stillgrid.app

Stillgrid offers four sudoku variants: Classic, X-Sudoku, Jigsaw, and Killer. Each has its own rules page on the site, so you can read the rules before starting a puzzle. The site is mobile-first and requires JavaScript to play. The available material does not mention signup requirements or pricing, so treat access terms as unconfirmed until you open the site.

The four variants at a glance

Classic

This is the baseline: fill the grid so every row, column, and 3×3 box contains 1–9 once. If you already play sudoku elsewhere, this is the format you know. Stillgrid describes its difficulty as technique-graded, meaning puzzles are sorted by the solving techniques required rather than by how many clues are given. That matters if you want a puzzle that matches a specific technique you are practicing.

X-Sudoku

X-Sudoku adds one constraint to the classic grid: both long diagonals must also contain 1–9 exactly once. The practical effect is that cells on the diagonals carry extra restrictions, which can give you earlier placements and also create conflicts you would not see in Classic. If you are new to variants, this is usually the smallest step up from Classic because the grid layout stays the same.

Jigsaw

Jigsaw sudoku replaces the nine 3×3 boxes with nine irregular regions, often called jigsaw pieces. Each region still must contain 1–9 once, along with every row and column. Because region shapes differ from puzzle to puzzle, you cannot rely on memorized box patterns; you have to read the region outlines first. This variant rewards scanning region shapes before placing digits.

Killer

Killer sudoku adds cages: groups of cells marked with a target sum, and digits within a cage cannot repeat. You solve by combining those sums with row, column, and region constraints. The site also lists a Killer Sudoku Calculator, which suggests a tool for working with cage sums; the available material does not describe how it works, so check the page itself before relying on it.

How to choose a variant

• New to sudoku or want a clean baseline: start with Classic.
• Want a small twist without relearning the grid: try X-Sudoku.
• Want to break reliance on box patterns: play Jigsaw.
• Comfortable with arithmetic and want deeper deduction: try Killer.

A practical sequence is Classic first to confirm the interface, then X-Sudoku, then Jigsaw or Killer depending on whether you prefer shape-based or sum-based reasoning.

Other pages worth knowing

The site's page evidence also references a Daily Sudoku, an Archive, a Difficulty Grader, and an Evil Sudoku section. These are entry points rather than separate variants: the Daily and Archive give you puzzles to play, the Difficulty Grader relates to the technique-graded difficulty, and Evil Sudoku points to a harder tier. The material does not specify how each works, so open them directly if you want daily puzzles or a harder challenge.

Practical notes before you start

Stillgrid needs JavaScript enabled to play, so a browser with scripting blocked will show the page but not the puzzles. Each variant has an introduction page, which is the fastest way to confirm the exact rules the site uses, especially for Jigsaw region shapes and Killer cage rules.

Stillgrid offers a daily sudoku challenge and a separate archive page for past daily puzzles, and you can play without signing up. The site is a mobile-first sudoku destination with Classic, X-Sudoku, Jigsaw, and Killer variants, plus technique-graded difficulty and an "Evil Sudoku" level. To use the daily challenge or archive, you need JavaScript enabled, since the site states it requires JavaScript to play. The exact reset time for the daily puzzle, the number of archived days, and whether archive puzzles are grouped by variant are not specified in the available site information, so check the Daily Sudoku and Archive pages directly for those details.

What the daily challenge gives you

The daily challenge is a single sudoku puzzle intended to be played once per day, which makes it a natural fit for building a steady solving habit. Because Stillgrid grades difficulty by solving technique rather than only by how many clues are given, the daily puzzle's difficulty is set by the site rather than chosen by you. If you want to control difficulty instead, the main play pages and the Difficulty Grader are the places to look.

A practical routine looks like this:

1. Open the Stillgrid site with JavaScript enabled in your browser.
2. Go to the Daily Sudoku page.
3. Solve the puzzle for that day; no account or signup step is described.
4. Return the next day for the new puzzle.

The expected result is one fresh puzzle per day with no login friction. A common snag is a blank or non-loading board, which usually means JavaScript is blocked or the page has not finished loading.

How the archive works

The Archive page is the companion to the daily challenge: it lets you revisit past daily puzzles instead of losing them when the day rolls over. This is useful if you missed a day, want to replay a puzzle you enjoyed, or prefer to work through a backlog at your own pace.

