/* Modern Academic Website CSS - Mobile First Design */

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

:root {
    --primary-color: #2c3e50;
    --accent-color: #3498db;
    --text-color: #333;
    --text-light: #666;
    --bg-color: #fff;
    --bg-gray: #f8f9fa;
    --border-color: #e1e8ed;
    --transition: all 0.3s ease;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background: var(--bg-color);
    font-size: 16px;
}

/* Container */
.container {
    width: 100%;
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 20px;
}

@media (min-width: 768px) {
    .container {
        padding: 0 40px;
    }
}

/* Navigation */
.navbar {
    position: sticky;
    top: 0;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.05);
    z-index: 1000;
    padding: 1rem 0;
}

.navbar .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-brand {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--primary-color);
}

.nav-toggle {
    display: flex;
    flex-direction: column;
    gap: 4px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
}

.nav-toggle span {
    width: 25px;
    height: 2px;
    background: var(--primary-color);
    transition: var(--transition);
}

.nav-menu {
    list-style: none;
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: var(--bg-color);
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.1);
    padding: 1rem 0;
}

.nav-menu.active {
    display: block;
}

.nav-menu li {
    padding: 0.5rem 20px;
}

.nav-menu a {
    text-decoration: none;
    color: var(--text-color);
    font-size: 0.95rem;
    transition: var(--transition);
    display: block;
    padding: 0.5rem 0;
}

.nav-menu a:hover {
    color: var(--accent-color);
}

@media (min-width: 768px) {
    .nav-toggle {
        display: none;
    }

    .nav-menu {
        display: flex !important;
        position: static;
        flex-direction: row;
        gap: 2rem;
        box-shadow: none;
        padding: 0;
        background: transparent;
    }

    .nav-menu li {
        padding: 0;
    }

    .nav-menu a {
        padding: 0;
    }
}

/* Hero Section */
.hero {
    padding: 1.5rem 0;
    background: url('../assets/img/background.jpeg') center center / cover no-repeat;
    position: relative;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(255, 255, 255, 0.6);
    z-index: 0;
}

.hero .container {
    position: relative;
    z-index: 1;
}

.hero-content {
    text-align: center;
}

.profile-img-wrapper {
    position: relative;
    width: 150px;
    height: 150px;
    margin: 0 auto 1rem;
    border-radius: 50%;
    overflow: hidden;
    border: 4px solid white;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
}

.profile-img {
    position: absolute;
    inset: 0;
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: opacity 0.3s cubic-bezier(0.2, 0, 0, 1);
}

.profile-img-hover {
    opacity: 0;
}

@media (hover: hover) {
    .profile-img-wrapper:hover .profile-img-default {
        opacity: 0;
    }

    .profile-img-wrapper:hover .profile-img-hover {
        opacity: 1;
    }
}

.hero h1 {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.chinese-name {
    font-weight: 400;
    font-size: 0.9em;
    color: var(--text-light);
}

.subtitle {
    font-size: 1.1rem;
    color: var(--text-light);
    margin-bottom: 1.5rem;
}

.social-links {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin-top: 1rem;
}

.social-links a {
    width: 45px;
    height: 45px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: white;
    border-radius: 50%;
    color: var(--primary-color);
    font-size: 1.3rem;
    transition: var(--transition);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

.social-links a:hover {
    transform: translateY(-3px);
    box-shadow: 0 4px 12px rgba(52, 152, 219, 0.3);
    color: var(--accent-color);
}

@media (min-width: 768px) {
    .hero {
        padding: 1.75rem 0;
    }

    .profile-img-wrapper {
        width: 180px;
        height: 180px;
    }

    .hero h1 {
        font-size: 2rem;
    }

    .subtitle {
        font-size: 1.2rem;
    }
}

/* Sections */
.section {
    padding: 2rem 0;
}

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

.section-title {
    font-size: 1.8rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 2rem;
    padding-bottom: 0.75rem;
    border-bottom: 3px solid var(--accent-color);
    display: inline-block;
}

@media (min-width: 768px) {
    .section {
        padding: 2.75rem 0;
    }

    .section-title {
        font-size: 2.2rem;
    }
}

/* Content Styles */
.content {
    line-height: 1.8;
    max-width: 900px;
}

.content p {
    margin-bottom: 1rem;
}

.content h3 {
    color: var(--primary-color);
    margin-top: 2rem;
    margin-bottom: 1rem;
    font-size: 1.3rem;
}

.content h4 {
    color: var(--primary-color);
    margin-top: 1.5rem;
    margin-bottom: 0.75rem;
    font-size: 1.1rem;
}

.content a {
    color: var(--accent-color);
    text-decoration: none;
    transition: var(--transition);
}

.content a:hover {
    text-decoration: underline;
}

.content ul {
    padding-left: 1.5rem;
    margin-bottom: 1rem;
}

.content strong {
    color: var(--primary-color);
    font-weight: 600;
}

/* Projects Grid */
.projects-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 2rem;
    margin-top: 2rem;
}

@media (min-width: 768px) {
    .projects-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: 2.5rem;
    }
}

.project-card {
    background: white;
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.08);
    transition: var(--transition);
    display: flex;
    flex-direction: column;
}

.project-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.15);
}

.project-card img {
    width: 100%;
    height: 200px;
    object-fit: cover;
    display: block;
}

.project-info {
    padding: 1.5rem;
    flex: 1;
    display: flex;
    flex-direction: column;
}

.project-info h3 {
    font-size: 1.1rem;
    color: var(--primary-color);
    margin-bottom: 0.75rem;
    line-height: 1.4;
}

.project-tags {
    color: var(--text-light);
    font-size: 0.85rem;
    margin-bottom: 1rem;
    font-style: italic;
}

.btn-link {
    color: var(--accent-color);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
    margin-top: auto;
    display: inline-block;
}

.btn-link:hover {
    color: var(--primary-color);
    transform: translateX(3px);
}

/* Footer */
.footer {
    background: var(--primary-color);
    color: white;
    padding: 3rem 0 2rem;
    text-align: center;
}

.footer-content {
    max-width: 700px;
    margin: 0 auto;
}

.footer p {
    margin-bottom: 1.5rem;
    line-height: 1.7;
}

.footer .social-links {
    margin: 2rem 0;
}

.footer .social-links a {
    background: rgba(255, 255, 255, 0.1);
    color: white;
}

.footer .social-links a:hover {
    background: white;
    color: var(--primary-color);
}

.footer-note {
    font-size: 0.9rem;
    color: rgba(255, 255, 255, 0.8);
}

.copyright {
    font-size: 0.85rem;
    color: rgba(255, 255, 255, 0.6);
    margin-top: 1rem;
}

/* Responsive Images */
img {
    max-width: 100%;
    height: auto;
}

/* Smooth transitions */
a, button {
    transition: var(--transition);
}