Back Up

Multiplayer Card-Driven Board Game for iOS

February 2026 – Present

Personal projectPrivate repo

Back Up is a board game for 2 to 6 players that I designed and built end to end: a React Native iOS app and a Node.js game server. Cards decide how your pieces move, partners play as a team, and you can play on one phone, against bots, or online in real time or one turn a day.

The same rules engine runs on the phone and on the server, so local games, bots and online matches all play by one set of rules.

Screens

Bots fill the other seats in these matches.

Swipe to browse.Scroll sideways or use the arrows. Tap a screen to enlarge it.

Back Up game board in round 6 of a 4-player match. A cross-shaped track of marble slots with colored home bases in each corner and colored safe-zone lanes leading to the center, seat labels for You, Yellow Bot, Orange Bot and Green Bot, and the player’s hand of four cards below: King, 7, Jack and 5. — Gameplay
A 4-player match: you and Yellow Bot against Orange and Green

Main menu

Play on one phone or online

New match setup screen with player counts from 2 to 6 and 4 selected, a rules panel for number of pieces, animation speed, free play and partner play, and seats split into two teams with You and Yellow Bot on Team 1 and Orange Bot and Green Bot on Team 2. — Match setup
2 to 6 players, teams and bot difficulty

Tutorial step 4 of 10, The Back Up Rule. A message explains that the player’s own pieces block every move and asks them to tap Drop Hand, above a section of the board and two cards, a 2 and a 6. — Interactive tutorial
Ten steps played on real game states

Game over screen announcing You and Blue as the winners after 18 rounds, with highlights: Executioner with 5 knockouts, Punching Bag knocked out 5 times, Backed Up Most 4 times, and Globetrotter with 410 spaces travelled. — Results
Match highlights after every game

How it plays

Each turn you play one card to move one piece around the board and into your safe zone. Recorded in the app:

A King is played and a red piece moves out of its home base onto the track. — Leave home
An Ace or a King brings a piece out onto your start space.

A 5 is played and a red piece lands on an opponent’s piece, which is sent back to its home base. — Knockout
Land on an opponent and their piece goes back home.

A Jack is played and a red piece swaps places with an opponent’s piece on the track. — Jack swap
A Jack trades places with any other player’s piece on the track.

A Backed Up banner appears with the note Dropped 2 cards, after the player has no legal move. — Backed up
You can’t pass your own pieces. With no legal move, you drop your whole hand.

The final piece reaches its safe zone and a banner announces You and Blue win. — Team win
Partners sit across the board. First team home wins.

What it does

2 to 6 players, with teams

Partners sit across from each other in 4- and 6-player games. With 3 or 5 players, the game starts free-for-all and switches to teams once the first player finishes.

Pass-and-play with bots

Play on one phone with a handoff screen between players, and fill any seat with an Easy, Medium or Hard bot.

Live online matches

Lobbies with join codes, a 45-second turn timer and pause by vote. If someone drops and doesn’t reconnect within 30 seconds, a bot takes their seat.

Async games

24-hour turns with push notifications, and a catch-up replay of the moves made while you were away.

Interactive tutorial

Ten steps played on real game states, from leaving home to the Back Up rule and jack swaps.

Spectating and replays

Ask to watch a friend’s game, and step through any finished game move by move.

Ratings and friends

ELO ratings, a leaderboard, ranked stats and a head-to-head record against each friend.

Match highlights

Every game ends with highlights like Executioner for the most knockouts and Globetrotter for the most spaces traveled.

How it’s built

App

React Native 0.81 and Expo SDK 54 with Expo Router
Board drawn in SVG, with Reanimated piece movement and pinch-to-zoom
Engine events feed an animation queue that drives piece moves, sounds and haptics
Light, dark and system themes, plus board skins

Game engine

Plain TypeScript with no UI code: each move takes a game state and returns a new one plus a list of events
Generates every legal move per card, falling back to a partner’s pieces and then to dropping the hand
The server compiles the same engine, so the phone and the server play by one set of rules

Bots

Easy plays a random legal move; Medium scores moves with hand-tuned rules
Hard plans out the rest of its hand within a 30 ms budget, weighing knockout risk from the cards it hasn’t seen
Bots see only their own hand, the same view a human player gets
A bot-vs-bot tournament harness measures each new Hard bot against the last

Game server

Express 5 and Socket.IO 4 with the Redis adapter
Checks every move against the engine’s legal moves before applying it, and sends each player only their own hand
Redis holds live game state, per-game locks, turn deadlines and rate limits
PostgreSQL through plain SQL with 24 versioned migrations
JWT access and refresh tokens, ELO ratings and Expo push notifications

Reliability

Move numbers and idempotency keys, so a retried move is applied once
Reconnects with backoff and a fresh token, then sends any moves queued while offline
A per-game Redis lock that only its owner can release

Testing and delivery

700+ Jest tests across the engine, bots, server and UI, plus Maestro end-to-end flows
CI type-checks, lints and tests the app and the server on every pull request
The server deploys from a self-hosted GitHub Actions runner with PM2 and a health check
iOS builds ship to TestFlight

React NativeExpoTypeScriptReanimatedNode.jsExpressSocket.IOPostgreSQLRedisJestMaestroGitHub ActionsSentry

Let's Work Together

I'm always interested in hearing about new projects and opportunities. Whether you have a question or just want to say hi, feel free to reach out!

Get In Touch