Made independently by Martin Grüner
Software for focused work—and play.
Practical productivity tools, mobile apps, and original games—built from the first sketch to the final screen.
Productivity
Tools that stay out of the way.
Local-first desktop software for building, comparing, and publishing digital products.
DevDock
A local development workspace for projects, commands, databases, and security checks.
Screen Studio Kit
Design every store screenshot from one reusable composition.
Diff Anything
Compare the files developers actually work with—not just text.
Apps & games
Different screens. Same curiosity.
Two games and a mobile testing app, each designed around the device it lives on.
Free browser tools
Check the release before the release checks you.
Focused, local utilities for store assets and API compatibility.
Store Screenshot Validator
Check screenshot dimensions, format, transparency, count, and store-specific constraints before upload.
Validate screenshots →API compatibilityOpenAPI Breaking Change Checker
Compare two OpenAPI or Swagger descriptions and review likely client-breaking changes.
Compare API specs →