/* Reset & Base styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    background-color: var(--color-dark);
    color: var(--color-text);
    font-family: 'Noto Sans JP', sans-serif;
    line-height: 1.6;
}

/* Animation Keyframes */
@keyframes gradientRotate {
    0% {
        transform: rotate(0deg);
    }
    100% {
        transform: rotate(360deg);
    }
}

/* Layout */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
.site-header {
    padding: 20px 0;
    position: relative;
    z-index: 100;
}

/* Main Visual */
.main-visual {
    position: relative;
    height: 100vh;
    min-height: 600px;
    display: flex;
    align-items: center;
    justify-content: center;
    overflow: hidden;
}

.gradient-circle {
    position: absolute;
    width: 800px;
    height: 800px;
    background: linear-gradient(45deg, 
        var(--color-primary),
        var(--color-secondary),
        var(--color-accent),
        var(--color-highlight)
    );
    border-radius: 50%;
    animation: gradientRotate 20s linear infinite;
}

/* Cards */
.seminar-card {
    background: rgba(0, 0, 0, 0.7);
    border-radius: 10px;
    padding: 20px;
    margin-bottom: 30px;
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.1);
}

.seminar-card__title {
    color: var(--color-primary);
    margin-bottom: 15px;
}

.seminar-card__image {
    width: 100%;
    height: 200px;
    object-fit: cover;
    border-radius: 5px;
    margin-bottom: 15px;
}

/* Navigation dots */
.nav-dots {
    display: flex;
    justify-content: center;
    gap: 10px;
    margin: 30px 0;
}

.nav-dot {
    width: 12px;
    height: 12px;
    border-radius: 50%;
    background: var(--color-text);
    opacity: 0.3;
    cursor: pointer;
    transition: opacity 0.3s ease;
}

.nav-dot.active {
    opacity: 1;
}

/* Responsive */
@media (max-width: 768px) {
    .gradient-circle {
        width: 400px;
        height: 400px;
    }
    
    .container {
        padding: 0 15px;
    }
}

/* ページトップへ戻るボタン */
#page-top-btn {
    position: fixed;
    bottom: 20px;
    right: 20px;
    z-index: 999;
    display: none; /* JSで制御 */
    width: 50px;
    height: 50px;
    background-color: #333;
    color: #fff;
    border-radius: 50%;
    text-align: center;
    line-height: 50px;
    font-size: 20px;
    transition: background-color 0.3s;
}

#page-top-btn:hover {
    background-color: #555;
}