Gromit Unleashed 3
- Russ Morris
- Jul 10
- 6 min read
Over the last few months, I've been busy working away on building the companion app for the Gromit Unleashed 3 sculpture trail, taking place in Bristol between June 30th and August 31st, 2025. The trail’s purpose is to raise money for The Grand Appeal, a dedicated charity supporting Bristol Children's Hospital and the Neonatal Intensive Care Unit at St Michael's Hospital.
Trails have become an important part of the summer for a lot of people in Bristol and the South West. There have been the previous Gromit Unleashed trails (2013, 2018), Shaun in the City (2015), and more recently the unicorn trail, which took place in 2024.
It’s been a real privilege to collaborate with The Grand Appeal on this project — the entire team there is so passionate about what the trail means, not only to The Grand Appeal as a charity but also to the general public. In addition to the team at The Grand Appeal, the app development team consisted of myself as developer and George Rowe and Laura Beavan, who produced the trail and made sure that by the time things got to me, they were ready for development. For me, as the developer on a project, that's the sign of a good producer (or producers in this case). Good producers aren't just there to answer emails and arrange calls - they also know the project inside out. Good producers ask the questions you want answered even before you realise you need them answered yourself. For such a small team, the success of this project was really down to the hard work that George and Laura put, in making sure everything stayed on track. A particular mention must also be made for Isabel Lawton from The Grand Appeal who was responsible for much of the design and UX of the app. They did a really great job putting together an app that was intuitive, clean and contained personality.
In terms of features, the app is designed to act as a companion for the trail: informing users of sculpture locations, providing curated mini-trails, and serving as an interactive checklist so users can keep track of exactly which sculptures they've found. We also included a series of awards designed to keep users engaged and reward them for completing challenges or reaching certain milestones.
On the technical side, the app was built using Flutter — a perfect choice for an app like this. Heavily UI-driven but with scope for snappy transitions, rewarding animations, and reliable cross-platform deployment on iOS and Android.
One of the biggest technical challenges to solve was the mapping functionality. It's not necessarily difficult to integrate maps (there are plenty of options out there), but the difficulty comes from finding the solution that is right for the project. For this project, the main questions to answer were:
We need a mapping solution that is lightweight, performant and allows us to place around 100 custom markers on the map, along with showing the user's current position.
It needs to be flexible enough so that we can use different tile data or rendering types - including the possibility to provide local, offline map tiles.
We need a mapping solution that is...for want of a better word, CHEAP.
Solving the first question was fairly straightforward — there are multiple options out there. In the end, we chose to use the maplibre_gl package, which allowed us to fulfill our requirements from a usability perspective (custom map pins, etc.). It was also flexible enough to explore different ways of technically implementing the map data, thanks to its support for various data types and tile sourcing. That answered question 2 for us as well. So far, 2 out of 3.
Solving the third question of doing it cheaply... well, that's not so easy. Anyone who's spent more than five minutes looking at map tiles and data knows that it gets expensive, FAST. I like to compare map tiling costs to the "ripe banana" theory. For a moment it seems fine, then you turn your back for a second and — BOOM — your banana is rotten. Maps are similar: at first they seem cheap, then you go one user over the free quota and suddenly it’s a billion pounds (roughly) for the next five trillion map tiles. So how do you solve that? Well, you just happen to find someone doing the type of work that's going to earn them a sainthood: hosting map tiles of the world for free. That person is Zsolt Ero, the creator of OpenFreeMap.org.
By simply plugging in the tilemap endpoint to maplibre I was able to have free map data and answered the third question- well, not just answered it, but it saved a lot of time and money. How much money? How does 100% sound? Or, if you're a fan of numbers and have ever used a map tile cost estimator then anywhere from £1 to £1,000,000,000 - so yeah, pretty good saving! Thank you Zsolt Ero. If you need map tile data for your app then check out OpenFreeMap.org and be sure to make a donation to the running costs as it's an invaluable resource for apps such as Gromit Unleashed 3.
Behind the scenes, Directus handled all the app's content management. I've used Directus on a few projects now, and each time I’m reminded just how much heavy lifting it does. It allowed us to manage sculptures, trails, achievements, FAQs, app copy, and sponsor information, all in one place. Updates could be pushed out seamlessly without requiring app updates, which made it easier to keep everything fresh throughout the trail. Directus also has a lovely little feature called "Insights," which lets you visualise your data directly in the CMS. It's not the most powerful or feature-rich solution for data visualisation, but being able to quickly see our app data in the same place it’s managed has been really useful. For Gromit Unleashed 3, we capture certain app events so that we can track things like the number of sculptures unlocked and when our busiest times of day are.
Beyond the core functionality, the app also includes a custom achievements system that rewards users for discovering sculptures and completing mini-trails. We built a dynamic award popup system with custom animations to celebrate each new milestone. The app even tracks detailed user progression locally, syncing key updates to Directus so data stays up-to-date while still working reliably offline. We then coupled this with a user account restoration feature, which assigns each user a unique ID on sign-up. If a user loses their device or needs to reinstall the app, they simply re-enter their recovery ID to restore their progression. This solves one of the main issues from previous trail apps where users would lose progress.
Other features like offline-friendly progression, advanced filtering and sculpture searching and a smooth onboarding flow meant paying close attention to both technical detail and user experience. These are all really important features and are expected by most users as standard. Not only should they be there, but they have to work - and not only should they be there and work but they should also offer something to the user by way of visual feedback that matches the style of the app and the personality of the brand. We spent a lot of time making sure that the way the user interacts with the app and the way that it animates always gives something back and matches the personality of the underlying brand.
It’s these little touches — things like carefully animated award popups, parallax effects, and thoughtfully designed navigation — that help make the app feel inviting and rewarding. That's one of the things I really like about Flutter, particularly after working for so many years in Unity; you can get to the little things (that mean so much) quickly. Flutter does so much of the heavy lifting to get your app on screen that you can focus more on how it looks and feels than on just getting it rendering.
As always, it's the blend of tools, people, and purpose that makes a project memorable. I feel lucky to have had the chance to help bring Gromit Unleashed 3 to life digitally and support a cause that means so much to Bristol. Gromit Unleashed 3 is available now for iOS and Android for the duration of the sculpture trail.
Even if you're not in Bristol, you can read more about The Grand Appeal and donate online here.