What is Minesweeper?

Minesweeper is a classic single-player puzzle game where the player’s objective is to reveal all non-mine cells on a grid without triggering a mine. The game requires logic, deduction, and careful strategy.

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Game Overview

The game board is a 2D grid of hidden cells, some of which contain mines.
The player interacts with the board by clicking on cells.
If the revealed cell contains a mine, the game ends in a loss.
If the cell is safe, it reveals a number from 0 to 8 indicating how many of its adjacent cells contain mines.
If the number is 0, all adjacent cells are automatically revealed recursively.
The player can also flag a cell if they suspect it contains a mine.
The game ends in a win when all non-mine cells are revealed.

In this chapter, we’ll explore the low-level design of a Minesweeper game.

Lets start by clarifying the requirements:

1. Clarifying Requirements

Before starting the design, it's important to ask thoughtful questions to uncover hidden assumptions and better define the scope of the system.

Here is an example of how a conversation between the candidate and the interviewer might unfold:

Discussion

Candidate: "Should the game support different difficulty levels with preset board sizes and mine counts?"

Interviewer: "Yes, support at least three difficulty presets: easy (9x9, 10 mines), medium (16x16, 40 mines), and hard (30x16, 99 mines)."

Candidate: "What actions should a player be able to perform on a cell?"

Interviewer: "Players should be able to reveal a cell, flag a cell as suspected mine, or unflag a flagged cell."

Candidate: "Should the first cell the player clicks on always be safe, or can it contain a mine?"

Interviewer: "Good question. The first click should always be safe. It must never reveal a mine."

Candidate: "What happens when a player clicks on a cell with no adjacent mines? Should we auto-reveal surrounding cells?"

Interviewer: "Yes, if a cell has zero adjacent mines, the game should recursively reveal its neighbors until all non-mine cells with adjacent mines are found."

Candidate: "How do we determine game outcomes?"

Interviewer: "If a player reveals a mine → Game Over. If all non-mine cells are revealed → Player Wins."

Candidate: "Should the system track game statistics across multiple games, like win rate or games played?"

Interviewer: "Yes, tracking statistics would be a nice addition."

Candidate: "Is there a time limit on how fast the user completes the board?"

Interviewer: "You can ignore timer for this version."

Candidate: "Should we support undo functionality or saving and resuming the game?"

Interviewer: "Not in this version. We can discuss it if time permits"

Candidate: "Do we need to handle concurrent access, like a web-based version where multiple requests could hit the same game?"

Interviewer: "Think about it, but keep the focus on the core design. Thread safety is a bonus."

After gathering the details, we can summarize the key system requirements.

1.1 Functional Requirements

Support configurable board sizes and mine counts through difficulty presets (easy, medium, hard)
The first click is always safe (never a mine)
Revealing a cell with zero adjacent mines triggers a cascade reveal of neighboring cells
Players can flag and unflag cells to mark suspected mines
Flagged cells cannot be revealed until unflagged
The game detects a win when all non-mine cells are revealed
The game detects a loss when a mine is revealed
The system tracks statistics (games played, wins, losses) across multiple games

1.2 Non-Functional Requirements

The design should follow object-oriented principles with clear separation of concerns
The system should be modular and extensible to support future features
The code should be thread-safe for concurrent access
The components should be testable in isolation

2. Identifying Core Entities

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Design Minesweeper Game

Ashish Pratap Singh