SoftKeyZ from the developer Janis Elfert. Perhaps you have been looking for such a program for your Android the device with which you can customize according to your taste and mood, functional and navigational buttons. SoftKeyZ will offer you over 150 skins such buttons, but if you haven't found something that suits you, it is possible to import the desired skin. If necessary, you can restore the original look of the buttons by tapping on "Apply Backup".