GridSum Game

A Sudoku-like number puzzle game where players must select cells in a grid to match target sums for each row and column.

Game Rules

The game board is a square grid of size NxN (where N is between 3 and 9)
Each cell contains a number between 1 and 9
Players must select cells in each row and column to match the target sums
A cell can be selected or deselected
The game is won when the sum of selected cells in each row and column matches their respective target sums

Difficulty Levels

The game offers four difficulty levels:

Easy:
- Each row and column has only one possible combination to reach the target sum
- Target sums are achieved by selecting a single cell or a small number of cells
- Perfect for beginners
Medium:
- Each row and column has 2-3 possible combinations to reach the target sum
- Target sums require selecting multiple cells
- Good for players who understand the basic mechanics
Hard:
- Each row and column has 3-5 possible combinations to reach the target sum
- Target sums require selecting multiple cells with overlapping possibilities
- Challenging for experienced players
Very Hard:
- Each row and column has 5+ possible combinations to reach the target sum
- Target sums require selecting multiple cells with many overlapping possibilities
- For expert players seeking maximum challenge

API Endpoints

Get New Game Board

GET /game/{size}/{difficulty}

Parameters:

size: Board size (3-9)
difficulty: Difficulty level (easy, medium, hard, very-hard)

Response:

{
  "board": [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
  ],
  "targetRowSums": [6, 15, 24],
  "targetColSums": [12, 15, 18],
  "boardSize": 3,
  "difficulty": "medium"
}

API Usage Examples

Starting the Server

go run main.go

The server will start on port 8080 by default.

API Examples

Create a new 3x3 easy game:

curl http://localhost:8080/game/3/easy

Create a new 5x5 medium game:

curl http://localhost:8080/game/5/medium

Create a new 9x9 very hard game:

curl http://localhost:8080/game/9/very-hard

Example Response

{
  "board": [
    [7, 4, 2, 8, 1],
    [3, 9, 5, 6, 4],
    [8, 2, 7, 1, 9],
    [5, 1, 4, 3, 7],
    [2, 6, 9, 5, 8]
  ],
  "targetRowSums": [15, 18, 16, 13, 20],
  "targetColSums": [17, 16, 18, 14, 17],
  "boardSize": 5,
  "difficulty": "medium"
}

Error Responses

Invalid board size:

{
  "error": "Invalid board size. Size must be between 3 and 9"
}

Invalid difficulty level:

{
  "error": "Invalid difficulty level. Must be one of: easy, medium, hard, very-hard"
}

Game Flow

Request a new game board using the API
Present the board to the player
Let the player select/deselect cells
Calculate sums for each row and column
Compare with target sums to check if the solution is correct

Notes

The server handles requests concurrently
Each request generates a unique board
All generated boards are guaranteed to have at least one valid solution
Target sums are always achievable using the numbers in the grid
The API response includes all necessary information to play the game

Performance Requirements

Board generation time should be under 100ms
Solution validation time should be under 100ms
The game must have at least one valid solution
Target sums must be achievable using the numbers in the grid

mstgnz/gridsum