Kotlin Spinner Game

Simple spinner-like game intended to demonstrate capabilities of Kotlin/Native software stack

How to play

• Download and install the mobile application for Android or iOS
• The system will automatically assign you to a random team. Each team has a unique colour
• Spin the Kotlin logo using your fingers, or alternatively shake your phone
• Each two full rotations (i.e. 720 degrees) will increment your team's score
• The team with the highest score wins

Technical details

The entire application is implemented using Kotlin/Native

Server-Side

Server side runs on a linux server and is implemented using:

• microHTTPD HTTP server library
• SQLite for the database, storing score
• Jansson for JSON serialization and client/server communication

Client-Side

Android

Client side for Android is implemented in pure Kotlin/Native, as a Native Activity using:

• GLES version 3 interop for 3D rendering
• NDK input handling for input processing
• Open AL interop for sound playback
• Sensors native API
• libcurl file transfer library as HTTP client

iOS

Client side for iOS is implemented in pure Kotlin/Native using:

• GLES version 3 framework for 3D rendering
• UIKit framework for windows and views
• CoreMotion framework for sensors access
• OpenAL framework for audio playback

Implementation details

• Most graphical code, sound playback and user input reaction is shared between Android and iOS
• Server interaction on Android is asynchronous from the UI thread, using workers
• HTTP server works in multithreaded mode, state sharing between sessions performed via SQLite DB access
• Android app is split into separate loader and application code, so that dynamic library (libopenal.so) included with application can be used on older Androids
• WebAssembly frontend can fetch and render stats in the browser