Flutter
Google's cross-platform framework — one codebase (Dart) builds iOS, Android, web, desktop. Own render stack (Skia, then Impeller).
Stable in 2018. Widget tree architecture (everything is a widget). Hot reload is the killer feature for developer ergonomics. Competitors: React Native (JS, Meta), .NET MAUI (C#, Microsoft), Tauri/Wails (web-based desktop). Used by: BMW, Alibaba, eBay Motors, Toyota infotainment, Google Earth web (Flutter Web). Google team reduced in 2024 → concern about long-term support.