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

:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --bg-primary: #ffffff;
    --bg-secondary: #f9fafb;
    --bg-dark: #111827;
    --border-color: #e5e7eb;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --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);
    --transition: all 0.3s ease;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', 'Noto Sans KR', -apple-system, BlinkMacSystemFont, sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-primary);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
}

/* Navigation */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
    z-index: 1000;
}

.nav-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 72px;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-primary);
    text-decoration: none;
    letter-spacing: -0.02em;
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 32px;
}

.nav-links a {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
}

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

.lang-toggle {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    padding: 8px 16px;
    border-radius: 6px;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    font-family: inherit;
}

.lang-toggle:hover {
    background: var(--border-color);
}

.mobile-menu-btn {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
}

.mobile-menu-btn span {
    display: block;
    width: 24px;
    height: 2px;
    background: var(--text-primary);
    transition: var(--transition);
}

.mobile-menu {
    display: none;
    position: fixed;
    top: 72px;
    left: 0;
    right: 0;
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    flex-direction: column;
    padding: 16px 24px;
    gap: 16px;
    z-index: 999;
}

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

.mobile-menu a {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    padding: 8px 0;
}

/* Hero Section */
.hero {
    padding: 160px 0 100px;
    text-align: center;
    background: linear-gradient(180deg, var(--bg-secondary) 0%, var(--bg-primary) 100%);
}

.hero h1 {
    font-size: clamp(2.5rem, 5vw, 4rem);
    font-weight: 700;
    line-height: 1.1;
    letter-spacing: -0.02em;
    margin-bottom: 24px;
    color: var(--text-primary);
}

.hero-subtitle {
    font-size: 1.25rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto 40px;
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 14px 28px;
    border-radius: 8px;
    font-weight: 600;
    text-decoration: none;
    transition: var(--transition);
    border: none;
    cursor: pointer;
    font-size: 1rem;
    font-family: inherit;
}

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

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

/* Services Section */
.services {
    padding: 100px 0;
}

.services h2, .about h2, .contact h2 {
    font-size: 2.5rem;
    font-weight: 700;
    text-align: center;
    margin-bottom: 60px;
    letter-spacing: -0.02em;
}

.services-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 32px;
}

.service-card {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    padding: 40px 32px;
    transition: var(--transition);
}

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

.service-icon {
    color: var(--primary-color);
    margin-bottom: 24px;
}

.service-card h3 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: 16px;
}

.service-card p {
    color: var(--text-secondary);
    line-height: 1.7;
}

/* About Section */
.about {
    padding: 100px 0;
    background: var(--bg-secondary);
}

.about-content {
    max-width: 800px;
    margin: 0 auto;
    text-align: center;
}

.about-content > p {
    font-size: 1.125rem;
    color: var(--text-secondary);
    line-height: 1.8;
    margin-bottom: 48px;
}

.tech-stack h3 {
    font-size: 1.25rem;
    margin-bottom: 20px;
}

.tech-tags {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 12px;
}

.tech-tags span {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    padding: 8px 16px;
    border-radius: 20px;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
}

/* Contact Section */
.contact {
    padding: 100px 0;
}

.contact-intro {
    text-align: center;
    font-size: 1.125rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: -40px auto 48px;
}

.contact-form {
    max-width: 600px;
    margin: 0 auto;
}

.form-group {
    margin-bottom: 24px;
}

.form-group label {
    display: block;
    font-weight: 500;
    margin-bottom: 8px;
    color: var(--text-primary);
}

.form-group input,
.form-group textarea {
    width: 100%;
    padding: 14px 16px;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    font-family: inherit;
    transition: var(--transition);
    background: var(--bg-primary);
}

.form-group input:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.form-group textarea {
    resize: vertical;
    min-height: 120px;
}

.contact-form .btn {
    width: 100%;
}

/* Footer */
.footer {
    background: var(--bg-dark);
    color: rgba(255, 255, 255, 0.7);
    padding: 32px 0;
    text-align: center;
}

/* Responsive */
@media (max-width: 768px) {
    .nav-links {
        display: none;
    }

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

    .hero {
        padding: 120px 0 80px;
    }

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

    .hero-subtitle {
        font-size: 1rem;
    }

    .services, .about, .contact {
        padding: 60px 0;
    }

    .services h2, .about h2, .contact h2 {
        font-size: 2rem;
        margin-bottom: 40px;
    }

    .service-card {
        padding: 32px 24px;
    }

    .contact-intro {
        margin: -20px auto 32px;
    }
}

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

.hero h1, .hero-subtitle, .hero .btn {
    animation: fadeInUp 0.6s ease forwards;
}

.hero-subtitle {
    animation-delay: 0.1s;
}

.hero .btn {
    animation-delay: 0.2s;
}