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

:root {
    --primary-color: #1a1a1a;
    --secondary-color: #0066cc;
    --accent-color: #f0f0f0;
    --text-color: #333;
    --light-text: #666;
    --border-color: #e0e0e0;
    --white: #ffffff;
    --transition: all 0.3s ease;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    color: var(--text-color);
    background-color: var(--white);
    line-height: 1.6;
}

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

/* 헤더 & 네비게이션 */
.header {
    position: fixed;
    top: 0;
    width: 100%;
    background-color: var(--white);
    border-bottom: 1px solid var(--border-color);
    z-index: 1000;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.05);
}

.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2rem;
    max-width: 1200px;
    margin: 0 auto;
    width: 100%;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
    text-decoration: none;
    letter-spacing: -0.5px;
}

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

.nav-link {
    text-decoration: none;
    color: var(--text-color);
    font-weight: 500;
    transition: var(--transition);
    position: relative;
}

.nav-link:hover,
.nav-link.active {
    color: var(--secondary-color);
}

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 100%;
    height: 2px;
    background-color: var(--secondary-color);
}

.nav-toggle {
    display: none;
    flex-direction: column;
    cursor: pointer;
}

.nav-toggle span {
    width: 25px;
    height: 3px;
    background-color: var(--text-color);
    margin: 5px 0;
    transition: var(--transition);
}

.nav-toggle.active span:nth-child(1) {
    transform: rotate(45deg) translate(10px, 10px);
}

.nav-toggle.active span:nth-child(2) {
    opacity: 0;
}

.nav-toggle.active span:nth-child(3) {
    transform: rotate(-45deg) translate(7px, -7px);
}

/* 버튼 */
.btn {
    display: inline-block;
    padding: 12px 32px;
    border-radius: 4px;
    text-decoration: none;
    font-weight: 600;
    transition: var(--transition);
    border: none;
    cursor: pointer;
    font-size: 1rem;
}

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

.btn-primary:hover {
    background-color: #0052a3;
    transform: translateY(-2px);
}

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

.btn-secondary:hover {
    background-color: var(--secondary-color);
    color: var(--white);
    transform: translateY(-2px);
}

/* 섹션 타이틀 */
.section-title {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 3rem;
    text-align: center;
    color: var(--primary-color);
    position: relative;
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: -15px;
    left: 50%;
    transform: translateX(-50%);
    width: 60px;
    height: 4px;
    background-color: var(--secondary-color);
    border-radius: 2px;
}

/* 소개 섹션 (Hero) */
.hero {
    margin-top: 80px;
    padding: 100px 0;
    background: linear-gradient(135deg, #f5f5f5 0%, var(--white) 100%);
    min-height: calc(100vh - 80px);
    display: flex;
    align-items: center;
    justify-content: center;
}

.hero-content {
    text-align: center;
    animation: fadeInUp 1s ease;
}

.hero-title {
    font-size: 3.5rem;
    font-weight: 800;
    margin-bottom: 1rem;
    color: var(--primary-color);
    line-height: 1.2;
}

.hero-subtitle {
    font-size: 1.5rem;
    color: var(--secondary-color);
    margin-bottom: 1rem;
    font-weight: 600;
}

.hero-description {
    font-size: 1.1rem;
    color: var(--light-text);
    max-width: 600px;
    margin: 0 auto 2rem;
    line-height: 1.8;
}

.hero-buttons {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
}

/* 프로젝트 섹션 */
.projects {
    padding: 80px 0;
    background-color: var(--white);
}

.projects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
    gap: 2rem;
}

.project-card {
    background-color: var(--white);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    overflow: hidden;
    transition: var(--transition);
    opacity: 0;
    animation: fadeInUp 0.6s ease forwards;
}

.project-card:nth-child(1) { animation-delay: 0.1s; }
.project-card:nth-child(2) { animation-delay: 0.2s; }
.project-card:nth-child(3) { animation-delay: 0.3s; }
.project-card:nth-child(4) { animation-delay: 0.4s; }
.project-card:nth-child(5) { animation-delay: 0.5s; }
.project-card:nth-child(6) { animation-delay: 0.6s; }

.project-card:hover {
    border-color: var(--secondary-color);
    box-shadow: 0 10px 30px rgba(0, 102, 204, 0.1);
    transform: translateY(-5px);
}

