/* ============================================
   Stella Cho Portfolio - Modern CSS
   ============================================ */

/* CSS Variables */
:root {
    --primary: #6366f1;
    --primary-dark: #4f46e5;
    --primary-light: #a5b4fc;
    --secondary: #0ea5e9;
    --accent: #f59e0b;
    --dark: #1e1b4b;
    --dark-light: #312e81;
    --gray-900: #111827;
    --gray-800: #1f2937;
    --gray-700: #374151;
    --gray-600: #4b5563;
    --gray-500: #6b7280;
    --gray-400: #9ca3af;
    --gray-300: #d1d5db;
    --gray-200: #e5e7eb;
    --gray-100: #f3f4f6;
    --gray-50: #f9fafb;
    --white: #ffffff;
    --gold: #fbbf24;
    --gradient: linear-gradient(135deg, #6366f1 0%, #0ea5e9 100%);
    --gradient-text: linear-gradient(135deg, #6366f1 0%, #ec4899 50%, #f59e0b 100%);
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-md: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);
    --shadow-xl: 0 25px 50px -12px rgb(0 0 0 / 0.25);
    --radius-sm: 0.375rem;
    --radius: 0.5rem;
    --radius-md: 0.75rem;
    --radius-lg: 1rem;
    --radius-xl: 1.5rem;
    --radius-full: 9999px;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', 'Noto Sans KR', -apple-system, BlinkMacSystemFont, sans-serif;
    line-height: 1.7;
    color: var(--gray-800);
    background: var(--gray-50);
    overflow-x: hidden;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.3;
    color: var(--gray-900);
}

h1 { font-size: clamp(2rem, 5vw, 3.5rem); }
h2 { font-size: clamp(1.75rem, 4vw, 2.5rem); }
h3 { font-size: clamp(1.25rem, 3vw, 1.5rem); }
h4 { font-size: 1.125rem; }

p {
    color: var(--gray-600);
}

a {
    color: inherit;
    text-decoration: none;
    transition: all 0.3s ease;
}

/* ============================================
   Header & Navigation
   ============================================ */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--gray-200);
    z-index: 1000;
}

.nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1280px;
    margin: 0 auto;
    padding: 1rem 2rem;
}

.logo {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--dark);
}

.nav-links {
    display: flex;
    list-style: none;
    gap: 2rem;
}

.nav-links a {
    color: var(--gray-600);
    font-weight: 500;
    font-size: 0.9rem;
    position: relative;
}

.nav-links a::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--gradient);
    transition: width 0.3s ease;
}

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

.nav-links a:hover::after {
    width: 100%;
}

.mobile-menu-btn {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 5px;
}

.mobile-menu-btn span {
    width: 24px;
    height: 2px;
    background: var(--gray-700);
    transition: all 0.3s ease;
}

/* ============================================
   Hero Section
   ============================================ */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 8rem 2rem 4rem;
    max-width: 1280px;
    margin: 0 auto;
    gap: 4rem;
    position: relative;
}

.hero-content {
    flex: 1;
    max-width: 600px;
}

.hero-badge {
    display: inline-block;
    padding: 0.5rem 1rem;
    background: var(--primary-light);
    color: var(--primary-dark);
    border-radius: var(--radius-full);
    font-size: 0.875rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
}

.hero h1 {
    margin-bottom: 1.5rem;
}

.gradient-text {
    background: var(--gradient-text);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 1.125rem;
    color: var(--gray-600);
    margin-bottom: 2rem;
    line-height: 1.8;
}

.hero-cta {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.875rem 1.75rem;
    border-radius: var(--radius-md);
    font-weight: 600;
    font-size: 0.9rem;
    transition: all 0.3s ease;
    cursor: pointer;
    border: none;
}

.btn-primary {
    background: var(--gradient);
    color: var(--white);
    box-shadow: var(--shadow-md);
}

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

.btn-secondary {
    background: var(--white);
    color: var(--gray-700);
    border: 2px solid var(--gray-200);
}

.btn-secondary:hover {
    border-color: var(--primary);
    color: var(--primary);
}

.hero-visual {
    flex: 1;
    position: relative;
    height: 400px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.floating-card {
    position: absolute;
    background: var(--white);
    padding: 1rem 1.5rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-weight: 500;
    font-size: 0.9rem;
    animation: float 6s ease-in-out infinite;
}

