By day Product Owner at Assembly Global.
By night I make small, AI-powered tools and apps.
Solo, during nights and weekends.
In the past year, I've released a few iOS apps and one full-stack SaaS project. Luma Breathwork reached a 13.3% App Store conversion rate — much higher than I expected. And Lemmi Studio is now live and evolving.
A tool that turns raw app screenshots into ready-to-use App Store visuals, marketing copy and landing pages. Built to help indie developers who ship fast but don't have time for design or copywriting.
Tech: Node.js, React, Supabase, Gemini API, Stripe
Emotion tracking app for iOS that helps users reflect on emotional patterns with weekly AI-generated summaries. Built from idea to App Store in one week.
Tech: SwiftUI, SwiftData, CloudKit, Gemini API
A minimal, calming box breathing experience built in two weeks to explore focused UI design and StoreKit paywalls.
Tech: SwiftUI, SwiftData, CloudKit, StoreKit
A breathwork app that guides users through Wim Hof style sessions. Reached a 13.3% App Store conversion rate and holds a 4.9-star rating.
Tech: Swift, SwiftUI, StoreKit
Python · Swift · SQL · JavaScript
React · React Native · Next.js · Express.js · FastAPI · Flask · Firebase · Supabase
OpenAI · Gemini · Anthropic Claude · Perplexity · BigQuery
n8n.io · Make.com · Postman
VSCode · Xcode · Cursor · Git · GitHub · Docker
Figma · JIRA · Notion · Hotjar
© 2025 · Mateusz Byrtus · Warsaw, Poland