style.css

@import url('https://fonts.googleapis.com/css2?family=Noto+Serif+JP:wght@200&display=swap');

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Noto Serif JP', serif;
}
body {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-image: url('img/background.jpeg');
    background-size: cover;  
}
.gradient-text {
    background-color: red;
    background-image: linear-gradient(45deg, #f3ec78, #af4261);
    background-size: 100%;
    background-repeat: repeat;
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent; 
    -moz-background-clip: text;
    -moz-text-fill-color: transparent;
}
.box {
    position: relative;
    width: 230px;
    height: 300px;
    display: flex;
    justify-content: center;
    align-items: center;
    background: rgba(0, 0, 0, 0.5);
    overflow: hidden;
    border-radius: 20px;
}
.box::before {
    content: '';
    position: absolute;
    width: 150px;
    height: 500px;
    background: linear-gradient(114.92542058625486deg, rgba(224, 247, 135,1) 5.736111111111111%,rgba(78, 227, 250,1) 96.29166666666666%);
    animation: animate 4s linear infinite;
}
.box::after {
    content: '';
    position: absolute;
    inset: 4px;
    background: linear-gradient(114.92542058625486deg, rgba(10, 83, 122,1) 5.736111111111111%,rgba(129, 209, 201,1) 96.29166666666666%);
    border-radius: 16px;
}
@keyframes animate
{
    0% {
        transform: rotate(0deg);
    }
    0% {
        transform: rotate(360deg);
    }
}
.box h2 {
    position: relative;
    font-size: 5em;
    z-index: 10;
    writing-mode: vertical-rl;
}