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Portrait of Stefan Oltmann - Kotlin Developer
Kotlin Developer

Stefan Oltmann

Building apps with Kotlin 🚀

Discover my apps

Mines+

Mines+ is a solvable Minesweeper puzzle game.

Enjoy a beautiful, intuitive UI with customizable board and difficulty. The game works fully offline.

An algorithm ensures that the puzzle can be solved and you don't have to guess.

Mines - Modern Minesweeper game for Android and Windows

Thumbnail Fixer Pro

Enhance and repair embedded image thumbnails to improve both quality and usability.

Sharper, high-quality thumbnails speed up previews in Windows Explorer, Apple Finder, and many photo apps.

Works entirely offline, with all processing done locally on your device for complete privacy.

Thumbnail Fixer - Optimize and repair embedded image thumbnails

EXIF Viewer

Inspect image metadata in detail, all the way down to a hex-level view of the structure.

Supports a wide range of photo formats.

Runs entirely on your device. Your photos never leave the browser.

EXIF Viewer - Detailed image metadata and hex structure analysis

PixelSafe

PixelSafe is a tool for securely hiding data within PNG images.

Steganography allows you to conceal information in plain sight, making it invisible to the casual observer.

With PixelSafe, you can embed any file into a screenshot, with optional encryption.

Works fully offline, with all data processed locally on your device.

PixelSafe - Hide data securely in PNG images using steganography

MapsNotIncluded Map Explorer

For the MapsNotIncluded project, I developed a seed browser for the game Oxygen Not Included.

The tool allows a large database of maps to be quickly searched using complex criteria, making it easy to discover interesting seeds.

Each map’s properties are presented in a clear and visually appealing way, enabling quick overviews and easy comparisons.

MapsNotIncluded Map Explorer Screenshot - Seed Browser for Oxygen Not Included