Definitely not Swift Playgrounds and Google's “Coding for Carrots" doodle.
What it does
Play a simple score based game where you correct errors in various languages.
How we built it
UI was built completely using Android Layout Editor/XML/Kotlin. Backend logic is handled in Java using JSON for some storage.
Challenges we ran into
The a lot legwork for forming new questions.
Accomplishments that we're proud of
Completely native mobile application rather than web app.
What's next for CodeGame
Probably nothing but if there were a 2.0 including some more creative gamey/graphics based gameplay would be interesting.