/* ============================================
   SKYE — Personal Website Stylesheet
   Dark. Clean. Depth.
   ============================================ */

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

:root {
    --bg-primary: #0a0a0f;
    --bg-secondary: #12121a;
    --bg-card: #16161f;
    --text-primary: #e0dde6;
    --text-secondary: #9590a8;
    --text-muted: #5c5775;
    --accent: #7c5cbf;
    --accent-glow: #9b7ad8;
    --accent-dim: #4a3570;
    --border: #1e1e2a;
    --font-body: 'Georgia', 'Times New Roman', serif;
    --font-heading: 'Helvetica Neue', 'Arial', sans-serif;
    --font-mono: 'SF Mono', 'Fira Code', monospace;
    --max-width: 780px;
}

html {
    font-size: 17px;
    scroll-behavior: smooth;
}

body {
    background-color: var(--bg-primary);
    color: var(--text-primary);
    font-family: var(--font-body);
    line-height: 1.75;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}


/* --- Navigation --- */
.main-nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem 2rem;
    border-bottom: 1px solid var(--border);
    background: var(--bg-secondary);
    position: sticky;
    top: 0;
    z-index: 100;
    backdrop-filter: blur(10px);
}

.nav-logo {
    font-family: var(--font-heading);
    font-size: 1.4rem;
    font-weight: 700;
    color: var(--accent-glow);
    text-decoration: none;
    letter-spacing: 0.05em;
}

.nav-links {
    display: flex;
    gap: 1.8rem;
}

.nav-links a {
    color: var(--text-secondary);
    text-decoration: none;
    font-family: var(--font-heading);
    font-size: 0.85rem;
    letter-spacing: 0.04em;
    text-transform: uppercase;
    transition: color 0.3s ease;
}

.nav-links a:hover,
.nav-links a.active {
    color: var(--accent-glow);
}


/* --- Hero Section (index) --- */
.hero {
    text-align: center;
    padding: 6rem 2rem 4rem;
    background: radial-gradient(ellipse at 50% 0%, var(--accent-dim) 0%, transparent 60%);
}

.hero h1 {
    font-family: var(--font-heading);
    font-size: 3.2rem;
    font-weight: 300;
    color: var(--text-primary);
    letter-spacing: 0.08em;
    margin-bottom: 0.5rem;
}

.hero .tagline {
    font-size: 1.1rem;
    color: var(--text-secondary);
    font-style: italic;
    margin-bottom: 2rem;
}

.hero .intro {
    max-width: var(--max-width);
    margin: 0 auto;
    font-size: 1.05rem;
    color: var(--text-secondary);
    line-height: 1.85;
}

/* --- Section Headers --- */
.section-header {
    text-align: center;
    padding: 4rem 2rem 2rem;
}

.section-header h1 {
    font-family: var(--font-heading);
    font-size: 2.4rem;
    font-weight: 300;
    letter-spacing: 0.06em;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.section-subtitle {
    font-size: 1rem;
    color: var(--text-secondary);
    font-style: italic;
    max-width: 600px;
    margin: 0 auto;
}

/* --- Page Content --- */
.page-content {
    flex: 1;
}

.content-body {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 1rem 2rem 4rem;
}

/* --- Category Cards (index) --- */
.categories {
    max-width: 900px;
    margin: 0 auto;
    padding: 2rem;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 1.5rem;
}

.category-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 2rem;
    text-decoration: none;
    color: inherit;
    transition: border-color 0.3s ease, transform 0.2s ease;
}

.category-card:hover {
    border-color: var(--accent);
    transform: translateY(-2px);
}

.category-card h3 {
    font-family: var(--font-heading);
    font-size: 1.15rem;
    color: var(--accent-glow);
    margin-bottom: 0.5rem;
    letter-spacing: 0.03em;
}

.category-card p {
    font-size: 0.92rem;
    color: var(--text-secondary);
    line-height: 1.7;
}

/* --- Articles / Entries --- */
.entry {
    margin-bottom: 3rem;
    padding-bottom: 3rem;
    border-bottom: 1px solid var(--border);
}

.entry:last-of-type {
    border-bottom: none;
}

.entry time {
    font-family: var(--font-mono);
    font-size: 0.78rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.08em;
}

.entry h2 {
    font-family: var(--font-heading);
    font-size: 1.5rem;
    font-weight: 400;
    color: var(--text-primary);
    margin: 0.4rem 0 1rem;
}

.entry p {
    margin-bottom: 1rem;
    color: var(--text-secondary);
}

/* --- Paper Cards (papers index) --- */
.papers-grid {
    max-width: 960px;
    margin: 0 auto;
    padding: 1rem 2rem 4rem;
    display: grid;
    grid-template-columns: 1fr;
    gap: 2.5rem;
}

