Co-authors and circles
Private circles for family and friends. Times only, never the numbers, and only once you have proven the same lemma.
A daily Sudoku for iPhone
One 6x6 Sudoku a day.
Free. No ads, ever. For iPhone.
One 6x6 Sudoku a day.
The same one for everyone.
Two to six minutes. Prove it, see where you rank tonight, and beat your people in private circles. Free forever.
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Lemma #2141:42Proven
Open to everyone Saturday 31 October
- Free forever
- No ads, ever
- No account needed
- Same puzzle worldwide
- Made in Bucharest
Try a lemma
Prove a small one right here.
Seven cells are open. Pick a cell, pick a number. Stuck? Ask for a hint: it names the rule, and it never fills the cell for you.
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This board comes alive with JavaScript turned on. The real lemma is in the app, new at midnight your time.
Use the arrow keys or tap a cell, then press 1 to 6.
Proven
0:00
The real one is in the app, new at midnight your time.
How it works
Three steps. No energy bar.
- Open the daily lemmaEveryone on Earth gets the same puzzle on their own date. No levels to grind, no waiting.
- Prove itPure logic, a hint that shows its reasoning when you are stuck, and your rank among tonight's solvers when you finish.
- Share the proof, not the numbersA share card shows your time and the order of your proof. Nobody sees a digit, so nobody is spoiled.
What you get
A small ritual, built with care.
Your sequence and the freeze
Prove a lemma every day and the sequence grows. A freeze saves the day you miss.
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Hints that explain
A hint names the rule and the cell. It never fills it, so you see the move next time.
Theorems
Every 36 proven lemmas make a theorem in your name. Each one uncovers a hidden figure and gives you a reward.
Global rank
See where your proof lands among everyone who proved tonight's lemma.
Faster than 99% of tonight's solvers
Paper by day, chalkboard by night
The app follows your phone. A white sheet in the morning, a quiet chalkboard after dark, both drawn by hand.
The screens
Seven screens, one small proof a day.
Lemma Plus
One a day not enough? Play thousands.
Corollaries are fresh lemmas made on your phone, at the difficulty you pick. They never run out. The archive opens every daily lemma you missed.
Free
$0 forever
- The daily lemma, every day
- Circles and your global rank
- The share card
- Your sequence and freezes
- Theorems
Lemma Plus
- Yearly$19.99 a year7 days free
- Monthly$2.99 a month
- Family$29.99 a year7 days freeFamily Sharing, up to 6 people
- Unlimited corollaries: easy, medium, hard, expert
- The archive: every past daily lemma
- Every ink, paper and app icon
Cancel any time in Settings.
Questions
Good questions.
What is a lemma?
A lemma is a puzzle: one 6x6 Sudoku. The daily lemma is the one everyone plays on their own date. Solve it and you have proven it.
Why 6x6?
It fits a pause. A 6x6 board with 2 by 3 boxes takes two to six minutes and still rewards real logic. Every lemma can be proven without guessing. Read the rules.
When does the new lemma arrive?
At midnight, your local time. Everyone plays the same lemma on their own date; the countdown at the top of this page runs to your midnight.
Is it really free?
Yes. The daily lemma, circles, rank, the share card, your sequence and your theorems are free forever, with no ads. Lemma Plus is optional: more lemmas and the archive.
Do I need an account?
No. Open the app and play. Sign in with Apple is optional, for backing up your notebook and for circles.
What if I miss a day?
A freeze saves your sequence on a day you miss, so one busy day does not break it. Your notebook shows how many freezes you hold.
Who sees my times?
Only your co-authors, in the circles you share with them, and only after they have proven the same lemma. The global rank shows no names unless you turn that on.
What do you keep about me?
Very little: a random player ID, your solves and progress, and your circles. No ads and no trackers. The details are in the privacy policy.
Does it work on iPad?
Lemma is an iPhone app for now. It runs on iPad in iPhone mode, and an iPad layout comes later.
Is there an Android version?
Not at the moment. Lemma is for iPhone.
How do I cancel Plus?
In Lemma's Settings under Manage subscription, or in your iPhone's Settings under your name. Steps are on the support page.
A small proof, every day.
Open to everyone Saturday 31 October
Free. No ads, ever. For iPhone.