/* Dark / light theme */

[data-theme="dark"] {
    --text-color: #f1f5f9;
    --text-light: #94a3b8;
    --background-light: #334155;
    --white: #1e293b;
    --bg-body: #0f172a;
    --bg-surface: #1e293b;
    --bg-input: #334155;
    --border-subtle: rgba(255, 255, 255, 0.08);
    --border-input: #475569;
    --navbar-bg: rgba(15, 23, 42, 0.96);
    --shadow-nav: 0 2px 16px rgba(0, 0, 0, 0.45);
    --shadow-card: 0 5px 24px rgba(0, 0, 0, 0.35);
    --section-gradient: linear-gradient(135deg, #1e293b 0%, #0f172a 100%);
    --pill-bg: rgba(96, 165, 250, 0.15);
    --nav-hover-bg: rgba(96, 165, 250, 0.12);
}

.navbar {
    background: var(--navbar-bg) !important;
    box-shadow: var(--shadow-nav) !important;
    transition: background-color 0.3s ease, box-shadow 0.3s ease;
}

/* Theme toggle button */
.theme-toggle {
    width: 42px;
    height: 42px;
    border: 1px solid var(--border-subtle);
    border-radius: 50%;
    background: var(--bg-surface);
    color: var(--text-color);
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    font-size: 1.1rem;
    transition: all 0.3s ease;
    flex-shrink: 0;
}

.theme-toggle:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
    transform: translateY(-2px);
    box-shadow: var(--shadow-card);
}

.theme-toggle .fa-sun {
    display: none;
}

[data-theme="dark"] .theme-toggle .fa-moon {
    display: none;
}

[data-theme="dark"] .theme-toggle .fa-sun {
    display: inline-block;
}

/* Section backgrounds */
[data-theme="dark"] .hero,
[data-theme="dark"] .skills,
[data-theme="dark"] .expertise,
[data-theme="dark"] .projects,
[data-theme="dark"] .awards,
[data-theme="dark"] .education {
    background: var(--section-gradient);
}

[data-theme="dark"] .services,
[data-theme="dark"] .publications,
[data-theme="dark"] .contact {
    background: var(--bg-body);
}

/* Cards & surfaces */
[data-theme="dark"] .service-card,
[data-theme="dark"] .project-card,
[data-theme="dark"] .publication-card,
[data-theme="dark"] .award-card,
[data-theme="dark"] .education-card,
[data-theme="dark"] .skill-item,
[data-theme="dark"] .platform-card,
[data-theme="dark"] .icpc-card,
[data-theme="dark"] .timeline-item,
[data-theme="dark"] .stat-item,
[data-theme="dark"] .awards-stats,
[data-theme="dark"] .contact-form,
[data-theme="dark"] .award-lightbox-dialog {
    background: var(--bg-surface);
}

[data-theme="dark"] .award-card-text-only {
    background: linear-gradient(135deg, var(--bg-surface) 0%, #334155 100%);
    border-color: rgba(96, 165, 250, 0.2);
}

[data-theme="dark"] .award-media {
    background: var(--background-light);
    border-color: var(--border-subtle);
}

[data-theme="dark"] .project-card {
    background: rgba(30, 41, 59, 0.95);
    border: 1px solid var(--border-subtle);
}

[data-theme="dark"] .tech-tag,
[data-theme="dark"] .skill-pill {
    background: var(--pill-bg);
    color: #93c5fd;
}

[data-theme="dark"] .category-btn {
    background: var(--bg-surface);
    color: var(--text-color);
}

[data-theme="dark"] .category-btn.active,
[data-theme="dark"] .category-btn:hover {
    color: #fff;
}

[data-theme="dark"] .form-input,
[data-theme="dark"] .form-group input,
[data-theme="dark"] .form-group textarea,
[data-theme="dark"] .chat-input {
    background: var(--bg-input);
    border-color: var(--border-input);
    color: var(--text-color);
}

