Wanderling

Creating a Buddy
Home
Battling
Walking

Inspiration

Everyone knows they should walk more, and almost nobody does it consistently. Step counters give you a number, and numbers get ignored after a week. We kept asking what actually gets people off the couch, and the answer was obvious: games and friends. People will walk miles to catch a Pokémon or keep a streak alive. We wanted to point that energy at everyday health, so walking stops being a chore and becomes the way you win.

What it does

StepBuddy turns your daily steps into a mythical beast you raise and battle with.

Walk to grow. Every 100 steps earns a Stride Point. Spend points to level up your beast, sharpen its attack and evasion, and evolve it from egg to baby, teen, and adult.
Collect beasts. 23 mythical species across four elements (fire, water, nature, sky), from common jackalopes to legendary hydras and thunderbirds.
Battle your friends. A turn-based fight where you choose to attack, guard, or charge a special move, and elements counter each other. Your stats come from how much you've walked, so the friend who walks more is genuinely harder to beat.
A buddy that's alive. Every beast gets its own AI-generated personality and voice. It cheers when you hit your goal, gets proud on a streak, sulks after two losses in a row, and remembers what it said to you.
Walk together. On the Map tab, a 3D version of your buddy walks beside you on a real map, following your GPS.
Rest and recover. A beast that loses a fight needs time to rest, which nudges you to walk while it recovers instead of spamming battles.
See your impact. Weekly step charts, streaks, your best day, total distance in km or miles, and the CO₂ you saved by walking instead of driving.

It runs in the browser and installs to your home screen like an app. No smartwatch or wearable is needed: your phone is the pedometer.

How we built it

Frontend: a mobile-first Progressive Web App in plain JavaScript, with no framework. It works offline through a service worker, and has retro pixel art plus sound effects for every punch, miss, win and loss.
Step counting: browsers have no pedometer API, so we built our own peak detector over the phone's accelerometer signal, filtering out gravity and jitter to pick out real steps.
Google Gemini: generates each buddy's personality (traits, a quirk, a speaking style, and which voice suits it) using structured JSON output. Then it writes in-character lines that react to your mood, streaks, level-ups and battles.
ElevenLabs: gives every buddy a real voice that matches its personality, and mood changes the delivery. Audio is cached so a repeated line never costs credits twice, and we pre-generate likely lines so the buddy answers instantly.
Google Maps + three.js: a 3D animated buddy walks on a live map, either a retro restyled map or a tilted 3D city with buildings. GPS distance counts toward your steps, and impossible jumps are filtered out to stop cheating.
Tiger Data (Postgres): stores players, steps, battles, friends and leaderboards. The server automatically falls back to a local SQLite database if Tiger can't be reached, so the game never goes down mid-demo.
Backend: Node.js 22 with almost no dependencies. The only package is the Postgres driver, and the test suite covers the game rules and the API end to end.

Challenges we ran into

There's no pedometer in the browser. We had to build step detection from raw accelerometer data and tune it until normal walking registered without counting every bump.
iPhone audio rules. iOS blocks sound that doesn't start from a tap, so voices and sound effects would silently fail. We "unlock" every audio channel on the first touch.
API rate limits. ElevenLabs caps how many requests can run at once, so we built a priority queue where live conversation jumps ahead of pre-generated lines.
Balancing battles. Our first design ended fights after five rounds, so upgraded beasts would "lose" while still sitting at 60 HP. We reworked the rules so fights go to a knockout and upgrades actually matter.
GPS noise. Phones report sudden jumps (tunnels, pockets, bad signal), which could have counted as huge walks. We filter out anything physically impossible.

Accomplishments that we're proud of

A buddy that genuinely feels alive, with a personality, a voice, moods and memory, which turns "go for a walk" into "go hang out with my dragon."
A complete game loop where health is the core mechanic, not a bolt-on: walking is the only way to get stronger.
Hardware-free step tracking that works on any phone.
An app that keeps working even when outside services fail: built-in lines without Gemini, the browser's voice without ElevenLabs, local storage without Tiger.

What we learned

Motivation beats measurement. People don't need more data about their steps; they need a reason to care about them.
How to run game logic on the server so battles and points can't be faked from the browser.
A lot about prompting for consistent characters: keeping a personality in-voice across hundreds of lines is harder than generating one good line.
That the most interesting part of our team was always hidden a few layers down.

What's next for StepBuddy

Real-time battles and friend challenges, such as "most steps this weekend wins."
Native apps so steps count in the background all day, using Apple Health and Google Fit.
Group events where a whole class or office walks together to defeat a giant boss beast.
Accessibility modes that count wheelchair pushes and other movement, so everyone can raise a beast.