Change the texture of the buttons. Sun is set to be default, and it is the only texture to show where you touch on the joystick.
On-screen keyboard size
Change the touchable range of the buttons. It's not recommended to edit it there.
Size of button images
Change the size of button images, won't do anything to the touchable range of a button.
On-screen keyboard transparency
Change the transparency of the button images.
Customize on-screen keyboard layout
It's highly recommended to edit button layout there. You can drag buttons directly, or tap to choose one button, then slide in an empty place to change it's shape. There will be words above to inform you what this button is.
If your texture is not sun, the texture shown in the customize interface will be Simple Theme.
Remap on-screen controls
There are 7 buttons and 2 joysticks in total. You can't remap Text input button and joysticks. It's highly recommended to turn off the Joystick1, or you can't jump while running, or start to run without jumping. To turn off it, tap into the option and follow the picture.