KRFT
Design and engineering · 2026
A craft beer bar discovery app for Tokyo.
Flutter, Next.js, Firebase
Spring Theories
A small Tokyo studio building mobile apps and web products.
I'm Julian. I design and build mobile and web products with Flutter, Next.js, Vue.js, and Firebase — handling everything from UI/UX design to product strategy.
From client work to my own products, I move across disciplines and domains.
Services
Web platforms
Next.js, React, Vue.js, Nuxt.js, Firebase, GCP — or WordPress when that's the right answer.
I take projects from frontend through backend, deployment, and infrastructure.
Mobile apps
Flutter for iOS and Android from one codebase.
I take it through store submission, signing, and the release pipeline.
Product design and strategy
Discovery, prototyping, roadmaps.
Roadmaps and prototypes from someone who'll be the one shipping them — so scope stays grounded in what's actually buildable.
Selected work
Orange Lady
Design and engineering · 2025
Independent music label and its evolving online home.
Next.js, Firebase, WordPress
Sonbei
Design and engineering · 2020
A Tokyo music event platform for artists, live houses, and music fans.
Flutter, Next.js, Firebase
About
Spring Theories is the studio name I work under in Tokyo. Most of what I do is design and build mobile and web products — sometimes for clients, sometimes for myself.
I'd rather ship a small thing that's finished than a big thing that's stalled. That bias shapes how I scope and what I push back on — fewer features, sharper decisions, and a real product in people's hands while the ambitious version is still a deck.
Contact
If you'd like to talk through a project, send an email or book a call.
- hello@springtheories.io
- Book a call
- cal.com/springtheories
- linkedin.com/in/julianspringaux