# Touch Grass Bingo - offline nature bingo checked by an AI that lives on your phone > Source: > Published: 2026-10-09 15:48:53+00:00 *This is a submission for the [Hacktoberfest Open-Source AI Challenge Week 1: Touch Grass](https://dev.to/challenges/hacktoberfest-week1-2026-10-05)* ## What I Built **Touch Grass Bingo** is a nature bingo card that you play outside. You open it, get a seasonal card (a red leaf, an acorn, moss, a feather, a mushroom…), and put your phone away. When you find something, you take one photo. An open-weight vision model running on your phone checks it and marks the square. The center square is never free. It is **"Touch grass"**: a photo of your hand on real grass. Who it is for: - **Families** who want a reason to make a walk last longer. - **Run clubs and hiking groups.** Everyone types the same card code (like`FERN-42` ) and gets the same card. First to bingo wins. There are no accounts and no server. - **Anyone doomscrolling** who needs a nudge. If you photograph your monitor, the model detects a screen and tells you that you cannot touch grass through a monitor. The screen is the shortest part of the game: one glance at the card, then the phone goes in the pocket until you find something. ## Demo **Play it:** [https://prateekiiitg56.github.io/touch-grass-bingo/](https://prateekiiitg56.github.io/touch-grass-bingo/) Open it on your phone. Tap **Download photo checker** once on Wi-Fi (about 150 MB). After that, it works in airplane mode. **Play the same card as a friend:** [https://prateekiiitg56.github.io/touch-grass-bingo/?code=FERN-42](https://prateekiiitg56.github.io/touch-grass-bingo/?code=FERN-42) ## Code ### Offline nature bingo. Snap what you find outside; open-weight CLIP checks it on your phone. No signal, no uploads. # Touch Grass Bingo Offline nature bingo for walks, hikes and run clubs. The app deals you a seasonal bingo card (a red leaf, an acorn, moss, a feather…). You go outside and take a photo only when you find a square. An open-weight AI model running **on your phone** checks the photo. No signal is needed and no photo leaves the device. - **Open-weight model:**[CLIP ViT-B/32](https://huggingface.co/Xenova/clip-vit-base-patch32) (ONNX, 8-bit quantized) - **Open-source runtime:**[Transformers.js](https://github.com/huggingface/transformers.js) 3.7.6 on ONNX Runtime Web (WASM) - **No backend:** static files only. Host on GitHub Pages, Netlify or any static host. ## How it works 1. **Field kit.** On Wi-Fi, tap*Download field kit* . The model (about 150 MB) goes into the browser cache. A service worker caches the app shell and runtime. From then on the app works in airplane mode. 2. **Deal a card.** A card code (for example`FERN-42` ) seeds a deterministic shuffle of the season's item… ## How I Built It - **Model:**[CLIP ViT-B/32](https://huggingface.co/Xenova/clip-vit-base-patch32) , open weights, ONNX export, 8-bit quantized (about 150 MB). - **Runtime:**[Transformers.js](https://github.com/huggingface/transformers.js) on ONNX Runtime Web (WASM). Inference runs in the browser tab. - **App:** plain HTML, CSS and JavaScript modules. No framework, no build step, no backend. Hosted free on GitHub Pages. - **Design:** styled like a topographic map. Grid references (A1, B2…) run along the edge of the card, so a group can shout "got B2". A finished line is drawn as an orange trail-blaze route. - **Offline:** a service worker caches the app shell and runtime. Transformers.js caches the model weights in the browser. After a one-time download on Wi-Fi, the app works in airplane mode. The core trick is **zero-shot classification**. Each bingo square is only a text prompt, for example `"a photo of an acorn"`. When you take a photo, CLIP scores it against every item in the season's pool plus a set of distractors (a screen, an indoor room, a selfie, a document, a city street). On a laptop, one photo takes about 100 ms: - If the square you tapped wins, you found it. - If a different unfound square on your card wins clearly, the app marks that one as a bonus ("Not running water, but it is a mushroom"). - If a seasonal item that is not on your card wins, you get "Good find, but it is not on this card." - If a distractor wins, the find does not count, and you get a hint. My first version scored photos only against the squares on the card. In testing, a red maple leaf was marked as the "yellow leaf" square with 95% confidence, because it was the closest option. Scoring against the full season pool fixed this: the same photo now comes back as "red leaf, not on this card." Group play uses a seeded shuffle: the card code, season and size feed a hash, which seeds a small PRNG that shuffles the season's item pool. Every phone with the same code deals the same card, with no network. ## Why Does Open Innovation Matter? - **It works where the grass is.** Trails, parks and forests often have no signal. A closed vision API needs a network round trip for every photo. Open weights let the model live on the phone, so the game works in airplane mode. - **Photos stay private.** Families take photos of kids' hands, backyards and favorite spots. With an on-device model, no photo is uploaded to a server that the player does not control. - **It costs nothing to run.** No API key, no per-image bill, no rate limit. I can host it on GitHub Pages for free, and a whole run club can play without anyone paying. - **It is easy to change.** Because CLIP is zero-shot and open, a new square is one line of text. A teacher can make a "schoolyard" card, a birding club can make a "local birds" card, and anyone can swap in a different open model (for example SigLIP) by changing one constant. ## Prize Categories Best Use of Gemma Using Gemma, Google's open-weight model, in building my project