-hatched and red-circled because it is in the same row as the selected cell and already contains 7. That red circle is the immediate warning that entering 7 in R7C9 violates the board.
You will learn: the difference between validation and a learning nudge.
Validate checks whether your current entries conflict with the known solution or with Sudoku rules. It is most useful for manual or imported puzzles where the app needs to confirm the givens and your entries.
Nudge is coaching. It uses the guided solving system to name a next logical idea, point to useful cells or candidate removals, and keep the final decision in your hands. Nudge and Solve require a free signed-in Limited account; Validate remains available to Basic visitors.
Use Nudge when you have stared at the board long enough that you are no longer learning. Use Solve when you want the completed board. Full Access adds board animations for supported solving steps.
What to notice: R4C1 should be 1. If 4 is entered there, Validate marks that exact cell red and leaves the givens alone.
What to notice: A correct manual entry is left alone. Validate focuses attention only on cells that need fixing.
What to notice: Nudge does not change the board. It names a human technique, explains what to look for, and points to the next placement or candidate elimination so your solve remains yours.
You will learn: how lessons, the Lesson Coach, the syllabus, progress, and badges fit together.
Sudoku School is a Full Access feature. Open it from Tools to see your progress, the next recommended lesson, the full course path, and the detailed syllabus.
Starting a lesson opens its teaching puzzle on the Puzzle page with the Lesson Coach. Read the objective, solve the board yourself, and reveal coach nudges only when you need them. For a technique lesson, the coach follows the lesson's actual technique: it tells you when prerequisite deductions still remain, then progressively narrows the relevant pattern and explains the proof without making the final candidate change or placement for you. Guided School lessons intentionally keep the focus on the lesson: regular Solve and Validate are not the shortcut for completing the exercise.
Lessons build from board foundations and candidate discipline through singles, locked candidates, pairs and triples, fish, wings, chains, uniqueness, What-If reasoning, and capstones. The curriculum stage tells you when a concept is taught; the Technique and Effort scores describe the difficulty of that particular teaching puzzle. Those two ideas can differ, so an Expert-stage concept can intentionally use an Advanced-rated grid when that makes the lesson clearer. Completing lesson groups earns in-app badges; finishing the School path earns the Sudoku Skills Diploma badge.
The syllabus is also useful when you are not in a lesson. It explains what each technique means, what evidence to look for, and how the technique connects to the rest of the course.
What to notice: School is designed for practice, not answer delivery. The coach keeps the lesson objective visible while you do the solving.
You will learn: how OCR review protects the puzzle before it reaches the board.
Choose Sudoku OCR from the header menu. The browser detects the grid and reads likely digits, then shows a review grid before anything is imported.
Correct uncertain or conflicting cells in the review grid. Validation then checks the reviewed givens for Sudoku consistency, enough clues, and a unique solution before the puzzle becomes playable.
Sudoku OCR is a Full access feature. The image-reading step is designed to speed up entry, not replace your review.
What to notice: Scan import is conservative. It speeds up entry, but the app asks you to confirm anything uncertain before the puzzle becomes a locked set of givens.
You will learn: when to use Print for the current board and when to use PDF Book for a larger practice set.
Use Print on the Puzzle page when you want a paper copy of the puzzle you are currently working with. The print view uses the active puzzle context rather than the surrounding application chrome.
PDF Book is a Full Access tool in the Tools menu for generating printable Sudoku practice books. Use it when you want a collection rather than a single active puzzle.
Printing does not change your live board. Account-backed progress and saved states continue to follow the puzzle separately.
What to notice: Print is about the active board; PDF Book is about creating a printable practice collection.
You will learn: how Solve turns a puzzle into named solving steps.
Solve completes the puzzle. For signed-in users, Solve opens a step-by-step walkthrough where each step names the technique, explains the reason, and highlights the cells or candidates that prove the move. Full Access adds board animations for supported solving steps.
For named techniques, use View Board Animation to watch the pattern play out on the board. You can play, pause, reset, or step frame by frame with the previous and next controls.
If you solve manually, Sudoku Skills records your committed entries and can replay your own path. When reviewing an earlier manual step during an active solve, use Rewind to Here to restore the live board to that point and continue from the cleaner branch. The rewind is recorded as one grouped replay step instead of many manual clears.
R4C1 has candidates 1, 4, and 8. But in box 4, only 1 can go in R4C1.
Technique: Hidden Single in a boxWhat to notice: The walkthrough title tells you the placement. The reason explains why that value is now safe.