.floating-card .card-icon {
    font-size: 1.5rem;
}

.card-1 {
    top: 20%;
    left: 10%;
    animation-delay: 0s;
}

.card-2 {
    top: 50%;
    right: 10%;
    animation-delay: 2s;
}

.card-3 {
    bottom: 20%;
    left: 20%;
    animation-delay: 4s;
}

@keyframes float {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-20px); }
}

/* ============================================
   Section Common Styles
   ============================================ */
section {
    padding: 6rem 2rem;
    max-width: 1280px;
    margin: 0 auto;
}

.section-header {
    text-align: center;
    margin-bottom: 4rem;
}

.section-badge {
    display: inline-block;
    padding: 0.375rem 1rem;
    background: var(--primary-light);
    color: var(--primary-dark);
    border-radius: var(--radius-full);
    font-size: 0.8rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 1rem;
}

.section-header h2 {
    margin-bottom: 0.5rem;
}

/* ============================================
   About Section
   ============================================ */
.about-grid {
    display: grid;
    grid-template-columns: 1.5fr 1fr;
    gap: 4rem;
    align-items: start;
}

.about-lead {
    font-size: 1.25rem;
    color: var(--gray-700);
    margin-bottom: 2rem;
    line-height: 1.8;
}

.about-highlights {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.highlight-item {
    display: flex;
    gap: 1rem;
    padding: 1.25rem;
    background: var(--white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    transition: all 0.3s ease;
}

.highlight-item:hover {
    transform: translateX(8px);
    box-shadow: var(--shadow-md);
}

.highlight-icon {
    font-size: 2rem;
    flex-shrink: 0;
}

.highlight-text h4 {
    margin-bottom: 0.25rem;
    color: var(--gray-900);
}

.highlight-text p {
    font-size: 0.9rem;
    color: var(--gray-600);
}

.about-stats {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1.5rem;
}

.stat-card {
    background: var(--white);
    padding: 1.5rem;
    border-radius: var(--radius-lg);
    text-align: center;
    box-shadow: var(--shadow);
    transition: all 0.3s ease;
}

.stat-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.stat-number {
    font-size: 2.5rem;
    font-weight: 800;
    background: var(--gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.stat-label {
    font-weight: 600;
    color: var(--gray-800);
    margin-bottom: 0.25rem;
}

.stat-desc {
    font-size: 0.8rem;
    color: var(--gray-500);
}

/* ============================================
   Experience Section
   ============================================ */
.experience {
    background: linear-gradient(180deg, var(--gray-50) 0%, var(--white) 100%);
}

.timeline {
    position: relative;
    padding-left: 2rem;
}

.timeline::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 2px;
    background: var(--gradient);
}

.timeline-item {
    position: relative;
    padding-bottom: 3rem;
}

.timeline-item:last-child {
    padding-bottom: 0;
}

.timeline-marker {
    position: absolute;
    left: -2rem;
    top: 0;
    width: 12px;
    height: 12px;
    background: var(--primary);
    border-radius: 50%;
    transform: translateX(-5px);
    box-shadow: 0 0 0 4px var(--primary-light);
}

.timeline-content {
    background: var(--white);
    padding: 2rem;
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow);
    margin-left: 1rem;
    transition: all 0.3s ease;
}

.timeline-content:hover {
    box-shadow: var(--shadow-lg);
}

.timeline-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 0.5rem;
    flex-wrap: wrap;
    gap: 1rem;
}

.company-info h3 {
    color: var(--gray-900);
    margin-bottom: 0.25rem;
}

.location {
    font-size: 0.875rem;
    color: var(--gray-500);
}

.timeline-date {
    font-size: 0.875rem;
    color: var(--primary);
    font-weight: 600;
    background: var(--primary-light);
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-full);
}

.role {
    font-weight: 600;
    color: var(--gray-700);
    margin-bottom: 1rem;
    font-size: 1.1rem;
}

.achievements {
    list-style: none;
    margin-bottom: 1.5rem;
}

.achievements li {
    position: relative;
    padding-left: 1.5rem;
    margin-bottom: 0.75rem;
    color: var(--gray-600);
    font-size: 0.95rem;
}

