One of the most-played multiplayer games Counter Strike can now be played on Android. A coder named Alibek Omarev has programmed the Android version and put it on GitHub.
The version you can play on the Android phones is the classic Counter-Strike 1.6. The latest version of the game is Counter-Strike: Global Offensive, an online global multiplayer game, although the installation is not as straightforward as installing any app. After downloading the APK (Android installable) file, you have to install Xash3D engine. All these files are available here.
Omarev has also posted a video of the gameplay. Surely there are some lags in the video but it is decent for a mobile to handle all the graphics and processing.
However, you are getting a full PC version experience on the mobile phone. You can access and set up servers as well. A lot of keyboard shortcuts from the PC version are now presented as virtual buttons in the Android version. These buttons are fully customizable as the developer explained on Reddit.
The trend of PC games ported to mobile is not new. In the past games like FIFA, Half-Life and GTA have had official mobile versions of the games released by the studios.