/* ===========================
   CSS Variables / Theme
   =========================== */
:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --secondary-color: #64748b;
    --danger-color: #dc2626;
    --warning-color: #ea580c;

    --bg-color: #ffffff;
    --bg-gray: #f8fafc;
    --bg-dark: #1e293b;

    --text-primary: #0f172a;
    --text-secondary: #475569;

    --border-color: #e2e8f0;
    --border-radius: 8px;
    --border-radius-lg: 12px;

    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);

    --container-width: 1200px;
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;

    --transition: all 0.2s ease;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-color);
}

/* ===========================
   Typography
   =========================== */
h1, h2, h3, h4, h5, h6 {
    font-weight: 600;
    line-height: 1.2;
    margin-bottom: var(--spacing-sm);
}

h1 { font-size: 2.5rem; }
h2 { font-size: 2rem; }

p {
    margin-bottom: var(--spacing-sm);
    color: var(--text-secondary);
}

a {
    color: var(--primary-color);
    text-decoration: none;
    transition: var(--transition);
}

a:hover {
    color: var(--primary-hover);
}

.small-caps {
    font-variant: small-caps;
    font-weight: 600;
}

/* ===========================
   Container
   =========================== */
.container {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
}

/* ===========================
   Sticky Navigation
   =========================== */
.sticky-nav {
    position: sticky;
    top: 0;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
    z-index: 1000;
    box-shadow: var(--shadow-sm);
}

.nav-container {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: var(--spacing-sm) var(--spacing-lg);
    display: flex;
    gap: var(--spacing-lg);
    justify-content: center;
}

.nav-container a {
    color: var(--text-secondary);
    font-weight: 500;
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--border-radius);
}

.nav-container a:hover {
    color: var(--primary-color);
    background: var(--bg-gray);
}

/* ===========================
   Hero / Header Section
   =========================== */
.hero {
    text-align: center;
    padding: var(--spacing-xl) 0;
    background: linear-gradient(to bottom, var(--bg-gray), var(--bg-color));
}

.title {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: var(--spacing-md);
    line-height: 1.3;
}

.authors {
    font-size: 1.2rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-lg);
    font-weight: 500;
}

.action-buttons {
    display: flex;
    gap: var(--spacing-sm);
    justify-content: center;
    flex-wrap: wrap;
}

/* ===========================
   Buttons
   =========================== */
.btn {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: 0.625rem 1.25rem;
    border: none;
    border-radius: 50px;
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    text-decoration: none;
    background: var(--bg-color);
    color: var(--text-primary);
    box-shadow: var(--shadow);
}

.btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.btn:active {
    transform: translateY(0);
}

.btn-primary {
    background: var(--primary-color);
    color: white;
}

.btn-primary:hover {
    background: var(--primary-hover);
    color: white;
}

.btn-primary:visited {
    color: white;
}

.btn-secondary {
    background: var(--secondary-color);
    color: white;
}

.btn-secondary:hover {
    background: #475569;
}

.btn-danger {
    background: var(--danger-color);
    color: white;
}

.btn-warning {
    background: var(--warning-color);
    color: white;
}

.btn-large {
    padding: 0.875rem 2rem;
    font-size: 1.1rem;
}

.btn-small {
    padding: 0.5rem 1rem;
    font-size: 0.875rem;
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none;
}

.btn:disabled:hover {
    transform: none;
}

.btn-icon {
    font-size: 1.2em;
}

/* ===========================
   Notice Toast
   =========================== */
.notice-container {
    position: fixed;
    top: 84px;
    right: 20px;
    z-index: 1400;
    pointer-events: none;
}

.notice-toast {
    max-width: min(440px, calc(100vw - 40px));
    background: rgba(15, 23, 42, 0.96);
    color: #fff;
    border: 1px solid rgba(148, 163, 184, 0.3);
    border-radius: 12px;
    padding: 12px 14px;
    font-size: 0.9rem;
    line-height: 1.45;
    box-shadow: var(--shadow-lg);
    opacity: 0;
    transform: translateY(-8px);
    transition: opacity 0.22s ease, transform 0.22s ease;
}