You will learn: why expert puzzles sometimes require a controlled branch.
Strong solvers do not guess across the whole board. They choose a small uncertainty and follow its consequences.
The goal is to find a contradiction, a forced placement, or proof that a candidate can be removed.
This is still human reasoning. The guess is limited, tracked, and explained.
What to notice: The guess is limited and testable. The app records what happens so you can learn from the branch.
You will learn: how to explore a branch without damaging the real puzzle state.
What-If mode lets you ask, "What would happen if this candidate or combination were true?"
The app saves the decision board, follows the branch, and keeps the main solve safe.
Use What-If as a training gym for chains, contradictions, and capstone School lessons.
What to notice: Both cards show box 3 only. Purple cells are the values being tested in that combination, matching the live What-If cards.
You will learn: what gets saved manually, what auto-resumes, and what requires a connection.
Basic access is the visitor experience with Blank Puzzle, Beginner Random Puzzle, and validation. Limited access is the signed-in free experience with Daily Master the Grid Puzzle, the core solver, Intermediate through Expert random puzzles, Validate, Solve, Nudge, Save, Saved puzzles, history, and statistics. Creating that account only requires a verified email address. Full Access is the monthly or annual membership tier for technique board animations, the curated Puzzle Library, Sudoku School, badges, the final Sudoku Skills Diploma badge, PDF Book generation, and Sudoku OCR.
Use Save for Blank, imported, or Random puzzles you want to keep in your personal Saved puzzles library. School, curated Library, and Daily Master the Grid Puzzles auto-track progress and do not use the Save button.
The Puzzle page also keeps a local recovery draft for active non-Daily work. That includes an explicitly selected Blank Puzzle even before you type the first given, so refreshing the browser keeps you on the Blank Puzzle workspace instead of substituting an account puzzle.
When you refresh the Puzzle page, the Status card shows the recovery process while Sudoku Skills checks this device and your account. Once the source is known, it names the puzzle being restored so a temporarily empty board is never presented as an idle workspace.
Account saving normally happens quietly in the background. Sudoku Skills does not show routine messages such as syncing or synced while you solve. If the account copy of a puzzle is genuinely different from the copy on this device, the Status panel shows a warning that a newer account version exists and stops overwriting it. Your non-Daily work on this device remains available locally. Reopen the puzzle from Library, School, Saved puzzles, or History to continue from the account copy. Daily remains server-authoritative, so reopen a conflicted Daily from Daily.
When you explicitly log out, Sudoku Skills first preserves any eligible owner-bound local draft while your account identity is still known, then clears the visible account-backed puzzle from the board. That draft remains private to the same account on this device and cannot appear for another signed-in user.
Daily Master the Grid Puzzle resumes automatically from your account during its assigned app day. If the app date changes before completion, meaningful progress is preserved automatically as a Saved Puzzle before the fresh Daily is prepared. Merely viewing a Daily without making progress does not add anything to Saved Puzzles.
The installed app shell can load offline, but account actions, sync, Daily Master the Grid Puzzle, random generation, OCR validation, Nudge, Solve, and other server-backed actions require a connection.
What to notice: Save creates a personal Saved puzzles entry for puzzle sources that support manual saving. Official Library and School puzzles resume automatically without using Save. Daily resumes automatically during its assigned app day; if the day changes after you have made real progress, Sudoku Skills preserves that older Daily in Saved Puzzles automatically before the fresh Daily is prepared.
You will learn: how to use account history, streaks, difficulty trends, filters, resume, and review.
Statistics is available after you sign in. It summarizes completions, streaks, difficulty results, and recent puzzle history from your account-backed attempts.
Use the Status, Source, and Difficulty filters to narrow recent history. In-progress attempts can be continued. Completed attempts can open a saved walkthrough when replayable manual steps exist, or open a board review when they do not.
History records useful solving context such as elapsed time, nudges, validations, marked mistakes, and candidate-note counts. It is designed to help you notice your habits over time rather than turn Sudoku into a speed contest.
What to notice: Statistics connects account history back to the Puzzle page, so review and resume use the same board and metadata as the original attempt.
You will learn: the words used by Help, School, Nudge, walkthroughs, and board animations.
Each term below answers the same learning question: what is it, why does it matter, and how does Sudoku Skills show it? Full Access members can also use the Sudoku School syllabus for detailed technique-by-technique explanations.
Common beginner mistake: checking only a row or column and forgetting the box. Every placement must satisfy all three: row, column, and box.