Heart beat animation in applied animation count

HTML-CSS
1

i am bit confused about the width and height property. why do we need to specify them in both ::after and ::before heart pseudo elements ?

.back { position: fixed; padding: 0; margin: 0; top: 0; left: 0; width: 100%; height: 100%; background: white; animation-name: backdiv; animation-duration: 1s; } .heart { position: absolute; margin: auto; top: 0; right: 0; bottom: 0; left: 0; background-color: pink; height: 50px; width: 50px; transform: rotate(-45deg); animation-name: beat; animation-duration: 1s; } .heart:after { background-color: pink; content: ""; border-radius: 50%; position: absolute; width: 50px; height: 50px; top: 0px; left: 25px; } .heart:before { background-color: pink; content: ""; border-radius: 50%; position: absolute; width: 50px; height: 50px; top: -25px; left: 0px; } @keyframes backdiv { 50% { background: #ffe6f2; } } @keyframes beat { 0% { transform: scale(1) rotate(-45deg); } 50% { transform: scale(0.6) rotate(-45deg); } }
2

Go head and edit your post to format your code and post a link to the exercise.