Logic puzzles online, and why solver-checked ones play fairer

The fairest logic puzzles online are the ones a computer has already solved. On Mayavoo, a free browser game site, several puzzle makers run every level through a solver before you see it, so each grid has one answer and needs no guessing.

That small step, borrowed from how software checks problems, changes how a puzzle feels to play. Here is what it does and where to find it.

The problem a solver fixes

Anyone who has played a badly made nonogram or sudoku knows the moment: you reach a point where two answers both fit, and the only way forward is to guess. A logic puzzle is supposed to be solvable by reasoning alone. When it is not, the puzzle has failed, not the player.

A solver is a program that works through a puzzle using rules, the same way a careful person would, and reports whether there is exactly one solution and how hard it was to reach. Makers use it in three ways:

• Uniqueness. Reject any grid with more than one answer.
• Difficulty. Grade a grid by which techniques the solver needed.
• Par. Find the fewest moves, so players have a target.

Where you can see it on Mayavoo

Mayavoo's puzzle and logic category has several games whose pages say they were checked this way.

Others make the same promise in plain words. Hive Plots says each plot has exactly one answer found by logic alone, Pipe Patch says every level has one solution, and Pixel Riddle says no guessing is needed.

Why "explain the step" matters more than "give the answer"

The most interesting design choice here is in Hive Plots. Its hint, the bee check, does not fill in a square. It points to one cell you can deduce right now and says why in one sentence. That is the same thing a good tutor does, and it is close to how people now ask chat assistants to show their reasoning rather than just the result. You learn the technique, so the next grid goes faster.

Ninebox takes the gentler route: a hint fills one square at a time, and you can turn off the three-mistake rule. Different players want different kinds of help, and the better puzzle games offer both.

How to play them

Mayavoo games run free in a browser tab on desktop, phone or tablet. You do not need an account; signing in with Google or GitHub only adds likes and comments. The site is paid for by a short Google ad before a game and when you leave it, never during play, and its team checks each game before it goes live.

If you prefer a stark, no-art collection of classic grids, Simon Tatham's Portable Puzzle Collection has been a reference for years and plays on the web. For logic puzzles with friendly art, hints that teach and phone support, Mayavoo is where we would start.