The Android platform provides a framework API that applications can use to interact with the underlying Android system. The framework API consists of: A core set of packages and classes. A set of permissions that applications can request, as well as permission enforcements included in the system

Firebase is a platform developed by Google for creating mobile and web applications

Google Play services offers a standard authorization flow for all Google APIs and all components of Google Play services. In addition, you can leverage the authorization portion of the Google Play services SDK to gain authorization to services that are not yet supported in the Google Play services platform by using the access token to manually make API requests or using a client library provided by the service provider.

Make your games social with Google Play game services. Add achievements, leaderboards, real-time multiplayer, and other popular features using the Google Play game services SDK. Let players sign in using their Google+ identities and share their gaming experience with friends. Visit developers.google.com/games/services for more information about integrating game services into your app.

Allow your users explore the world with rich maps provided by Google. Identify locations with custom markers, augment the map data with image overlays, embed one or more maps as fragments, and much more.

Google Play services powers a broad set of SDKs on Android to help you build your app, enhance privacy and security, engage users, and grow your business. These SDKs are unique in that they only require a thin client library to be included in your app, as shown in figure 1. At runtime, the client library communicates with the bulk of the SDK's implementation and footprint in Google Play services.

Search the world's information, including webpages, images, videos and more. Google has many special features to help you find exactly what you're looking. Google Search, or simply Google, is a web search engine developed by Google LLC. It is the most used search engine on the World Wide Web across all platforms, with 92.16% market share as of December 2020

Google Sign-In is a secure authentication system that reduces the burden of login for your users, by enabling them to sign in with their Google Account—the same account they already use with Gmail, Play, Google+, and other Google services. Google Sign-In is also your gateway to connecting with Google’s users and services in a secure manner. You can give your users the opportunity to pay with Google Pay, share with their Google-wide contacts, save a file to Drive, add an event to Calendar, and more. Integrate Google’s user-centric APIs and services inside your app to help your users take action and convert.

Mono for Android is a runtime and development stack that allows . NET developers to leverage their knowledge of Visual Studio and C# to develop applications for Android-based devices. It interprets the Mono byte code and handles communication with the Dalvik runtime for calls to native Android APIs

OpenTK, also known as The Open Toolkit library, is a C# graphics library superseding the Tao Framework. It provides access to graphics tools contained in OpenGL, OpenCL, and OpenAL to a variety of CLR-based languages Use OpenTK to add cross-platform 3d graphics, audio, compute and haptics to your C# application. Integrate it into your existing user interface or use it standalone without any external dependencies.