Unity is a cross platform engine designed to make it simple for developers to write code once and deploy to many different environments. The release of the free version of Unity 5 means that there is now another reason to consider using the engine to develop future projects.
Instructions for getting the Unity SDK setup for Android development can be found here: http://docs.unity3d.com/Manual/android-sdksetup.html
Previous versions of Unity are known to have issues when deploying to Android Lollipop. Changing setting, such as the version of OpenGL, can offer solutions. It is best to make sure that applications are running the latest version of the engine.
Archived downloads can be found here: http://unity3d.com/get-unity/download/archive
Keywords: Unity, OpenGL, Lollipop, engine