Raspberry Pi Zero Dedicated Console Answered

I have written a small 15 Puzzle game in Java—the only programming language I am fully comfortable with. I’m satisfied with the game itself and would like it to have a simple platform on which to play it rather than it just being a .jar on my computer. I would like to make a small handheld with raspberry pi zero just to run the game on boot and let that be that. I plan to use a usb encoder to map the buttons, so I don’t have to worry about programming the gpios with Java (as I have found this to be a bit of a hassle). I would love any ideas or assistance regarding the best way to play the Java program on boot and maybe a way to effectively shut down the handheld without potentially corrupting my microsd. Any other neat ideas or tips for the project are also, of course, quite welcome. Thank you!