Apparently, you can't restart the battle or go back to the menu when you die if you use the dpad or joystick on the android version. No matter what buttons you press, you cannot select the restart option or go back to the main menu. You have to close the game and open it again to be able to restart the battle. You can, however, press the buttons to restart the battle or go back to the main menu if you use the finger control, which is also a bit buggy to control.