[data-theme="dark"] .form-input:focus,
[data-theme="dark"] .form-group input:focus,
[data-theme="dark"] .form-group textarea:focus {
    background: var(--bg-surface);
}

[data-theme="dark"] .nav-menu {
    background: var(--bg-surface);
}

[data-theme="dark"] .nav-link:hover,
[data-theme="dark"] .nav-link.active {
    background: var(--nav-hover-bg);
}

[data-theme="dark"] .social-button {
    background: var(--bg-surface);
}

[data-theme="dark"] .education-major,
[data-theme="dark"] .project-badge {
    background: var(--pill-bg);
    color: #93c5fd;
}

[data-theme="dark"] .icpc-stats .stat,
[data-theme="dark"] .awards-stats .stat-item {
    background: var(--pill-bg);
}

[data-theme="dark"] .footer {
    background: #020617;
}

/* Chatbot */
[data-theme="dark"] .chat-window {
    background: var(--bg-surface);
    box-shadow: 0 10px 40px rgba(0, 0, 0, 0.5);
}

[data-theme="dark"] .chat-messages {
    background: var(--bg-body);
}

[data-theme="dark"] .message.bot .message-content {
    background: #1e3a5f;
    color: #93c5fd;
}

[data-theme="dark"] .message.user .message-content {
    background: var(--primary-color);
    color: #fff;
}

[data-theme="dark"] .award-lightbox-backdrop {
    background: rgba(0, 0, 0, 0.9);
}

[data-theme="dark"] .award-lightbox-caption {
    color: var(--text-color);
}

@media (max-width: 1024px) {
    .nav-menu .theme-toggle-wrap {
        width: 100%;
        display: flex;
        justify-content: center;
        padding: 0.5rem 0;
    }
}

/* Featured book chapter */
.book-feature {
    background: var(--bg-surface);
    border-radius: 16px;
    padding: 1.5rem;
    margin-bottom: 2.5rem;
    box-shadow: var(--shadow-card);
    border: 1px solid var(--border-subtle);
}

.book-feature-content {
    margin-bottom: 1.5rem;
}

.book-images-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1.5rem;
}

.book-image-card {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.book-image-media {
    width: 100%;
    min-height: 200px;
}

.book-image-label {
    text-align: center;
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-light);
    margin: 0;
}

.book-detail {
    font-size: 0.9rem;
    color: var(--text-light);
    line-height: 1.6;
    margin-bottom: 0.5rem;
}

.book-detail a {
    color: var(--primary-color);
    word-break: break-all;
}

[data-theme="dark"] .book-detail a {
    color: #93c5fd;
}

.book-badge {
    display: inline-block;
    padding: 0.35rem 0.85rem;
    background: var(--pill-bg);
    color: var(--primary-color);
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
}

[data-theme="dark"] .book-badge {
    color: #93c5fd;
}

.book-feature-content h3 {
    font-size: 1.25rem;
    line-height: 1.4;
    color: var(--text-color);
    margin-bottom: 0.5rem;
}

.book-chapter-title {
    font-size: 1.05rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

[data-theme="dark"] .book-chapter-title {
    color: #93c5fd;
}

.book-meta {
    color: var(--text-light);
    font-size: 0.9rem;
    margin-bottom: 0.75rem;
}

.book-summary {
    color: var(--text-light);
    line-height: 1.7;
    margin-bottom: 1rem;
}

.book-link {
    font-weight: 600;
}

.publications-subheading {
    font-size: 1.35rem;
    color: var(--text-color);
    margin-bottom: 1.5rem;
    text-align: center;
    font-weight: 600;
}

@media (max-width: 900px) {
    .book-images-grid {
        grid-template-columns: 1fr;
        max-width: 320px;
        margin: 0 auto;
    }
}

@media (max-width: 768px) {
    .book-images-grid {
        max-width: 100%;
    }
}