# Add and return a round button to a default location
	#
	# Fired events use `name`, it should usually correspond to a
	# keyboard key like "space" or "a".
	# `texture` is displayed at the button position, it also sets the
	# touchable surface of the button.
	#
	# If this method is called, it should be after `add_dpad` to
	# avoid overlapping controls.
	#
	# A maximum of 6 buttons may be added using this method when
	# there is less than 2 `DPad`. Otherwise, only 2 buttons can be added.
	fun add_button(name: String, texture: Texture): nullable RoundButton
	do
		if n_dpads == 2 and button_positions.length == 6 then
			# Drop the bottom 4 buttons
			button_positions.remove_at 4
			button_positions.remove_at 3
			button_positions.remove_at 1
			button_positions.remove_at 0
		end

		assert button_positions.not_empty else print_error "Too many buttons in {self}"
		var pos = button_positions.shift
		var but = new RoundButton(
			app.ui_camera.bottom_right.offset(pos.x, pos.y, 0.0), name, texture)
		controls.add but
		return but
	end