.achievements li::before {
    content: '▸';
    position: absolute;
    left: 0;
    color: var(--primary);
    font-weight: bold;
}

.tech-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.tech-tags span {
    padding: 0.375rem 0.875rem;
    background: var(--gray-100);
    color: var(--gray-700);
    border-radius: var(--radius-full);
    font-size: 0.8rem;
    font-weight: 500;
}

/* ============================================
   Education Section
   ============================================ */
.education-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.education-card {
    background: var(--white);
    border-radius: var(--radius-xl);
    padding: 2rem;
    box-shadow: var(--shadow);
    display: flex;
    gap: 1.5rem;
    transition: all 0.3s ease;
}

.education-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.education-card.featured {
    background: var(--gradient);
    color: var(--white);
    grid-column: span 2;
}

.education-card.featured h3,
.education-card.featured p {
    color: var(--white);
}

.education-card.featured .edu-location {
    opacity: 0.9;
}

.edu-icon {
    font-size: 3rem;
    flex-shrink: 0;
}

.edu-content h3 {
    margin-bottom: 0.5rem;
}

.edu-location {
    font-size: 0.9rem;
    color: var(--gray-500);
    margin-bottom: 0.5rem;
}

.edu-degree {
    color: var(--gray-700);
    margin-bottom: 0.25rem;
}

.edu-date {
    font-size: 0.875rem;
    color: var(--gray-500);
    margin-bottom: 1rem;
}

.edu-highlight {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-top: 1rem;
}

.highlight-badge {
    padding: 0.375rem 0.875rem;
    background: rgba(255, 255, 255, 0.2);
    border-radius: var(--radius-full);
    font-size: 0.8rem;
    font-weight: 600;
}

.edu-project {
    font-size: 0.9rem;
    color: var(--gray-600);
    padding: 1rem;
    background: var(--gray-50);
    border-radius: var(--radius);
    margin-top: 1rem;
}

/* ============================================
   Awards Section
   ============================================ */
.awards {
    background: linear-gradient(180deg, var(--white) 0%, var(--gray-50) 100%);
}

.awards-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1.5rem;
}

.award-card {
    background: var(--white);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    display: flex;
    gap: 1rem;
    box-shadow: var(--shadow);
    transition: all 0.3s ease;
    border-left: 4px solid var(--gray-300);
}

.award-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.award-card.gold {
    border-left-color: var(--gold);
    background: linear-gradient(135deg, var(--white) 0%, #fffbeb 100%);
}

.award-icon {
    font-size: 2rem;
    flex-shrink: 0;
}

.award-content h4 {
    margin-bottom: 0.25rem;
    color: var(--gray-900);
}

.award-content p {
    font-size: 0.9rem;
    color: var(--gray-600);
    margin-bottom: 0.5rem;
}

.award-year {
    font-size: 0.8rem;
    color: var(--primary);
    font-weight: 600;
}

/* ============================================
   Skills Section
   ============================================ */
.skills-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2rem;
}

.skill-category {
    background: var(--white);
    border-radius: var(--radius-xl);
    padding: 2rem;
    box-shadow: var(--shadow);
}

.category-header {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-bottom: 1.5rem;
}

.category-icon {
    font-size: 1.5rem;
}

.category-header h3 {
    font-size: 1.1rem;
}

.skill-items {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.skill-item {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.skill-name {
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--gray-700);
}

.skill-bar {
    height: 8px;
    background: var(--gray-200);
    border-radius: var(--radius-full);
    overflow: hidden;
}

.skill-progress {
    height: 100%;
    background: var(--gradient);
    border-radius: var(--radius-full);
    transition: width 1s ease;
}

.language-badges {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-top: 1rem;
}

.lang-badge {
    padding: 0.375rem 0.75rem;
    background: var(--primary-light);
    color: var(--primary-dark);
    border-radius: var(--radius-full);
    font-size: 0.8rem;
    font-weight: 600;
}

/* ============================================
   Contact Section
   ============================================ */
.contact {
    background: var(--dark);
    color: var(--white);
    border-radius: var(--radius-xl) var(--radius-xl) 0 0;
    margin-top: 4rem;
}

.contact .section-badge {
    background: rgba(255, 255, 255, 0.1);
    color: var(--white);
}

