Size Sets the Length, Density Sets the Difficulty
A custom board has three numbers, but they do different jobs. Width and height decide how long a game lasts and how much of it you can see at once. The mine count only means something relative to the size, so the number to watch is density: mines divided by cells. A 30x30 board with 90 mines is a long, gentle game at 10%; the same board with 200 mines is a long, punishing one at about 22%. The form under the inputs works out the density for you before you start.
The classic boards make good reference points, because most players already know how they feel:
| Board | Grid | Mines | Density |
|---|---|---|---|
| Beginner | 9x9 | 10 | 12.3% |
| Intermediate | 16x16 | 40 | 15.6% |
| Expert | 30x16 | 99 | 20.6% |
What Each Density Feels Like
Density changes the character of a game more than size does. These bands are a guide rather than exact borders, and luck in the layout moves any single board up or down a little:
| Density | How it plays |
|---|---|
| Under 10% | Very open. Most clicks cascade, and the board is more about tidying up than deducing. Good for learning on a big board or for a relaxed marathon. |
| 10 to 15% | Beginner territory. Large openings, short frontiers, and almost everything can be solved by the two basic rules. |
| 15 to 18% | Intermediate feel. Openings shrink and you start managing several separate fronts at once. |
| 18 to 22% | Expert feel. Small first openings, long borders, and an occasional forced guess near the end. |
| 22 to 28% | Hard. The first click often opens only a small patch, and forced guesses become a regular part of the game. |
| 28 to 35% | Extreme. Many boards cannot be finished without several guesses. Fun as an experiment, frustrating as a habit. |
The form caps mines at 35% of the cells and always leaves at least nine cells free, because your first click and its neighbours are kept clear of mines on every custom board. Above roughly 22%, more and more positions come down to a choice between cells that no visible number can tell apart. Custom boards are dealt at random, so they can contain those forced guesses. If you want pure logic, tick No-guess board in the form (up to 22% density), or play the no-guess Minesweeper boards, where every layout has been checked by a solver.
Small, Wide, Tall and Huge Boards
Small boards (5x5 to 8x8) finish in seconds but are unforgiving: the safe opening takes up a large share of the grid, and with only a few numbers on the board, a dense small board often ends in a guess. Keep them under about 15% for a fair puzzle.
Rectangles are worth trying. Expert is 30 wide and 16 tall because it was designed for a landscape monitor. On a phone held upright, a tall, narrow board such as 10x30 uses the screen far better than a square one, and on a wide desktop monitor something like 40x20 fills the width without scrolling.
Huge boards (40x40 and up) are marathons. A 50x50 grid has 2,500 cells, more than five times Expert's 480. Keep density moderate, somewhere around 15 to 18%, unless you enjoy losing a long game to one late guess. On boards this large, chording matters more than anywhere else: flag a number's mines, then click the number (or hover and press Space) to open everything around it at once. The Minesweeper pattern atlas helps here too, since recognising a 1-2-1 at a glance saves real time over thousands of cells.
Custom Boards on Phones and Tablets
Cells shrink to fit the screen, down to a minimum size that still leaves them easy to tap. On a typical phone held upright, that means roughly 12 to 14 columns fit across. Wider boards scroll sideways inside the game frame, and tall boards scroll within a frame that takes up most of the screen height. Drag to scroll: a finger that moves is treated as scrolling, never as a tap, so you will not reveal a cell by accident. Long-press flags a cell, and the Dig / Flag switch under the board lets each tap place a flag instead.
Custom games are for practice and fun: they are not added to your best times, which only cover the three classic difficulties. Use the smiley to deal a new board with the same settings, or Change Settings to go back to the form.