.bulbs { max-width: 100%; width: 400px; margin: 0 auto; }

.bulb { float: left; width: 30%; max-width: 100px; margin-right: 3%; margin-bottom: 3%; }

.bulb span { display: block; width: 100%; padding-bottom: 100%; background-image: url('lights.png'); background-repeat: no-repeat; background-position: center center; background-size: contain; border-radius: 50%; }