Christoffer worked on the android/nowinandroid repository, focusing on optimizing the release build process to enhance user experience by reducing APK size and descriptor overhead. He introduced the -repackageclasses flag in the R8 configuration and added a proguard-rules.pro file, enabling class re-packaging during release builds. This approach streamlined the build output, resulting in smaller APKs and faster downloads. Using Kotlin and Gradle, Christoffer applied his skills in Android development, build configuration, and optimization to address the challenge of application bloat. The work demonstrated a targeted, technical solution to improve build efficiency within a short, one-month development period.