.paper-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 10px;
    overflow: hidden;
    text-decoration: none;
    color: inherit;
    transition: border-color 0.3s ease, transform 0.2s ease, box-shadow 0.3s ease;
    display: block;
}

.paper-card:hover {
    border-color: var(--accent);
    transform: translateY(-3px);
    box-shadow: 0 8px 32px rgba(124, 92, 191, 0.15);
}

.paper-card-image {
    width: 100%;
    height: 240px;
    object-fit: cover;
    display: block;
    border-bottom: 1px solid var(--border);
}

.paper-card-body {
    padding: 1.8rem 2rem;
}

.paper-card-body time {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.08em;
}

.paper-card-body h2 {
    font-family: var(--font-heading);
    font-size: 1.35rem;
    font-weight: 400;
    color: var(--text-primary);
    margin: 0.5rem 0 0.8rem;
    line-height: 1.4;
}

.paper-card-body .paper-author {
    font-family: var(--font-mono);
    font-size: 0.8rem;
    color: var(--accent-glow);
    margin-bottom: 0.8rem;
}

.paper-card-body p {
    font-size: 0.92rem;
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: 0.8rem;
}

.paper-card-body .paper-status {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    color: var(--text-muted);
    font-style: italic;
}

.paper-section-label {
    font-family: var(--font-heading);
    font-size: 0.85rem;
    color: var(--accent-glow);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    margin-bottom: 1.5rem;
    padding-bottom: 0.5rem;
    border-bottom: 1px solid var(--border);
    max-width: 960px;
    margin-left: auto;
    margin-right: auto;
    padding-left: 2rem;
    padding-right: 2rem;
}

/* --- Paper page cover image --- */
.paper-cover {
    width: 100%;
    max-width: var(--max-width);
    margin: 0 auto 2rem;
    display: block;
    border-radius: 8px;
    border: 1px solid var(--border);
}

/* --- About Page --- */
.about-content .about-block {
    margin-bottom: 2.5rem;
}

.about-block h2 {
    font-family: var(--font-heading);
    font-size: 1.3rem;
    font-weight: 400;
    color: var(--accent-glow);
    margin-bottom: 0.8rem;
}

.about-block p {
    color: var(--text-secondary);
    margin-bottom: 0.8rem;
}

.interests-list {
    list-style: none;
    padding: 0;
}

.interests-list li {
    padding: 0.5rem 0;
    color: var(--text-secondary);
    border-bottom: 1px solid var(--border);
}

.interests-list li:last-child {
    border-bottom: none;
}

.interests-list strong {
    color: var(--text-primary);
}

/* --- Coming Soon --- */
.coming-soon {
    text-align: center;
    padding: 2rem;
    border: 1px dashed var(--border);
    border-radius: 8px;
    margin-top: 2rem;
}

.coming-soon p {
    color: var(--text-muted);
    font-style: italic;
    font-size: 0.92rem;
}

/* --- Footer --- */
.main-footer {
    text-align: center;
    padding: 2rem;
    border-top: 1px solid var(--border);
    background: var(--bg-secondary);
}

.main-footer p {
    font-family: var(--font-heading);
    font-size: 0.8rem;
    color: var(--text-muted);
    letter-spacing: 0.04em;
}

/* --- Responsive --- */
@media (max-width: 640px) {
    .main-nav {
        flex-direction: column;
        gap: 1rem;
    }

    .nav-links {
        flex-wrap: wrap;
        justify-content: center;
        gap: 1rem;
    }

    .hero h1 {
        font-size: 2.2rem;
    }

    .categories {
        grid-template-columns: 1fr;
    }

    .paper-card-image {
        height: 180px;
    }

    .paper-card-body {
        padding: 1.2rem 1.5rem;
    }

    .paper-card-body h2 {
        font-size: 1.15rem;
    }
}

/* --- Intellectual Property License Block --- */
.ip-license {
    background: var(--bg-secondary);
    border: 1px solid var(--accent-dim);
    border-radius: 6px;
    padding: 1.5rem 2rem;
    margin: 2rem auto;
    max-width: var(--max-width);
    font-family: var(--font-mono);
    font-size: 0.75rem;
    line-height: 1.7;
    color: var(--text-muted);
}

.ip-license strong {
    color: var(--accent-glow);
    font-size: 0.8rem;
    display: block;
    margin-bottom: 0.5rem;
    letter-spacing: 0.06em;
}

.ip-license a {
    color: var(--accent-glow);
    text-decoration: none;
}

.ip-license a:hover {
    text-decoration: underline;
}