About
Yohann Dandeville
Full-stack developer & founder of YdvSystems
I build business software, SaaS platforms, AI integrations, voice assistants and animated video ads. My approach: clean code, solid architecture, and an obsession with the finished product.
Background
Trajectory
It all started long before any formal training or certifications. In the late 2000s, I built a website for a clothing brand project, a professional Myspace with custom code integration — at a time when only major music groups were doing that. Then a site of over a hundred pages for an association dedicated to sharing knowledge: press articles, videos, collaborative files. Self-taught, curious, convinced that the web could serve projects that needed it.
In 2011, I took over the presidency of a failing sports club — martial arts, dance, weightlifting, 400m² that no longer worked. I didn't arrive as a manager. I arrived with a vision.
From the start, I structured it legally: an association for the activity, a limited company in parallel to handle purchases, communications, infrastructure. Two entities, two logics, one direction. Two and a half years running this dual architecture, then I simplified — the company disappeared, the association remained, but deeply transformed.
It was no longer a sports club. It was a cultural centre. Concerts, café-theatre, exhibitions, workshops. In the sixth year, I created the performance hall and expanded the space to 700m². What I had found failing became a living place, rooted in its neighbourhood — and still exists today.
Throughout all those years, in parallel and in silence, I kept coding. The Union des Arts website, digital communications, online tools. In 2021, a two-year web developer qualification. Not a new start — the validation of a journey that had begun long before. What leadership taught me added to the rest: understanding an organisation's challenges before opening an editor, knowing what a tool must solve to be actually used, not just delivered.
Work
What I've built
Since then, I've built very different projects — and that's intentional.
Animated video ads
A turnkey motion design offering: brief, script, animation, sound design, delivery in 5 days. The first film — the 48-second Plume teaser — is written in React on a deterministic timeline engine: the diagrams are computed SVG, the sound effects synthesised with the Web Audio API and tuned to the music, the render exported frame by frame then muxed to H.264. No editing suite: code.
Présence Pro
Turnkey showcase websites for craftspeople, shops and freelancers — designed, deployed and maintained end to end. Six trade demos online, each with its own design, content and photography: plumber, electrician, hairdresser, hypnotherapist, plasterer, coach. Astro + React, a Lighthouse score close to 100, European hosting, zero tracking cookies. Online booking, spam-proof forms, analytics: the client has nothing to install and nothing to manage.
YDV Platform
4 SaaS platforms for the social inclusion and training sector. Multi-tenant architecture, RBAC, multi-provider AI, +8,000 automated tests. 102 phases carried out alone, from the database schema to hosting on dedicated infrastructure. What others do as a team, I do alone — not to save money, but as an architectural choice.
Plume
My most architecturally ambitious project. Built on one conviction: writer's block is a structural problem, not a shortage of ideas. 17 thematic universes, 12 of which can be combined per project, 30 classified narrative structures, a five-axis voice engine, and an AI co-pilot with 10 levels of progressive assistance. The manuscript stays on the machine — a SQLite file, never in the cloud — and the AI runs BYOK: the author pays their provider directly, with no subscription. V1.0 in its final stages, around 1,370 tests. Nobody else does this in the French-speaking market.
Sophia
A French voice assistant, built in the open: the real code and the logbook of its construction, decision after decision, commit after commit. A local end-to-end voice pipeline — capture, speech detection, transcription, speaker recognition, synthesis. And a memory that holds: by the 88th conversation she still remembers the first, and she says where she gets what she asserts. Every piece of work goes through two adversarial reviews before it is locked. This project demonstrates a method as much as a product.
Enterprise AI Audit
A diagnostic tool answering a single question: where, how and under what conditions AI can create concrete value in a company. An adaptive questionnaire calibrated for 14 sectors, a diagnosis along 4 axes — organisation, systems, data, culture — a maturity score out of 100, and the identification of priority use cases by crossing business problems, available data, feasibility and value. A report, not a promise.
Le Prompt Parfait
A PWA available on web, desktop and mobile from a single codebase. A free tool to optimise AI prompts, designed to be accessible to everyone. A simple idea, careful execution, a result that is immediately usable.
Les Mots de Marilyn
A blog designed for a person living with Parkinson's. Three writing modes depending on how the day is going — type, dictate, or be guided by a prompt on days of cognitive fatigue. Voice transcription with a provider fallback chain, audio playback of articles, WCAG AAA compliance, click targets of at least 60px. The project where accessibility was not a checkbox but the starting constraint.
Pills Stadium
A 3D kart racer in the browser with AI opponents and real-time physics — pure WebGL, no third-party engine. The central technical constraint: a figure-of-eight circuit with elevation to form a genuinely coherent 3D loop. Playable with keyboard, gamepad and on mobile, straight in a browser, with no installation.
Le Château de Dracula
Over 40 distinct visual environments — freezing crypts, gates of hell, celestial cathedrals, cursed chapels — each with its own lighting, palette and ambient animations. Creeping fog, flames, lightning, smoke. Playable with keyboard, gamepad and on mobile. Sound design with the Web Audio API. The project that best illustrates my creative side — technique in the service of emotion.
Approach
Approach
I think deeply before writing the first line of code. Understanding the real need, identifying what truly matters behind the specs, anticipating what will cause problems later — that's where a project's quality is determined, not in the speed of execution.
Clean code, scalable architecture, zero over-engineering. I work solo — responsive, focused on what matters, no unnecessary meetings. Creative when the project calls for it, methodical when production demands it. You're talking directly to the person who codes.
Values
What guides my work
Uncompromising quality
8,000+ automated tests across my platforms. Clean code isn't a luxury — it's the only way to deliver reliable products.
Full transparency
Published pricing, auditable source code, no surprises. You know exactly what you're paying for and what you're getting.
Real-world impact
Every line of code must solve a real problem. No gimmick features, no over-engineering.
Responsiveness
I work solo, which allows me to be responsive and focused on what matters. No unnecessary meetings, no management layer between you and me.
What motivates me: solving a real problem for a real need — not delivering code for the sake of delivering code.
Front-end
Back-end
Databases
Artificial intelligence
DevOps & hosting
Cross-platform
Tools & integrations
Have a project in mind?
Describe your needs and I'll get back to you within 24 hours with a concrete proposal.