Project Fuchsia is an odd OS that Google quietly released on their Github. Recently, Fuchsia underwent a major overhaul, including a tectonic shift in kernels and a cleaned up UI dubbed Armadillo.
Developer Kyle Bradshaw downloaded the latest source code to Fuchsia, wrapped it up in a neat, little .apk file, and made it publicly available for free. All you need is an Android phone and the setting for installing outsider .apk files turned on (see here)
Learn more about Fuchsia here:
Download the Fuchsia APK here. (Direct Link)