How to play Lumesweep: reveal, flag, and chord a logic minesweeper

Lumesweep is a free, no-account logic puzzle you play in your browser. It plays like classic minesweeper — clear every safe square without detonating a mine — but every board is verified solvable by pure logic first, so you never lose to an unavoidable 50/50 guess.

What is Lumesweep?

Lumesweep is a browser-based minesweeper-style puzzle. You are shown a grid of covered tiles hiding a fixed number of mines. Reveal a tile and it shows either a mine (you lose) or a number counting the mines in the eight tiles around it. Read those numbers, deduce where the mines are, flag them, and clear every safe tile to win. There are three classic sizes: Beginner (9×9, 10 mines), Intermediate (16×16, 40 mines) and Expert (30×16, 99 mines). It is free, runs entirely in your browser, and needs no download or sign-up.

How to play, step by step

1. Reveal a tile by tapping or left-clicking it. Your very first tap is always safe and always opens a wide cascade of tiles, giving you a foothold.
2. Read the numbers. A “3” means exactly three of that tile’s neighbours are mines. A blank (zero) tile has no mines nearby, so its neighbours open automatically in a cascade.
3. Flag a suspected mine by long-pressing it on touch, or right-clicking on a mouse. The mine counter tracks how many flags you have left to place.
4. Chord to sweep quickly: once a revealed number has that many flags around it, tap the number (or double-click it) to reveal all its remaining neighbours at once. If a flag is wrong, chording reveals a mine — so only chord when you are sure.
5. Win by revealing every non-mine tile. Your time, 3BV and win streak appear on a shareable card.

Prefer the keyboard? Arrow keys move a cursor, Space or Enter reveals, F flags, C chords, R restarts, and 1/2/3 switch difficulty. The grid is fully screen-reader labelled.

Tips to get faster

• Work the edges of opened areas first — the numbers there give you the most information.
• Learn the 1-2-1 and 1-2-2-1 patterns along walls; they resolve to fixed mine positions without any counting.
• Flag only when a flag helps you chord. Over-flagging slows you down; strong players flag sparingly and chord a lot.
• Chording is where speed comes from. A single chord can open a dozen tiles at once.
• When a number equals the count of covered neighbours, all of those neighbours are mines. When its flags already equal its number, every other neighbour is safe.
• Because Lumesweep boards are always solvable, if you feel stuck, the logic is there — slow down and re-read the border numbers instead of guessing.

What does “no-guess” mean?

In ordinary minesweeper you sometimes reach a position where two tiles are equally likely to be a mine and no amount of logic can tell them apart — a 50/50 that ends good runs by luck. Lumesweep removes those. When a board is generated, a deductive solver plays it using only the information a human can see and confirms the whole board can be cleared with forced moves alone. Only boards that pass carry the NO-GUESS ✓ badge on the result card. Every win is earned by reading the numbers, not by gambling.

What is 3BV?

3BV (the “Bechtel Board Benchmark Value”) is the minimum number of left-clicks needed to clear a board if you played it perfectly, using cascades and chords optimally. It is a measure of how much work a board actually contains, which is why the speed-running community ranks boards and runs by 3BV rather than raw time. Lumesweep shows the 3BV of each board you clear on its result card, so you can compare like with like.

FAQ

Is it free? Yes. Lumesweep is free and ad-supported.

Do I need an account? No. There is no sign-up and no login. Your best times and win streak are saved locally in your own browser.

Does it work offline? The game itself runs entirely in your browser with no server calls, so once the page has loaded it keeps playing without a connection.

Can I replay a friend’s exact board? Yes. Sharing a result includes a board link so anyone can open the identical board and try to beat your time.

Is it really always solvable? Every board marked no-guess has been verified solvable by logic alone before you ever see it.