Because the site description does not state an archive depth or a variant rotation for daily puzzles, treat those as things to confirm on the Archive page rather than assumptions.

Who this suits, and what to watch for

The daily-plus-archive setup suits players who want a low-commitment habit: one puzzle a day, with the safety net of catching up later. It also suits players who like switching between variants, since the same site hosts Classic, Killer, Jigsaw, and X-Sudoku, along with a Killer Sudoku Calculator and a Difficulty Grader for checking how hard a puzzle really is.

Two limits are worth knowing before you commit to the routine. First, everything depends on JavaScript, so the daily challenge and archive will not work in a browser setup that blocks scripts. Second, the available information does not describe notifications, streaks, or reminders, so if you want a daily habit, plan to bookmark the Daily Sudoku page yourself rather than relying on the site to prompt you.

The Killer Sudoku Calculator is a helper page on Stillgrid, a mobile-first sudoku site, for working out the number combinations that can fill a Killer Sudoku cage. It is a calculation aid, not a solver: you use it to check which sets of digits fit a cage's sum and size, then place those digits on the grid yourself. It is most useful when a cage is large or its sum is unusual, and least necessary for small two- or three-cell cages you can work out mentally.

What the tool is for

Killer Sudoku adds cages to the standard grid. Each cage is a group of cells marked with a total, and the digits inside must add up to that total while still obeying normal sudoku rules (no repeats in a row, column, or box). The hard part is often arithmetic rather than logic: which digits can sum to, say, 23 across five cells without repeating?

The calculator answers that question. You give it the cage's sum and the number of cells, and it returns the digit combinations that satisfy both. From there you eliminate options using the rest of the grid.

Where it sits on Stillgrid

Stillgrid describes itself as "sudoku, the quiet way" and offers several variants: Classic, Killer, Jigsaw, and X-Sudoku, plus a daily sudoku, an archive, a difficulty grader, and an Evil Sudoku section. The Killer Sudoku Calculator sits alongside these as a supporting page for the Killer variant rather than as a separate game.

That means the natural workflow is: open Killer Sudoku to play, and keep the calculator available in another tab or return to it when a cage stalls you. The site requires JavaScript to play, so the calculator and the puzzles both depend on it being enabled.

How to use it in practice

1. Identify the cage. Note its total and how many cells it covers. For example, a three-cell cage summing to 7.
2. Enter those two values into the calculator.
3. Read the returned combinations. For a three-cell cage summing to 7, the possible digit sets are limited, which immediately narrows what each cell can hold.
4. Cross-check against the grid. Remove any combination that repeats a digit already placed in the same row, column, or box, or that conflicts with a neighbouring cage.
5. Repeat as cages resolve. As digits get placed, earlier combinations drop away, and the remaining options often force a single answer.

When it helps most, and when to skip it

A useful habit is to treat the calculator as a check rather than a crutch: work out your candidate combinations first, then confirm them. That keeps the solving logic yours and uses the tool only to catch arithmetic slips.

Practical notes

• The calculator handles the combination arithmetic; it does not read your grid or suggest placements, so the deduction stays with you.
• Because Stillgrid is mobile-first, the page is usable on a phone, which suits playing Killer Sudoku on the same device.
• The site's other aids, such as the difficulty grader, are separate pages; the calculator is specific to Killer cages.
• No account is needed to use the site, per its description of being a no-signup sudoku site.

If you are new to the variant, start with a Classic puzzle to learn the grid, then move to Killer and keep the calculator open for the first few cages until the combination patterns become familiar.

Stillgrid grades difficulty by the solving techniques a puzzle requires, not by how many cells start empty. Its hardest tier is labeled "Evil Sudoku," and the site also exposes a "Difficulty Grader" entry point alongside its variant and daily pages. The practical takeaway: pick a level by the techniques you're comfortable with, and treat "Evil" as the top of that technique ladder rather than a separate game mode.

Technique-based grading, in plain terms

Most casual players assume a puzzle with 50 blank cells is harder than one with 35. That's a weak proxy. A grid with many blanks can still fall apart under basic scanning, while a grid with fewer blanks can stall unless you know a specific advanced pattern.

Technique grading works the other way around: a solver (or a grading routine) attempts the puzzle using a fixed order of methods, from simple to advanced, and records the most demanding method needed to finish it. The tier is then assigned by that ceiling.

