sub mousebuttondown {
	my $self	= shift;
	my $event	= shift;
	my $app		= $self->app();
	
	say "mousebutton";
	say '<' . $event->button_x() . ',' . $event->button_x() . '>';

	my $r_width  = 10;
	my $r_height = 10;
	my $rect = SDL::Rect->new(
		-height => $r_height,
		-width  => $r_width,
		-x      => $event->button_x() - $r_width/2,
		-y      => $event->button_y() - $r_height/2,
	);
	
	my $color = SDL::Color->new(
		-r => 0x00,
		-g => 0x00,
		-b => 0xff,
	);
	
	$app->fill( $rect, $color );
	
	$app->update( $rect );

} # /mousebuttondown