A multiplayer puzzle and board game platform for Android.
Real-time online matches, ranked leagues, AI opponents, daily challenges, and an in-game economy — all in one app. Built with Jetpack Compose and Firebase Realtime Database.
Sudoku — Classic 9x9 and Killer Sudoku. Four difficulty tiers: Easy, Medium, Hard, Expert. Cooperative and competitive multiplayer modes.
TicTacToe — Three board sizes (3x3, 5x5, 7x7), Bomb Mode, and Ultimate TicTacToe. Online or against a minimax AI with opening book and transposition table.
Dame (Checkers) — Full checkers rules with forced captures and king promotion. Online or against AI.
Muhle (Nine Men's Morris) — Endgame-accurate AI with perfect play in 3-piece scenarios.
All games use Firebase Realtime Database for sub-second state sync. Players join via six-character room codes or public matchmaking.
- Private rooms with shareable codes
- Public matchmaking queue with difficulty and mode filtering
- Real-time opponent progress tracking
- Cooperative and competitive Sudoku modes
- Automatic room cleanup on disconnect
- League system with seven ranks and seasonal leaderboards
- Friends list with in-app challenges and activity feed
- Daily challenges with rotating puzzle seeds
- Daily login bonus and lootbox rewards
- In-game coin economy with a theme shop
- 50+ achievements with cross-session persistence
- Detailed statistics dashboard per game type
- Puzzle editor for custom Sudoku layouts
- Intelligent hint system with ad-based bonus hints
- Offline single-player with auto-save and resume
| Layer | Technology |
|---|---|
| UI | Jetpack Compose, Material Design 3 |
| State | ViewModel + StateFlow |
| Backend | Firebase Realtime Database, Firebase Auth |
| Local storage | Room (SQLite) |
| Build | Gradle with Kotlin DSL, KSP |
| Min SDK | Android 8.0 (API 26) |
| Target SDK | Android 15 (API 35) |
app/src/main/java/de/sudokuonline/app/
data/
model/ Data classes — GameRoom, Player, SudokuBoard, TicTacToe/Dame/Muhle models
repository/ Firebase repositories — Game, TicTacToe, Dame, Auth, Friends, Leaderboard
local/ Room database — game history, AI position cache
game/
SudokuGenerator.kt Backtracking puzzle generator with difficulty control
SudokuSolver.kt Constraint propagation solver
SudokuValidator.kt Move validation and completion checks
KillerSudokuGenerator.kt
TicTacToeLogic.kt / DameLogic.kt / MuhleLogic.kt
ai/
AIEngine.kt Minimax with alpha-beta pruning
TranspositionTable.kt Zobrist-hashed move cache
ThreatSpaceSearch.kt Threat-based pruning for TicTacToe
OpeningBook.kt Precomputed opening positions
MuhleEndgame.kt Perfect endgame solver
ui/
screens/ 40+ Compose screens
components/ Reusable Compose components
theme/ Material 3 color tokens and typography
viewmodel/ One ViewModel per screen, scoped to lifecycle
navigation/ Single NavGraph with deep link support
Requires Android SDK, JDK 17, and a Firebase project.
# Clone
git clone https://github.com/OutBlade/SudukoOnline.git
cd SudukoOnline
# Debug build
./gradlew assembleDebug
# Signed release build (uses env vars in CI, local keystore fallback)
KEYSTORE_FILE=path/to/release.jks \
KEYSTORE_PASSWORD=... \
KEY_ALIAS=... \
KEY_PASSWORD=... \
./gradlew assembleReleasePlace your google-services.json in app/ before building.
A GitHub Actions workflow builds and signs the release APK on every push to main and automatically deploys it to the download page.
Required repository secrets:
| Secret | Description |
|---|---|
KEYSTORE_BASE64 |
Release keystore encoded as base64 |
KEYSTORE_PASSWORD |
Keystore password |
KEY_ALIAS |
Key alias |
KEY_PASSWORD |
Key password |
DEPLOY_TOKEN |
GitHub PAT with repo scope for the download page repository |
- Create a project at console.firebase.google.com
- Add an Android app with package name
de.sudokuonline.app - Download
google-services.jsonand place it inapp/ - Enable Realtime Database in the Europe West region
- Deploy the included database rules:
firebase deploy --only database --config firebase/firebase.jsonThe firebase/firebase-database-rules.json file contains the required security rules and field indexes for all queries.
MIT