.notice-toast.is-visible {
    opacity: 1;
    transform: translateY(0);
}

/* ===========================
   Sections
   =========================== */
.section {
    padding: var(--spacing-xl) 0;
}

.section-gray {
    background: var(--bg-gray);
}

.section-title {
    text-align: center;
    margin-bottom: var(--spacing-md);
    color: var(--text-primary);
}

.section-description {
    text-align: center;
    max-width: 800px;
    margin: 0 auto var(--spacing-lg);
    color: var(--text-secondary);
    font-size: 1.1rem;
}

/* ===========================
   Abstract Section
   =========================== */
#abstract .container {
    max-width: 1100px;
}

.abstract-content {
    max-width: var(--container-width);
    margin: 0 auto;
    background: var(--bg-color);
    padding: var(--spacing-lg);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow);
}

.abstract-content p {
    font-size: 1.05rem;
    line-height: 1.8;
    text-align: justify;
}

.abstract-figure {
    margin-top: var(--spacing-md);
}

.abstract-figure img {
    width: 100%;
    height: auto;
    display: block;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
}

/* ===========================
   Video Samples
   =========================== */
.results-gallery {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--spacing-md);
}

.video-card {
    background: var(--bg-color);
    border-radius: var(--border-radius-lg);
    padding: var(--spacing-md);
    box-shadow: var(--shadow);
    transition: var(--transition);
}

.video-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.video-wrapper {
    position: relative;
    margin-bottom: var(--spacing-sm);
}

.sample-video {
    width: 100%;
    height: auto;
    max-height: 500px;
    display: block;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    background: #000;
    object-fit: contain;
}

.video-label {
    position: absolute;
    top: 6px;
    left: 6px;
    background: rgba(0, 0, 0, 0.7);
    color: #fff;
    font-size: 0.65rem;
    font-weight: 600;
    padding: 2px 6px;
    border-radius: 4px;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    z-index: 2;
    opacity: 0.85;
}

.video-category-row {
    margin-top: var(--spacing-sm);
    padding: 10px 12px;
    background: var(--bg-gray);
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    gap: 10px;
}

.video-category-label {
    font-size: 0.78rem;
    font-weight: 700;
    letter-spacing: 0.04em;
    text-transform: uppercase;
    color: var(--text-secondary);
    flex-shrink: 0;
}

.video-category-tag {
    display: inline-block;
    font-size: 0.88rem;
    font-weight: 700;
    line-height: 1.35;
    color: var(--text-primary);
    background: #fff;
    border: 1px solid var(--border-color);
    border-radius: 999px;
    padding: 4px 10px;
}

.video-missing .video-category-row {
    border-color: #f59e0b;
}

/* ===========================
   Footer
   =========================== */
.footer {
    background: var(--bg-dark);
    color: #fff;
    text-align: center;
    padding: var(--spacing-lg) 0;
    margin-top: var(--spacing-xl);
}

.footer p {
    color: rgba(255, 255, 255, 0.8);
    margin-bottom: var(--spacing-xs);
}

.footer-note {
    font-size: 0.875rem;
    color: rgba(255, 255, 255, 0.6);
}

/* ===========================
   Responsive Design
   =========================== */
@media (max-width: 1024px) {
    .results-gallery {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 768px) {
    :root {
        --spacing-xl: 2rem;
        --spacing-lg: 1.5rem;
    }

    .title {
        font-size: 1.75rem;
    }

    .section-title {
        font-size: 1.5rem;
    }

    .nav-container {
        gap: var(--spacing-sm);
    }

    .results-gallery {
        grid-template-columns: 1fr;
        gap: var(--spacing-sm);
    }

    .notice-container {
        top: 72px;
        right: 12px;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 var(--spacing-sm);
    }

    .title {
        font-size: 1.5rem;
    }

    .action-buttons {
        flex-direction: column;
        align-items: stretch;
    }

    .btn {
        justify-content: center;
    }

    .results-gallery {
        grid-template-columns: 1fr;
    }
}