DRYSTONE
A number puzzle that never runs out — every board built on your phone, graded by the thinking it actually takes.
Free to download · one £2.99 unlock · iOS 26.0 or later · no subscription, no account
Each block takes 1 to its size.
Never runs out
Puzzles are generated on your phone the moment you ask for one. No server, no download, no connection — and no end to them.
Difficulty that is honest
Graded by the hardest technique a solve actually forces, not by counting the given numbers. It is why other apps hand you an "expert" that plays like a warm-up.
Completely private
The app makes no network requests at all. There is no account, no sign-in, no analytics, and nothing to collect.
Suguru is two rules. Every block holds the numbers 1 up to however many squares it has, and no two identical numbers may touch — including diagonally. That second rule is the whole game: it is what turns a small grid into something worth thinking about.
Drystone builds each puzzle on your device and then checks it the way a person would, so a board labelled Expert is one that genuinely forces an expert technique — not one that simply hid more numbers. Nothing is fetched, so they never run out and they work on a plane.
Ask for a hint and it shows you the next logical step and the reasoning behind it, never just the answer. Pencil marks sweep themselves as you place numbers, and undo is lossless all the way back.
One daily puzzle is shared by everyone, derived from the date itself. It warms up on Monday and bites by Sunday, it keeps a streak, and it stays free whether or not you ever buy anything.
One payment, and that is the whole business model. Easy and Medium are free to play, and so is the daily. £2.99 unlocks Hard and Expert, unlimited puzzles and the hint engine.
No adverts on either side of that line. No subscription. No account, no sign-in, no email address. It unlocks on every device signed in to your Apple Account, and it is shareable with your family.
Why does every other Suguru app get harder by hiding numbers? Because counting givens is easy to implement and difficulty is not. Take away enough and a puzzle looks hard, but it may still fall to the same scan you used on the easy one — which is why their "expert" so often plays like a warm-up.
Drystone solves each puzzle the way a person would, then grades it by the hardest technique that solve actually forced. A board is Expert because it genuinely demands an expert's move, not because more squares are blank.
Simple rules. Endless moves.
Free to download, £2.99 to unlock everything. iOS 26.0 or later.