Volume Gamer is a free Android app developed by Sunilkumar Ramamurthy that lets you control any in-game buttons with your hardware volume buttons. It's a personalization app that saves you the expense of buying game triggers or gamepads, as you can use this application to do the same thing for you.

With Volume Gamer, you can configure your volume buttons to click anywhere on the screen. To use the app, you need to provide the 'draw over other apps' and 'accessibility' permissions, then start the service. Drag/drop the '+' and '-' icons anywhere and on any screen. Now, press your hardware volume buttons to click on that part of the screen. You can also long-press the hardware volume buttons to click continuously.

Overall, Volume Gamer is a useful app that allows you to play games more comfortably and efficiently. It's easy to use and doesn't require any complex setup. If you're looking for an app that can help you control your game buttons with hardware volume buttons, give Volume Gamer a try.