html  {
    height: 100%;
}

body {
    opacity: 0;
    font-family: 'Titillium Web';
    margin: 0;
    background-image: url('/static/img/gradient_web 1.png');
    background-size: cover; 
    background-position: center 0; 
    background-repeat: no-repeat;
    -webkit-user-select: none; 
    -ms-user-select: none; 
    user-select: none; 
}

.slim-header {
    width: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    -webkit-user-select: none;
    -ms-user-select: none; 
    user-select: none;
    transition: 0.3s ease;
}

.slim-header:hover {
    transition: 0.3s ease;
    background-color: rgba(0, 0, 0, 1);
}

.link-container {
    margin-left: 10px;
    display: flex;
    justify-content: left;
    align-items: center;
    width: fit-content;
    box-sizing: border-box;
    height: 2.3rem;
}

.slim-header a {
    padding: 0 1em;
    font-size: 0.8rem;
    cursor: pointer;
    color: white;
    transition: 0.1s;
}

.slim-header a:hover {
    color: #00957d;
    transition: 0.1s;
}

.bi-arrow-left-circle {
    font-size: 0.88rem;
    display: inline-block;
    transition: transform 0.3s ease;
}

.back:hover .bi-arrow-left-circle {
    transform: translateX(-5px);
    transition: transform 0.3s ease;
}

.container {
    display: flex;
    margin: auto;
    min-height: calc(100vh - 2.3rem);
    padding: 0 2vw;
}

.intro-container {
    text-align: center;
    margin: 5vh auto 0 auto;
    color: white;
}

.logo {
    width: 400px;
    height: auto;
    display: block;
}

.select-container {
    display: flex;
    flex-direction: column;
    margin: 10vh auto;
    width: 70%;
    gap: 3em;
}

h1 {
    color: white;
    text-align: center;
    font-size: clamp(2vh, 8vw, 6vh);
    padding: 0;
    margin: 0;
}

.year-selection {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 1.5em;
    flex-wrap: wrap;
}

.year-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    flex-direction: column;
    font-weight: 600;
    height: 10rem;
    transition: 0.3s ease;
    font-size: 4rem;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
    border-radius: 0.5rem;
    min-width: 15rem;
    max-width: 15rem;
    text-decoration: none;
    background-color: white;
    color: black;
}

.year-btn:hover {
    transition: 0.3s;
    box-shadow: 5px 10px 10px rgba(0, 0, 0, 0.1);
    transform: rotate3d(15, 5, 5, 10deg) scale(1.05) translateY(-20px);
}

.year-btn:nth-child(odd):hover {
    transition: 0.3s;
    box-shadow: -5px 10px 10px rgba(0, 0, 0, 0.1);
    transform: rotate3d(15, 5, 5, -10deg) scale(1.05) translateY(-20px);;
}

.year-btn.default {
    background-color: #777;
}

.year-btn.default:hover {
    background-color: #555;
}

@keyframes fadeIn {
    from {
        transform: translateY(-20px);
        opacity: 0; 
    }
    to {
        transform: translateY(0);
        opacity: 1;
    }
}