/* ==========================================================================
   1. 전역 스타일 및 초기화
   ========================================================================== */
* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, system-ui, Roboto, sans-serif;
}

body {
    background-color: #f1f5f9; /* 편안한 연회색 배경 */
    color: #334155;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* ==========================================================================
   2. 네비게이션 바 (제공해주신 사진 디자인 반영)
   ========================================================================== */
.navbar {
    background-color: #1e3a8a; /* 사진 속 그 깊고 진한 블루 색상 */
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

.nav-container {
    max-width: 900px;
    margin: 0 auto;
    display: flex;
    justify-content: space-around; /* 메뉴 간격을 일정하게 배치 */
    align-items: center;
    padding: 0 10px;
}

.nav-item {
    color: #ffffff;
    text-decoration: none;
    font-size: 1.1rem;
    font-weight: 700;
    padding: 18px 20px;
    cursor: pointer;
    transition: all 0.2s ease;
    border-bottom: 4px solid transparent; /* 하단 바 효과용 공간 확보 */
    text-align: center;
    flex: 1;
}

/* 메뉴 마우스 오버 및 활성화(Active) 상태 스타일 */
.nav-item:hover, .nav-item.active {
    background-color: rgba(255, 255, 255, 0.1);
    border-bottom: 4px solid #3b82f6; /* 활성화 시 푸른빛 하단 바 채우기 */
    color: #93c5fd; /* 텍스트 색상도 부드럽게 변경 */
}

/* ==========================================================================
   3. 메인 콘텐츠 레이아웃
   ========================================================================== */
.main-content {
    flex: 1;
    max-width: 850px;
    width: 100%;
    margin: 40px auto;
    padding: 0 20px;
}

/* 공통 카드 스타일 */
.content-card {
    background: #ffffff;
    border-radius: 20px;
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.05);
    padding: 40px;
}

/* ==========================================================================
   4. HOME 스타일
   ========================================================================== */
.home-banner {
    text-align: center;
    padding: 60px 20px;
}
.home-banner h1 {
    font-size: 2.5rem;
    color: #1e293b;
    margin-bottom: 15px;
    font-weight: 800;
}
.home-banner p {
    font-size: 1.2rem;
    color: #64748b;
    line-height: 1.6;
}

/* ==========================================================================
   5. 자기소개 스타일
   ========================================================================== */
.profile-card {
    border-top: 8px solid #2563eb;
}
.profile-header {
    text-align: center;
    margin-bottom: 35px;
}
.profile-img-container {
    display: inline-block;
    margin-bottom: 12px;
}
.profile-img {
    width: 180px;
    height: 180px;
    object-fit: cover;
    border-radius: 50%;
    border: 4px solid #f8fafc;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    transition: transform 0.3s ease;
}
.profile-img:hover { transform: scale(1.05); }
.img-caption {
    font-size: 0.85rem;
    color: #64748b;
    margin-top: 10px;
    display: block;
}
.profile-header h1 {
    font-size: 1.8rem;
    color: #1e293b;
    font-weight: 800;
}
.profile-card h2 {
    font-size: 1.25rem;
    color: #1e3a8a;
    border-left: 4px solid #2563eb;
    padding-left: 10px;
    margin-bottom: 15px;
    font-weight: 700;
    margin-top: 30px;
}
.profile-card h2:first-of-type { margin-top: 0; }
.intro-text p {
    font-size: 0.98rem;
    line-height: 1.7;
    color: #475569;
    margin-bottom: 8px;
}
.info-table {
    width: 100%;
    border-collapse: collapse;
    background-color: #f8fafc;
    border-radius: 12px;
    overflow: hidden;
}
.info-table th, .info-table td {
    padding: 14px 18px;
    text-align: left;
    font-size: 0.95rem;
}
.info-table th {
    background-color: #eff6ff;
    color: #1e40af;
    font-weight: 700;
    width: 30%;
    border-right: 1px solid #e2e8f0;
}
.info-table tr:not(:last-child) { border-bottom: 1px solid #e2e8f0; }
.skills-container { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 10px; }
.skill-badge {
    background-color: #f1f5f9;
    color: #475569;
    padding: 8px 16px;
    border-radius: 20px;
    font-size: 0.9rem;
    font-weight: 600;
}
.deeds-list { list-style: none; display: flex; flex-direction: column; gap: 10px; margin-top: 10px; }
.deeds-list li { position: relative; padding-left: 24px; font-size: 0.95rem; color: #475569; }
.deeds-list li::before { content: "🌱"; position: absolute; left: 0; top: 0px; }

/* ==========================================================================
   6. 작품 & JS (문제집 추천) 스타일
   ========================================================================== */
.project-header {
    margin-bottom: 30px;
    text-align: center;
}
.project-header h2 {
    font-size: 2rem;
    color: #1e293b;
    margin-bottom: 8px;
    font-weight: 800;
}
.subject-title {
    font-size: 1.4rem;
    color: #1e3a8a;
    margin-bottom: 15px;
    font-weight: 700;
}
.category-card {
    background-color: #ffffff;
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
    border-left: 6px solid #1a4f9c;
    margin-bottom: 16px;
    overflow: hidden;
    transition: all 0.3s ease;
}
.category-card[open] { box-shadow: 0 8px 20px rgba(0, 0, 0, 0.1); }
.card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px 24px;
    font-size: 1.15rem;
    font-weight: 700;
    color: #1e293b;
    cursor: pointer;
    list-style: none;
}
.card-header::-webkit-details-marker { display: none; }
.card-header::after { content: '▼'; font-size: 0.8rem; color: #94a3b8; transition: transform 0.3s ease; }
.category-card[open] .card-header::after { transform: rotate(180deg); color: #1a4f9c; }
.card-content { padding: 10px 24px 24px 24px; border-top: 1px solid #f1f5f9; background-color: #fcfdfe; }
.books-grid { display: flex; flex-direction: column; gap: 24px; }
.book-item { display: flex; gap: 20px; align-items: flex-start; padding-bottom: 24px; border-bottom: 1px dashed #e2e8f0; }
.book-item:last-child { padding-bottom: 0; border-bottom: none; }
.book-img-link { flex-shrink: 0; border-radius: 6px; overflow: hidden; box-shadow: 0 4px 10px rgba(0, 0, 0, 0.12); }
.book-img-link img { width: 120px; height: auto; display: block; }
.book-info h4 { font-size: 1.2rem; color: #0f172a; margin-bottom: 8px; }
.book-info ul { list-style-position: inside; color: #475569; font-size: 0.95rem; line-height: 1.6; }

/* 모바일 반응형 조절 */
@media (max-width: 600px) {
    .nav-item { font-size: 0.9rem; padding: 15px 10px; }
    .book-item { flex-direction: column; align-items: center; text-align: center; }
}