Looking Back at Shift 2025 - The Gen AI Hackathon

Welcome to Shift, a hackathon dedicated to generative artificial intelligence which was held in Nantes from March 28 to 30, 2025, and to which I contributed as a participant.

What follows is not a factual report of the hackathon. Instead, it's my personal retrospective: They are key moments, the challenges encountered, and the ideas from our project that emerged over this intense weekend. Follow along!

Opening Ceremony

The hackathon kicked off on Friday evening with the arrival of participants and the distribution of badges, marking the start of the weekend. At 7 p.m., the opening speech laid the foundations for the event while outlining the hackathon objectives and themes to explore:

• Health: Develop projects aiming to make healthcare more accessible through generative AI.
• Culture: Create applications to enrich cultural experiences.
• Education: Design tools to improve and accelerate learning.

Next, a pitch session allowed everyone to propose a project idea - 26 in total, creating a buzz of ideas and excitement that I couldn't ignore - this information is significant for what follows.

Then the evening concluded with the announcement of the 12 ideas chosen by the participants through a voting system, and the formation of teams around these ideas. This was followed by a first work session to define the project direction, laying the groundwork for what was to come.

Improvised Pitch

My objective for this hackathon was to join a team, contribute my experience, eat pizzas, broaden my knowledge in Gen AI, and forge connections with other participants, coaches, and organizers. In other words, my priority was expanding the Premier Octet network, not necessarily bringing home the victory.

However, while listening to the opening speech and the initial participants’ suggestions, an idea began to form. Then, almost without thinking, at the last moment, I raised my hand and took the mic to pitch Uchronia in 3 minutes.

“Do you know what a uchronia is? It's a fictional reconstruction of history, recounting events as they could have occurred."

In the room, a few heads nodded in understanding. So, I continued:

"What if Christopher Columbus hadn't discovered America? What if Kobe Bryant had been drafted by the Boston Celtics? What if the Egyptians had invented gunpowder?"

I had captured their attention, and I explained the idea: A narrative game powered by artificial intelligence that allows the player to rewrite history in each game session. The player picks a starting scenario, makes strategic decisions, and the AI adapts in real-time to generate the next steps in the story.

To be completely honest, I didn't have high hopes for it and didn't vote for my project during the selection. Against all odds, it was chosen as the fourth most popular, so I had to form a team of 5 or 6 people and bring to life this impromptu idea I had jotted down on a piece of paper half an hour earlier.

A number of participants asked me how the game worked, and my answer frequently amounted to these four words: "I don’t know." At this stage of the weekend, I was questioning whether I had gotten in way over my head or if this would turn out to be a cool experience. Spoiler alert, stick around until the end, because it was genuinely super cool. Yes, this is Hollywood.

Cool Team, Cool Weekend

My first hackathon revealed a fundamental truth: The experience fundamentally depends on the team's synergy. Uchronia is proof of this. The project’s flexibility also turned out to be a major advantage; since nothing was set in stone, each team member was able to contribute their vision of the game. This strengthened the involvement and the sense of belonging. Uchronia quickly became a collective adventure.

Introducing our weekend team:

• Michaël and Denis: Product Managers (PMs), responsible for the overall vision and user experience.
• Julien: Artistic Director, who contributed a strong visual identity to the project.
• Léo: Cloud Engineer, responsible for the infrastructure.
• Vincent: Front-end Developer, responsible for the game's smooth and intuitive interface.
• Slava and Mehdi: AI Experts, who designed and trained an AI engine capable of generating believable and interactive scenarios.

At 10 p.m., our team dove into a brainstorming session on how to structure a game that accommodates an infinite number of possible scenarios.

We decided to go for a simple and effective system:

• Short gameplay sessions, between 10 and 20 minutes.
• At each step of the game, users can choose between two impact-driven options.
• An AI engine generates the narrative and visuals in real time.

As the evening drew to a close, the broad outlines of the game began to take shape, and the foundations of Uchronia were laid. We agreed to meet again at 9 a.m. the next day to start the work.