What this means for you

• Low tiers are solvable with basic scanning and simple elimination — good for warm-ups or learning.
• Middle tiers typically require intermediate patterns that reward practice but don't demand deep study.
• High tiers (including Evil) require advanced techniques; a wrong guess usually means a long, messy recovery.

The benefit is predictability. Two puzzles in the same tier should demand roughly the same kind of thinking, even if their blank-cell counts differ.

Where Evil Sudoku sits

Evil Sudoku is Stillgrid's top difficulty label — the tier reserved for puzzles that resist the simpler technique set. It is not a variant; it's a difficulty band that applies to the standard grid. If you're new to the site, start below it and move up only when the current tier feels routine rather than lucky.

A useful self-check: if you finish a puzzle and can't explain why each step was forced, you're probably one tier too high. Drop back, and the technique gap becomes visible.

The Difficulty Grader

Stillgrid lists a "Difficulty Grader" page among its tools. The intended use is straightforward: bring a puzzle you already have (from a book, a newspaper, or another site) and see which technique tier it lands in. That lets you calibrate outside puzzles against Stillgrid's own scale instead of guessing from appearance.

Because the site requires JavaScript to run its puzzles, expect the grader to work in-browser rather than as a downloadable file.

Choosing your level

Two habits make the ladder work better. First, finish a tier without pencil-mark clutter before moving up — speed isn't the signal, certainty is. Second, when you get stuck, note which technique you were missing; that's the actual next rung, not simply "a harder puzzle."

A quick example of why cell count misleads

Suppose you compare two puzzles: one with 40 blanks that collapses under basic scanning, and one with 30 blanks that stalls until you spot an advanced pattern. By blank count, the first looks harder. By technique grading, the second is the harder puzzle — and it's the one that will actually cost you time. That gap is exactly what technique-based tiers are designed to close.

Bottom line

Stillgrid's difficulty scale is about what you must know, not how empty the grid looks. Evil Sudoku is the top of that scale, the Difficulty Grader lets you map outside puzzles onto it, and the right level for you is the one you can finish with reasoning you can explain afterward.

Stillgrid is a mobile-first sudoku website that offers Classic, X-Sudoku, Jigsaw, and Killer variants, with difficulty graded by solving technique, daily challenges, and no signup required. It suits players who want to open a browser and start a puzzle without creating an account, and who care about variant sudoku and technique-based difficulty rather than only a generic easy/medium/hard label. One practical condition: the site needs JavaScript enabled to play.

What you can play

The site also lists a Killer Sudoku Calculator, a Daily Sudoku, an archive, and a difficulty grader among its pages. The calculator is useful when you are stuck on cage sums; the grader is relevant if you want to understand why a puzzle is rated at a certain level.

How difficulty works

Stillgrid describes its difficulty as “technique-graded,” meaning puzzles are sorted by the solving techniques required rather than by how many givens they contain. In practice, that is a more meaningful signal: a puzzle with many clues can still require advanced techniques, while a sparse one may fall to simple scanning. The site also references an “Evil” tier, so expect a range that extends beyond beginner levels.

If you are choosing where to start, pick Classic first to learn the interface, then move to X-Sudoku (same grid, one extra rule) before Jigsaw or Killer, which change the board structure or add arithmetic.

Daily play and archives

The Daily Sudoku gives you a fresh puzzle on a regular cadence, and the archive lets you go back to earlier ones. This is the main reason to return to the site rather than use it once: a daily habit plus a backlog you can work through at your own pace.

Practical notes before you start

• JavaScript is required. The page states this directly; with scripting blocked, the puzzle area will not load.
• No signup is mentioned. The site describes itself as playable without registration, so you can start immediately. Nothing in the available material describes paid tiers or login-only content, so treat account or pricing details as unconfirmed rather than assuming everything is free forever.
• Mobile-first layout. The site is designed for phone screens first, which matters if you usually solve on a commute.
• Calculator as a helper. Use the Killer Sudoku Calculator to check cage combinations when a Killer puzzle stalls, rather than guessing sums.

Who it is for

Stillgrid fits players who already know basic sudoku rules and want variety without installing an app, and who prefer a calm, uncluttered presentation over timers, leaderboards, or account systems. If you need multiplayer competition, detailed stats tracking, or offline play, those features are not described in the available site material, so verify them on the site before committing.