* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f9fafb;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header & Navigation */
.header {
    background: #ffffff;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    position: sticky;
    top: 0;
    z-index: 100;
}

.nav {
    display: flex;
    justify-content: space-between;
    align-content: center;
    padding: 1rem 0;
}

.logo {
    font-size: 1.5rem;
    font-weight: bold;
    color: #0070f3
}

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

.nav-menu a {
    text-decoration: none;
    color: #333;
    font-weight: 500;
    transition: color 0.3s ease;
}

.nav-menu a:hover {
    color: #0070f3;
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, #667eee 0%, #764ba2 100%);
    color: white;
    text-align: center;
    padding: 6rem 0;
}

.hero h1 {
    font-size: 3rem;
    margin-bottom: 0.5rem;
}

.hero h2 {
    font-size: 2rem;
    margin-bottom: 1rem;
    opacity: 0.9;
}

.hero p {
    font-size: 1.25rem;
    opacity: 0.8;
}

/* Sections */
.section {
    padding: 4rem 0;
}

.section h2 {
    font-size: 2.5rem;
    text-align: center;
    margin-bottom: 3rem;
    color: #1f2937;
}

/* Skills Grid */
.skills-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
}

.skill-card {
    background: white;
    border: 1px solid #e5e7eb;
    border-radius: 12px;
    padding: 2rem;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.05);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.skill-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.1);
}

.skill-card h3 {
    margin-bottom: 1rem;
    color: #0070f3;
}

.skill-card ul {
    list-style: none;
}

.skill-card li {
    padding: 0.25rem 0;
    color: #6b7280;
}

/* Projects Grid */
.projects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.project-card {
    background: white;
    border: 1px solid #e5e7eb;
    border-radius: 12px;
    padding: 1.5rem;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.05);
    transition: all 0.3s ease;
}

.project-card:hover {
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.1);
}

.project-card h3 {
    margin-bottom: 0.5rem;
    color: #1f2937;
}

.project-card p {
    color: #6b7280;
    margin-bottom: 1rem;
}

.project-card a {
    color: #0070f3;
    text-decoration: none;
    font-weight: 500;
}

.project-card a:hover {
    text-decoration: underline;
}

/* Footer */
.footer {
    background: #1f2937;
    color: white;
    padding: 3rem 0;
    text-align: center;
    margin-top: 4rem;
}

.footer p {
    margin-top: 1rem;
}

.social-links {
    display: flex;
    justify-content: center;
    gap: 2rem
}

.social-links a {
    color: white;
    text-decoration: none;
    transition: opacity 0.3s ease;
}

.social-links a:hover {
    opacity: 0.7;
}

/* Responsive Design (기본) */
@media (max-width: 768px) {
    .nav {
        flex-direction: column;
        gap: 1rem
    }

    .nav-menu {
        gap: 1rem
    }

    .hero {
        padding: 3rem 0;
    }

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

    .hero h2 {
        font-size: 1.5rem;
    }

    .section h2 {
        font-size: 2rem;
    }

    .skills-grid,
    .projetcts-grid {
        grid-template-columns: 1fr;
    }
}