The Weekend - Saturday / Sunday

We kicked off the day by dividing tasks. Michael and Denis, our Product Managers, and Julien, our Artistic Director, brainstormed subjects related to game design and the user interface (UI).

Mehdi, Slava, Léo, and myself commenced the first iterations of the project on the technical side. We contemplated AI functionality, experimented with the LLM provided by Shift (Mistral, Seelab), and set up the server, the API, and the front-end.

It's worth noting that throughout the weekend, we had coaching sessions with Gen AI and product management experts. Among the coaches were professionals like Michel-Marie Maudet, founder of Lucie AI, Adrien Etaix, UX/UI specialist at Mistral AI, Benoit Hediard, founder of Globetrotters.ai and former co-founder of Agorapulse, as well as Ronan Tessier, CTO at Seelab. A huge thanks to them for their advice and support throughout the weekend!

By Saturday afternoon, the still-rough AI demonstrated its potential, and the first prototype took shape - we were ready to welcome our first tester.

This user test helped us refine the system. We tested, adjusted, debugged - it was a race against the clock. Our goal: to create a smooth user experience, free from any blockages related to content generation.

Gen AI at The Service of Uchronia

For Uchronia, generative artificial intelligence sat at the heart of our creative endeavor. To bring our uchronian universe to life, we explored the possibilities offered by Seelab, an image generation tool allowing us to visualize alternative scenarios and characters. Seelab helped us to rapidly concretize visual concepts, thereby enhancing the gameplay experience.

The AI from Mistral helped us to explore the creation of textual content, generating descriptions of events and historical scenarios influenced by previous user choices.

The game design of Uchronia rests on a simple mechanism: the user chooses a key historical event and is presented with two options, each represented by a distinct visual and action. Their choice triggers an AI-generated consequence, altering the course of history.

Herein lies the technical challenge: to ensure the timeline's coherence, the consequences are analyzed by the LLM Mistral, which generates new correlated textual events. These events are then used by Seelab to create visuals. However, the generation time, which can reach up to 12 seconds, necessitated an alternative.

We introduced a RAG-system that pre-generated 1000 images covering a broad spectrum of historical events. This way, a relevant placeholder image appears immediately on the Timeline, allowing the user to continue their progress without waiting for the final image to be generated. When the Seelab-prepared image is ready, it replaces the placeholder.

This hybrid approach, combining real-time generation with pre-calculated storage, ensures a fluid user experience while exploiting the power of AI to rewrite history.

We also utilized Suno: an audio generator that provided a sonic dimension to each of the alternative realities explored by the players. Each new historical event created was associated with one of 30 generated audio tracks.

Thanks to the Shift 2025 Team

A massive kudos to the Shift 2025 organizing team. Thanks to them, this event was so much more than just a hackathon. It was a powerful experience where the collective energy and desire to create was palpable. Their capacity for structuring such an intense weekend while allowing room for spontaneity made it possible for projects like ours to come to life.

A big thanks to the coaches who gave both their time and expertise. Whether for technical advice, an external perspective on a prototype, or just a word of encouragement in the middle of the night, their presence was invaluable.

Homestretch

On Sunday evening, it was finally time for the final pitch. The game worked. The AI responded to the user's decisions, generating consistent outcomes. The story adapted and unfolded smoothly.

Each of the 12 projects had 5 minutes for presentations and 4 minutes of Q&A with the jury composed of Constance Nebbula, Vice President of the Pays de la Loire Region, Jean-Pierre Besnard, Head of Innovation at Ouest France, Bastien Massé, Director General of Class'Code, and Tugdual Grall, Solutions Engineer at GitHub.

We were the 9th group to present, and Michael took the stage to present our deck. The jury liked it. We finished in third place. We were thrilled!

As I write this, Uchronia is available online and we haven’t yet exhausted all our IA generation credits. So it's possible to test the game on a desktop.

For those interested, Uchronia will probably continue to evolve gradually, especially in terms of graphics and responsive design. We'll keep you updated, through LinkedIn for example.

Congratulations to all the teams, and see you next year!