900k+ downloads

Cross-Device Sync

Challenge: Users needed to sync bookmarks, notes, and workspaces across multiple devices.

Solution: Delta-based cloud sync with pluggable storage backends (Google Drive, NextCloud). Only changed data is transferred, minimizing bandwidth and sync time.

Result: Thousands of daily users syncing seamlessly across devices.

★★★★★ "The best Bible app that I've used thus far... I also love the features and the design of the application, how everything is easily accessible to me and the smooth synchronisation." — Google Play Review

900k+ downloads

Bookmarks & Highlights

Challenge: Users needed a rich annotation system: highlights in different colors, notes, and organization by topic. Traditional apps only support whole-verse highlighting.

Solution: Character-level precision for text selection, overlapping highlights with CSS/SVG layers, label system for categorization, and StudyPad for collecting notes into documents.

Result: Flexible annotation system that scales to thousands of bookmarks with search, export, and cross-device sync.

★★★★★ "Really appreciate the app... the ability to have personalized bookmarks and make personal notes. I also like the ability to backup the bookmarks and notes." — Google Play Review

900k+ downloads

EPUB Support

Challenge: Users wanted to read EPUB books alongside Bible texts, but the existing architecture only supported specific formats.

Solution: Adapter pattern integration into the existing architecture. EPUB files appear as native objects—no changes needed to upper layers. Performance optimized via fragmentation, compression, and SQLite indexing.

Result: Seamless format support with full-text search. Same architecture now powers MySword and MyBible formats too.

★★★★★ "Being able to add my own epubs and the scripture references auto hyperlink is wonderful!" — Google Play Review

900k+ downloads

Workspaces

Challenge: Users needed to manage multiple study environments—for daily reading, deep analysis, and different contexts.

Solution: Workspaces feature: unlimited environments with their own windows, settings, and reading positions. Quick context switching with swipe gestures, drag-and-drop arrangement.

Result: Modern workspace concept for mobile Bible study. Users can customize environments for different needs.

★★★★★ "Love the app, all the features are amazing. I love that you can hide highlights in different workspaces, so hard to find that feature!" — Google Play Review

900k+ downloads

Vue.js Rendering Engine

Challenge: Complex XML data (OSIS, TEI formats) needed flexible rendering in a mobile app. Traditional solutions required heavy parsing or static template mappings.

Solution: Vue.js rendering system that transforms XML directly into Vue components dynamically. Modular architecture: each OSIS/TEI element is an independent component.

Result: Maintainable architecture that handles complex XML formats. Adding new features is straightforward—XML structure defines the UI.

★★★★★ "Hands down, my favourite! Easy, quick, no loading... great customization, a single tap to open or close other documents." — Google Play Review

New project

MIDI Recorder — Real-time BLE & USB MIDI capture

Challenge: Help improvising musicians keep every spontaneous idea on tape. Record Bluetooth and USB MIDI keyboards directly to Standard MIDI Files on both Android and iOS, with accurate timing and no studio overhead.

Solution: A Kotlin Multiplatform core shared by both apps, with BLE timestamp-based tick computation (not wall-clock), silence-based auto-stop, first-note smart start, pedal-triggered start/stop, metronome, a live staff view with real-time chord analysis, and a home-screen mini view of the app on the launcher.

Result: A focused utility that plays nicely with any DAW — no accounts, no cloud lock-in, and every feature is free. Shipping on Google Play and the App Store. Read more →

★★★★★ "Fantastic! Perfect notepad, automatic export to .mid, metronome. No crashes, easy to use, also accepts MIDI over Bluetooth. A real treat!" — Google Play Review

Open source · GPLv3

JailBee — One container per branch

Challenge: Working on several branches at once collapses into port conflicts, shared database state and twenty-minute branch switches. At the same time, AI coding agents need a real sandbox rather than trust: their reach into the machine and the network has to be bounded, or you cannot leave one working on its own.

Solution: Every branch gets its own Incus system container, cloned copy-on-write from a single golden image — its own services, its own Docker daemon, its own IDE and browser through Wayland passthrough. A git bridge moves commits straight between host and container, submodules included, a kernel-level egress allowlist bounds what the container can reach, and one dashboard covers every project.

Result: Several full stacks running in parallel on a single host, a new container up in about a minute, and coding agents left to work unattended behind a strict allowlist. Designed and built by me at GISGRO Oy, released as open source under GPLv3 and installable from PyPI. jailbee.gisgro.io →