This is a free open source application with no advertising and no special permissions. It is a flashcard-type quiz. You pick a word set, and then are given a key word, either in English or German. There and four choices, one of which is the correct translation. The orange bar at the bottom shows your progress through the set. If you miss a word, the app will ask you about it again until you get it right. The app orientation is always horizontal, gamepad-style.
The word pairs are based on Jörg Tiedemann's OpenSubtitles2012 project, as curated by Neil at http://germanvocab.com into a "top 3000" list. They're the top 3000 from TV shows, so there are a few oddballs like "stargate" that wouldn't be in a normal word list. The word pairs are pretty clean, but could certainly use more work. If you want to contribute to this open source project, see https://morris.cloud/open-german/ for more information.
Source code of app is by me, licensed GPLv3. Use OpenCSV (Apache v2). See https://github.com/xenotropic/open-german.
Berlin TV tower is CC-BY-NC, Flickr user justanotherhuman.
The word list was created by Neil at http://germanvocab.com and is based on Jörg Tiedemann using OpenSubtitles.org data http://opus.lingfil.uu.se/OpenSubtitles2012.php.