Refactoring MainActivity to BulletHellActivity
As in the previous projects, MainActivity is a bit vague, so let's refactor MainActivity to BulletHellActivity.
In the project panel, right-click the MainActivity file and select Refactor | Rename. In the pop-up window, change MainActivity to BulletHellActivity. Leave all the other options as the defaults and left-click the Refactor button.
Notice the filename in the project panel has changed, as expected, but also multiple occurrences of MainActivity have been changed to BulletHellActivity in the AndroidManifest.xml file, as well as an instance in the BulletHellActivity.java file.
Let's set the screen orientation.