.project-image {
    width: 100%;
    height: 200px;
    background-color: var(--accent-color);
    display: flex;
    align-items: center;
    justify-content: center;
    overflow: hidden;
}

.placeholder-image {
    font-size: 1.2rem;
    color: var(--light-text);
    background: linear-gradient(135deg, #e0e0e0 0%, #f0f0f0 100%);
    width: 100%;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
}

.project-card:hover .placeholder-image {
    background: linear-gradient(135deg, #0066cc 0%, #0052a3 100%);
    color: var(--white);
}

.project-card h3 {
    font-size: 1.3rem;
    margin: 1.5rem 1.5rem 0.5rem;
    color: var(--primary-color);
}

.project-card p {
    color: var(--light-text);
    margin: 0 1.5rem;
    font-size: 0.95rem;
    line-height: 1.6;
}

.project-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin: 1rem 1.5rem;
}

.tag {
    display: inline-block;
    background-color: var(--accent-color);
    color: var(--text-color);
    padding: 0.3rem 0.8rem;
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 500;
}

.project-link {
    display: inline-block;
    color: var(--secondary-color);
    text-decoration: none;
    margin: 1rem 1.5rem 1.5rem;
    font-weight: 600;
    transition: var(--transition);
}

.project-link:hover {
    color: #0052a3;
    transform: translateX(5px);
}

/* 기술 스택 섹션 */
.skills {
    padding: 80px 0;
    background-color: var(--accent-color);
}

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

.skill-category {
    background-color: var(--white);
    padding: 2rem;
    border-radius: 8px;
    border-left: 4px solid var(--secondary-color);
    opacity: 0;
    animation: fadeInUp 0.6s ease forwards;
}

.skill-category:nth-child(1) { animation-delay: 0.1s; }
.skill-category:nth-child(2) { animation-delay: 0.2s; }
.skill-category:nth-child(3) { animation-delay: 0.3s; }

.skill-category h3 {
    font-size: 1.3rem;
    margin-bottom: 1.5rem;
    color: var(--primary-color);
}

.skill-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.7rem;
}

.skill-badge {
    display: inline-block;
    background-color: var(--secondary-color);
    color: var(--white);
    padding: 0.5rem 1rem;
    border-radius: 20px;
    font-size: 0.9rem;
    font-weight: 500;
    transition: var(--transition);
}

.skill-badge:hover {
    background-color: #0052a3;
    transform: scale(1.05);
}

/* 경력사항 섹션 */
.experience {
    padding: 80px 0;
    background-color: var(--white);
}

.experience-timeline {
    position: relative;
    max-width: 800px;
    margin: 0 auto;
}

.experience-timeline::before {
    content: '';
    position: absolute;
    left: 30px;
    top: 0;
    bottom: 0;
    width: 2px;
    background-color: var(--secondary-color);
}

.timeline-item {
    position: relative;
    margin-bottom: 3rem;
    margin-left: 100px;
    opacity: 0;
    animation: fadeInUp 0.6s ease forwards;
}

.timeline-item:nth-child(1) { animation-delay: 0.1s; }
.timeline-item:nth-child(2) { animation-delay: 0.2s; }
.timeline-item:nth-child(3) { animation-delay: 0.3s; }

.timeline-marker {
    position: absolute;
    left: -75px;
    top: 0;
    width: 20px;
    height: 20px;
    background-color: var(--secondary-color);
    border: 4px solid var(--white);
    border-radius: 50%;
    box-shadow: 0 0 0 4px var(--accent-color);
}

.timeline-content {
    background-color: var(--accent-color);
    padding: 2rem;
    border-radius: 8px;
    border-left: 3px solid var(--secondary-color);
}

.timeline-content h3 {
    font-size: 1.3rem;
    color: var(--primary-color);
    margin-bottom: 0.3rem;
}

.company {
    color: var(--secondary-color);
    font-weight: 600;
    margin-bottom: 0.3rem;
}

.period {
    color: var(--light-text);
    font-size: 0.9rem;
    margin-bottom: 1rem;
}

.description {
    color: var(--text-color);
    line-height: 1.6;
}

/* 연락처 섹션 */
.contact {
    padding: 80px 0;
    background: linear-gradient(135deg, #f5f5f5 0%, var(--white) 100%);
}

