Simon Tatham's Portable Puzzle Collection

Here’s an uncomfortable question for the mobile games industry: if one open-source developer can give away forty puzzle games with infinite content and no monetization, what exactly are the rest of you charging for?

Simon Tatham is best known as the author of PuTTY, the SSH client that has quietly run half the world’s server administration for two decades. His Portable Puzzle Collection started in the early 2000s as a Windows and Unix side project with a simple thesis: every classic one-player logic puzzle should exist in a single, consistent framework, generated fresh on demand. Twenty-plus years later, that thesis has compounded into roughly 40 distinct games — Solo (sudoku), Pattern (nonograms), Mines (minesweeper), Loopy (slitherlink), Bridges, Net, Untangle, Galaxies, Light Up, Towers, Slant, Tents, Keen, Signpost, and a long tail of originals most players have never heard of.

The mobile versions are community ports done right: Greg Hewgill maintains the iOS build, Chris Boyle the Android one, and both layer touch-native conveniences — pinch-to-zoom, on-screen arrow keys, night mode — over Tatham’s battle-tested puzzle engines. The reception is strong by app-store standards: 4.8 out of 5 from 242 ratings.

Market positioning is almost a category error here. This collection doesn’t compete with the Candy Crush economy; it repudiates it. No ads. No in-app purchases. No data collection. Fully offline. In a storefront built on interrupting you, this is software that simply leaves you alone with your own brain. That’s rarer than it should be, and it’s the single most important fact about this product.

• ~40 games, one engine: Sudoku, nonograms, minesweeper, slitherlink, hashiwokakero, and dozens more — including genuine originals — all sharing consistent controls, menus, and save behavior.
• Algorithmic generation with a solvability guarantee: Every puzzle is generated on-device and verified solvable by logic. The design means no broken grids and no running out. This is the collection’s killer feature.
• Adjustable everything: Grid size and difficulty are parameters, not paywalls. A 9×9 Easy Solo and a 16×16 Extreme one live in the same menu.
• Respectful quality-of-life tooling: Unlimited undo/redo, mid-game saves, session persistence, and an instant Solve button for when you’d rather learn than grind.
• Zero-extraction business model: Free, open-source, offline, ad-free, tracker-free. The entire monetization strategy is that there isn’t one.

The Generation Engine Is the Whole Game

Most puzzle apps are content treadmills. Someone hand-authors (or licenses) 500 grids, gates them behind an energy meter, and sells you pack six when you finish pack five. Tatham’s collection replaces that supply chain with mathematics. Each game ships with a generator and a solver; the generator proposes a puzzle, the solver proves it’s solvable through deduction alone, and only then does it appear. The practical consequence is profound: the content never ends, and it never cheats. When a Loopy grid at Hard difficulty stumps you, the fault is yours — the app has already verified a logical path exists. That guarantee changes your relationship with difficulty. You stop suspecting the puzzle and start interrogating your own reasoning, which is the entire point of logic puzzles.

The difficulty tuning deserves specific praise. These aren’t vague “easy/medium/hard” labels slapped on random grids. The generators target the deductive techniques required: an Easy Solo needs only basic scanning; an Extreme one demands chained inferences that will humble sudoku veterans. That’s the difference between a difficulty slider and a curriculum. Played seriously, this collection teaches you to think in each puzzle’s native logic, one technique tier at a time.

The Loop: Two Minutes or Two Hours

The session design is honest in a way modern mobile games refuse to be. There’s no daily streak nagging you, no lives system rationing your attention, no push notification pretending your puzzles miss you. You open the app, you’re exactly where you left off — mid-grid, mid-thought — and you leave whenever you like. A small Tents grid is a 90-second palate cleanser; a large Pattern board is a full evening. The collection scales to your attention instead of harvesting it.

The Solve button is the most philosophically interesting control here. Conventional design wisdom says never let players skip the challenge. Tatham’s collection shrugs and hands you the answer, and it turns out that’s the right call for this audience. Studying the solved state of a Slant or Galaxies grid you were stuck on is a legitimate learning tool — you reverse-engineer the deduction you missed. It treats players like adults who own their own time. More games should.

Where the Seams Show

Fairness requires saying this plainly: the collection has real friction, and it’s concentrated in discoverability and touch precision. There is no onboarding to speak of. Each game has documentation, but the app makes little effort to teach; a first encounter with Net or Signpost is a cold plunge, and it’s easy to imagine a meaningful share of downloads never getting past the initial “what am I even looking at” wall on the more obscure entries. A stingy in-context hint system — not a full solver, just a nudge — would transform the on-ramp for newcomers.

And on a 6-inch phone screen, grid-dense puzzles get fiddly. A 16×16 Solo or a large Loopy board demands constant pinch-zooming, and fat-finger errors creep in at the exact moment concentration matters most. Unlimited undo blunts the pain but doesn’t eliminate it. These puzzles were born on desktops with mice, and at high densities, the touch layer — capable as it is — can’t fully hide that ancestry.

Let’s not sugarcoat it: this collection looks like a computer science department, because it is one. Flat colors, thin lines, system-adjacent typography, four screenshots on the Play Store because honestly, what would a fifth show? There’s no juice — no particle burst when you crack a grid, no satisfying thunk on placement, none of the sensory reward layer that studios like Zach Gage build entire games around. Calling the visuals “bare-bones” is being polite. If aesthetics are a primary reason you play puzzle games, this app will read as austere to the point of hostile.

But the austerity is load-bearing. Every pixel encodes puzzle state; nothing animates that doesn’t need to. And the design pays off on the technical side: a 2D collection of this scope is light on hardware, so it should run comfortably on anything from a current flagship to a years-old phone. Night mode on both platforms is genuinely well-executed for late-night solving. There’s a lesson in that, even if the wish remains that someone would give these games one coat of paint.

Android (Chris Boyle’s port) is the more feature-complete mobile build. The on-screen arrow-key overlay is an elegant answer to the precision problem — coarse positioning by touch, fine adjustment by virtual d-pad — and keyboard support means the app should be quietly excellent on a Chromebook or with a folding keyboard. Long-press context actions are sensibly mapped per game.

iOS (Greg Hewgill’s port) is leaner but polished where it counts: pinch-to-zoom, state restoration, and a layout that feels at home on iPhone. It’s the slightly quieter sibling — fewer power-user affordances than the Android build — but the core experience is identical, and on an iPad the collection is arguably at its best on any platform: enough screen real estate that even dense grids stop fighting your fingertips.

On both platforms, note what’s absent: no iCloud/Google sync between devices, no completion statistics, no achievements. Progress persists per-device and that’s it. Purists won’t care. Anyone who bounces between a phone and a tablet will notice.

Simon Tatham’s Portable Puzzle Collection is the rare piece of software that gets more impressive the longer you think about the economics. One developer’s twenty-year side project, ported by volunteers, delivers more durable entertainment than a storefront full of extraction-engine puzzle apps — and asks for nothing back. Its flaws are real and worth naming: it’s visually indifferent, pedagogically lazy, and occasionally cramped on a phone. But those are blemishes on something substantial. Judged on the axes that matter for a puzzle collection — depth, fairness, longevity, respect for the player — this earns a clear recommendation, with reservations that stop short of greatness. Download it, learn three games, and check back in five years. It’ll still be there, still free, still generating.