old_btns

function am_bigbutton( $atts, $content = null ) {
 	//[big-button color="" link=""][/big-button]
	extract(shortcode_atts(array(
		"color" => 'yellow',
		"link" => '#'
	), $atts));

	return '<a href="'.$atts['link'].'" class="big-button '.$atts['color'].'">'.$content.'</a>';
}
add_shortcode('big-button', 'am_bigbutton');

function am_mediumbutton( $atts, $content = null ) {
 	//[medium-button color="" link=""][/medium-button]
	extract(shortcode_atts(array(
		"color" => 'yellow',
		"link" => '#'
	), $atts));

	return '<a href="'.$atts['link'].'" class="medium-button '.$atts['color'].'">'.$content.'</a>';
}
add_shortcode('medium-button', 'am_mediumbutton');

//small button
function am_smallbutton( $atts, $content = null ) {
 	//[small-button color="" link=""][/small-button]
	extract(shortcode_atts(array(
		"color" => 'yellow',
		"link" => '#'
	), $atts));

	return '<a href="'.$atts['link'].'" class="small-button '.$atts['color'].'">'.$content.'</a>';
}
add_shortcode('small-button', 'am_smallbutton');