style.css

*
{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

@keyframes wave {
    0%, 100% {
      transform: translateX(0);
    }
    25% {
      transform: translateX(-15px);
    }
    75% {
        transform: translateX(15px);
      }
}

body {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    padding: 0 0.5rem 0;
    background: whitesmoke;
    font-family: Verdana, Geneva, Tahoma, sans-serif;
    min-width: -moz-fit-content;
    min-width: fit-content;
}

.gif {
    height: 20rem;
    width: 22rem;
}

h2 {
    text-align: center;
    font-size: 1.5em;
    color: #81030b;
    margin: 15px 0;
}
.btn-group {
    width: 100%;
    height: 50px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    margin-top: 50px;
}
button {
    position: absolute;
    width: 150px;
    height: inherit;
    color: white;
    font-size: 1.2em;
    border-radius: 30px;
    outline: none;
    cursor: pointer;
    box-shadow: 0 2px 4px gray;
    border: 2px solid #81030b;
    font-size: 1.2em;
}
button:nth-child(1) {
    margin-left: -200px;
    background: #81030b;
}
button:nth-child(2) {
    margin-right: -200px;
    background: white;
    color: #81030b;
}

.animation{
    animation: wave 0.5s infinite;
}