Minesweeper Bomb Generation And Tile Revealing

When I was creating a little Minesweeper game, I got confused at some points. My bomb generation didn’t look quite right, and I for sure didn’t quite get the whole cascading tile reveal thing. With a bit of internet research, I found what I was looking for. I’ll explain it all in one place for my own research purposes.

Bomb Generation

When I started this project I attempted to use a random bomb generator. By this I mean on each square, before it gets generated, give it a one in 15 change of being a bomb. Personally, I’m not sure why this never looked right. Something about the layout of the bombs did not mimic the classic Minesweeper game.

After looking at some open source Minesweeper examples, I started to get the idea. I wrote some mathematical statements describing the generation of bombs and how to get their x,y position from an appropriate number. For those non-mathy people, don’t leave just yet; there will be code equivalents to the math.

W and H are the width and height of the board respectively.

0rW×H \it 0 \leq r \leq \text W \times \text H x=rmodW \it x = r \bmod \text W y=rH \it y = \left\lfloor\frac{r}{\text H}\right\rfloor

The code equivalent to this in Python is below:

import random
# r <= 0 <= W*H
r = random.randint(1, W*H)-1

# x = r mod W
x = r % W

# y = floor(r/H); note the special syntax python has for this operation
y = r // H

So that’s that, we can put this in a big ‘ol for loop and generate an arbitrary n number of bombs given a width and height of a Minesweeper board.

Cascading Tile Revealing

This one is hard to describe; I am adapting this from leetcode.com. Whenever a player clicks a tile, the following logic should be used:

  1. If a mine is revealed, the game is over. (obviously)
  2. If a tile with no adjacent mines is revealed, recursively reveal all eight adjacent tiles.
  3. If a tile with one or more adjacent mines is revealed, display the number of mines next to it.

Here is the code in Python for this algorithm.

def reveal_square(x, y, board, alread_revealed):
  # if already checked
  if (x, y) in already_revealed:
  # if it's a bomb
  if board[x][y] == 'B':
  # if the bomb number is more than 0
  already_revealed.append((nx, ny))

  # from -1 to 1
  for xd in range(-1, 2):
    for yd in range(-1, 2):
      # skip if it is this the center tile
      if x+xd == x and y+yd == y:
      # recursively check the adjacent square
      reveal(x+xd, y+yd, board, already_revealed)
  return already_revealed

This has no checks for valid squares, but it’s the general idea. This function returns an array of tile coordinates which should be revealed.


I wrote this because in the first place because I was writing my own Minesweeper game. I hope that this helps you with getting the general idea of a Minesweeper game. The completed version of this game is available on my lamegames site. Let me know what you think!

Happy hacking!