floating.kv

<CustomButton@Button>:
	font_size: 32
	color: 0, 0, 0, 1
	background_normal: 'normal-color.png'
	background_down: 'down-color.png'
	background_color: .88, .88, .88, 1
	border: 30,30,30,30
	size_hint: .3, .1

<RoundedButton@Button>:
	font_size: 32
    background_color: 0,0,0,0  # the last zero is the critical on, make invisible
    size_hint: .3, .1
    canvas.before:
        Color:
            rgba: (.4,.4,.4,1) if self.state=='normal' else (0,.7,.7,1)  # visual feedback of press
        RoundedRectangle:
            pos: self.pos
            size: self.size
            radius: [10,]
	
<FloatLayout>:
	RoundedButton:
		text: "Top Left"
		pos_hint: {"x": 0, "top": 1}
	CustomButton:
		text: "Bottom Right??"
		pos_hint: {"right": 1, "y": 0}
	CustomButton:
		text: "Top Right"
		pos_hint: {"right": 1, "top": 1}
	CustomButton:
		text: "Bottom Left"
		pos_hint: {"left": 1, "bottom": 0}
	CustomButton:
		text: "Center"
		pos_hint: {"center_x": .5, "center_y": .5}