.contact .section-header h2 {
    color: var(--white);
}

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

.contact-intro {
    font-size: 1.1rem;
    color: var(--gray-300);
    max-width: 600px;
    margin: 0 auto 3rem;
}

.contact-cards {
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: 1.5rem;
}

.contact-card {
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid rgba(255, 255, 255, 0.1);
    border-radius: var(--radius-lg);
    padding: 2rem;
    min-width: 200px;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.75rem;
    transition: all 0.3s ease;
}

.contact-card:hover {
    background: rgba(255, 255, 255, 0.1);
    transform: translateY(-4px);
}

.contact-icon {
    font-size: 2rem;
}

.contact-label {
    font-size: 0.8rem;
    color: var(--gray-400);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.contact-value {
    font-weight: 600;
    color: var(--white);
}

/* ============================================
   Footer
   ============================================ */
footer {
    background: var(--gray-900);
    color: var(--white);
    padding: 3rem 2rem 1.5rem;
}

.footer-content {
    max-width: 1280px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-bottom: 2rem;
    border-bottom: 1px solid var(--gray-800);
    flex-wrap: wrap;
    gap: 2rem;
}

.footer-logo {
    font-size: 1.25rem;
    font-weight: 700;
}

.footer-brand p {
    color: var(--gray-500);
    font-size: 0.9rem;
    margin-top: 0.5rem;
}

.footer-links {
    display: flex;
    gap: 2rem;
}

.footer-links a {
    color: var(--gray-400);
    font-size: 0.9rem;
}

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

.footer-bottom {
    max-width: 1280px;
    margin: 0 auto;
    padding-top: 1.5rem;
    text-align: center;
}

.footer-bottom p {
    color: var(--gray-500);
    font-size: 0.85rem;
}

/* ============================================
   Responsive Design
   ============================================ */
@media (max-width: 1024px) {
    .hero {
        flex-direction: column;
        text-align: center;
        padding-top: 7rem;
    }

    .hero-content {
        max-width: 100%;
    }

    .hero-cta {
        justify-content: center;
    }

    .hero-visual {
        width: 100%;
        height: 300px;
    }

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

    .about-stats {
        grid-template-columns: repeat(4, 1fr);
    }

    .education-card.featured {
        grid-column: span 1;
    }
}

@media (max-width: 768px) {
    .nav-links {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: var(--white);
        flex-direction: column;
        padding: 1rem;
        gap: 0;
        box-shadow: var(--shadow-lg);
    }

    .nav-links.active {
        display: flex;
    }

    .nav-links li {
        padding: 0.75rem 1rem;
        border-bottom: 1px solid var(--gray-100);
    }

    .mobile-menu-btn {
        display: flex;
    }

    .hero-visual {
        display: none;
    }

    .about-stats {
        grid-template-columns: repeat(2, 1fr);
    }

    .timeline {
        padding-left: 1.5rem;
    }

    .timeline-content {
        padding: 1.5rem;
        margin-left: 0.5rem;
    }

    .footer-content {
        flex-direction: column;
        text-align: center;
    }

    .footer-links {
        flex-wrap: wrap;
        justify-content: center;
    }
}

@media (max-width: 480px) {
    section {
        padding: 4rem 1rem;
    }

    .hero h1 {
        font-size: 1.75rem;
    }

    .about-stats {
        grid-template-columns: 1fr;
    }

    .stat-card {
        display: flex;
        align-items: center;
        gap: 1rem;
        text-align: left;
    }

    .stat-number {
        font-size: 2rem;
    }

    .contact-cards {
        flex-direction: column;
    }

    .contact-card {
        width: 100%;
    }
}

/* ============================================
   Animations
   ============================================ */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.hero-content,
.timeline-item,
.education-card,
.award-card,
.skill-category {
    animation: fadeInUp 0.6s ease forwards;
}

.timeline-item:nth-child(2) { animation-delay: 0.2s; }
.timeline-item:nth-child(3) { animation-delay: 0.4s; }

/* Hover animations */
.btn,
.stat-card,
.highlight-item,
.education-card,
.award-card,
.contact-card {
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

/* Smooth scroll padding for fixed header */
:target {
    scroll-margin-top: 80px;
}