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

.contact-text {
    font-size: 1.3rem;
    color: var(--text-color);
    margin-bottom: 2rem;
}

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

.contact-link {
    display: flex;
    align-items: center;
    gap: 0.7rem;
    padding: 12px 24px;
    background-color: var(--white);
    border: 2px solid var(--border-color);
    border-radius: 8px;
    color: var(--text-color);
    text-decoration: none;
    font-weight: 600;
    transition: var(--transition);
}

.contact-link:hover {
    border-color: var(--secondary-color);
    color: var(--secondary-color);
    background-color: var(--accent-color);
    transform: translateY(-3px);
}

.contact-link i {
    font-size: 1.2rem;
}

/* 제안하기 섹션 */
.proposal {
    padding: 80px 0;
    background-color: var(--white);
}

.proposal-form {
    max-width: 600px;
    margin: 0 auto;
    background-color: var(--accent-color);
    padding: 2.5rem;
    border-radius: 8px;
    border: 1px solid var(--border-color);
}

.form-group {
    margin-bottom: 1.5rem;
    display: flex;
    flex-direction: column;
}

.form-group label {
    margin-bottom: 0.5rem;
    font-weight: 600;
    color: var(--primary-color);
}

.form-group input,
.form-group textarea {
    padding: 12px;
    border: 1px solid var(--border-color);
    border-radius: 4px;
    font-family: inherit;
    font-size: 1rem;
    color: var(--text-color);
    transition: var(--transition);
}

.form-group input:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--secondary-color);
    background-color: var(--white);
    box-shadow: 0 0 0 3px rgba(0, 102, 204, 0.1);
}

.form-group button {
    margin-top: 1rem;
}

.form-message {
    text-align: center;
    margin-top: 1rem;
    padding: 1rem;
    border-radius: 4px;
    display: none;
}

.form-message.success {
    display: block;
    background-color: #d4edda;
    color: #155724;
    border: 1px solid #c3e6cb;
}

.form-message.error {
    display: block;
    background-color: #f8d7da;
    color: #721c24;
    border: 1px solid #f5c6cb;
}

/* 푸터 */
.footer {
    background-color: var(--primary-color);
    color: var(--white);
    text-align: center;
    padding: 2rem;
    border-top: 1px solid var(--border-color);
}

/* 애니메이션 */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* 반응형 디자인 */
@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        left: -100%;
        top: 70px;
        flex-direction: column;
        background-color: var(--white);
        width: 100%;
        text-align: center;
        transition: 0.3s;
        box-shadow: 0 10px 27px rgba(0, 0, 0, 0.05);
        gap: 0;
        padding: 2rem 0;
    }

    .nav-menu.active {
        left: 0;
    }

    .nav-link {
        display: block;
        padding: 1.5rem;
        width: 100%;
        transition: var(--transition);
    }

    .nav-link:hover {
        background-color: var(--accent-color);
    }

    .nav-link.active::after {
        display: none;
    }

    .nav-toggle {
        display: flex;
    }

    .hero-title {
        font-size: 2.5rem;
    }

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

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

    .section-title::after {
        width: 40px;
    }

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

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

    .experience-timeline::before {
        left: 15px;
    }

    .timeline-marker {
        left: -40px;
        width: 16px;
        height: 16px;
    }

    .timeline-item {
        margin-left: 50px;
    }

    .contact-links {
        gap: 1rem;
    }

    .contact-link {
        padding: 10px 16px;
        font-size: 0.9rem;
    }

    .proposal-form {
        padding: 1.5rem;
    }

    .hero-buttons {
        flex-direction: column;
    }

    .btn {
        width: 100%;
        text-align: center;
    }
}

@media (max-width: 480px) {
    .navbar {
        padding: 0.8rem 1rem;
    }

    .logo {
        font-size: 1.2rem;
    }

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

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

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

    .section-title {
        font-size: 1.5rem;
        margin-bottom: 2rem;
    }

    .projects-grid {
        gap: 1.5rem;
    }

    .project-card h3 {
        font-size: 1.1rem;
    }

    .contact-links {
        flex-direction: column;
        align-items: stretch;
    }

    .contact-link {
        width: 100%;
        justify-content: center;
    }
}