/* ==========================================================================
   기본 스타일 및 변수 설정 (Readability First)
   ========================================================================== */
:root {
    --primary-color: #ff8fa3; /* soft pink */
    --primary-hover: #ff6f8a;
    --primary-light: #fff5f8; /* very light pink background */
    --text-main: #1e293b; /* darker for contrast */
    --text-muted: #4b5563;
    --bg-main: #fff1f3; /* gentle pink canvas */
    --card-bg: #ffffff;
    --border-color: #e5e7eb;
    
    /* CRUD 색상 포인트 – keep original for functional clarity */
    --color-c: #10b981; /* Green */
    --color-r: #3b82f6; /* Blue */
    --color-u: #f59e0b; /* Amber */
    --color-d: #ef4444; /* Red */
    
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.04);
    --shadow-md: 0 3px 6px -1px rgba(0, 0, 0, 0.08), 0 2px 4px -1px rgba(0, 0, 0, 0.05);
    --radius-md: 12px;
    --radius-lg: 16px;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Noto Sans KR', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background-color: var(--bg-main);
    color: var(--text-main);
    line-height: 1.75;
    font-size: 17px;
    -webkit-font-smoothing: antialiased;
}

/* ==========================================================================
   레이아웃 및 컨테이너
   ========================================================================== */
.container {
    max-width: 1000px;
    margin: 0 auto;
    padding: 0 20px;
}

.scroll-margin {
    scroll-margin-top: 100px;
}

/* ==========================================================================
   헤더 및 네비게이션
   ========================================================================== */
.site-header {
    position: sticky;
    top: 0;
    z-index: 100;
    background-color: var(--primary-light);
    border-bottom: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
}

.header-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 70px;
}

.logo {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 20px;
    color: var(--text-main);
}

.logo-icon {
    font-size: 24px;
}

.main-nav ul {
    display: flex;
    list-style: none;
    gap: 12px;
}

.main-nav a {
    text-decoration: none;
    color: var(--text-muted);
    font-weight: 500;
    font-size: 15px;
    padding: 8px 14px;
    border-radius: 20px;
    transition: all 0.2s ease;
}

.main-nav a:hover,
.main-nav a.active {
    color: var(--primary-color);
    background-color: var(--primary-light);
}

/* ==========================================================================
   히어로 섹션
   ========================================================================== */
.hero-section {
    padding: 60px 0 40px;
    text-align: center;
    background: linear-gradient(180deg, #ffffff 0%, var(--bg-main) 100%);
    border-bottom: 1px solid var(--border-color);
}

.badge {
    display: inline-block;
    background-color: var(--primary-light);
    color: var(--primary-color);
    font-size: 14px;
    font-weight: 700;
    padding: 6px 16px;
    border-radius: 12px;
    margin-bottom: 16px;
}

.hero-section h1 {
    font-size: 36px;
    font-weight: 800;
    line-height: 1.4;
    letter-spacing: -0.3px;
    margin-bottom: 20px;
    color: var(--primary-color);
}

.highlight {
    color: var(--primary-color);
    position: relative;
    display: inline-block;
}

.hero-subtitle {
    font-size: 17px;
    color: var(--text-muted);
    max-width: 720px;
    margin: 0 auto 30px;
    word-break: keep-all;
}

.hero-actions {
    display: flex;
    justify-content: center;
    gap: 16px;
}

/* 버튼 공통 스타일 */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 10px 20px;
    font-size: 15px;
    font-weight: 600;
    text-decoration: none;
    border-radius: 12px;
    transition: all 0.2s ease;
    cursor: pointer;
    border: 2px solid transparent;
}

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

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

.btn-outline {
    background-color: #ffffff;
    color: var(--text-main);
    border-color: var(--border-color);
}

.btn-outline:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
    transform: translateY(-2px);
}

/* ==========================================================================
   메인 콘텐츠 카드
   ========================================================================== */
.content-wrapper {
    padding: 40px 20px 80px;
    display: flex;
    flex-direction: column;
    gap: 40px;
}

.content-card {
    background-color: var(--card-bg);
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    overflow: hidden;
    transition: box-shadow 0.3s ease;
}

.content-card:hover {
    box-shadow: var(--shadow-md);
}

.card-header {
    display: flex;
    align-items: center;
    gap: 16px;
    padding: 24px 32px;
    background-color: var(--primary-light);
    border-bottom: 1px solid var(--border-color);
}

.section-number {
    font-size: 18px;
    font-weight: 900;
    color: var(--primary-color);
    background-color: var(--primary-light);
    padding: 6px 14px;
    border-radius: 8px;
}

.card-header h2 {
    font-size: 26px;
    font-weight: 800;
    color: var(--text-main);
}

.card-body {
    padding: 36px;
}

.lead-text {
    font-size: 19px;
    font-weight: 400;
    color: #334155;
    margin-bottom: 30px;
    word-break: keep-all;
}

.sub-heading {
    font-size: 21px;
    font-weight: 700;
    margin: 36px 0 16px;
    color: var(--text-main);
    border-left: 4px solid var(--primary-color);
    padding-left: 12px;
}

/* 비유 박스 */
.analogy-box {
    display: flex;
    align-items: flex-start;
    gap: 20px;
    background-color: #fffbe6;
    border: 1px solid #ffe58f;
    border-radius: var(--radius-md);
    padding: 24px;
    margin-bottom: 30px;
}

.analogy-icon {
    font-size: 36px;
    line-height: 1;
}

.analogy-text h3 {
    font-size: 18px;
    color: #856404;
    margin-bottom: 6px;
}

.analogy-text p {
    font-size: 18px;
    color: #533f03;
    line-height: 1.6;
}

/* 비교 테이블 */
.comparison-table-wrapper {
    overflow-x: auto;
    margin: 24px 0 36px;
}

.comparison-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 16px;
    text-align: left;
}

.comparison-table th,
.comparison-table td {
    padding: 16px 20px;
    border-bottom: 1px solid var(--border-color);
}

.comparison-table th {
    background-color: #f1f5f9;
    font-weight: 700;
    color: var(--text-main);
}

.comparison-table tbody tr:hover {
    background-color: #f8fafc;
}

/* 주요 포인트 그리드 */
.key-points {
    margin-top: 40px;
}

.key-points h3 {
    font-size: 20px;
    margin-bottom: 20px;
}

.grid-3 {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 20px;
}

.point-item {
    background-color: var(--bg-main);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 24px;
    text-align: center;
}

.point-icon {
    font-size: 32px;
    margin-bottom: 12px;
}

.point-item h4 {
    font-size: 18px;
    margin-bottom: 8px;
    color: var(--text-main);
}

.point-item p {
    font-size: 15px;
    color: var(--text-muted);
}

/* ==========================================================================
   2. DB 종류 섹션
   ========================================================================== */
.grid-2 {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 24px;
    margin-bottom: 30px;
}

.type-card {
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    background-color: #ffffff;
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.type-header {
    padding: 24px;
    background-color: #f8fafc;
    border-bottom: 1px solid var(--border-color);
}

.type-badge {
    display: inline-block;
    font-size: 12px;
    font-weight: 700;
    color: var(--primary-color);
    background-color: var(--primary-light);
    padding: 4px 10px;
    border-radius: 12px;
    margin-bottom: 10px;
}

.type-badge.alt {
    color: #d97706;
    background-color: #fef3c7;
}

.type-header h3 {
    font-size: 22px;
    margin-bottom: 6px;
}

.type-desc {
    font-size: 15px;
    color: var(--text-muted);
}

.type-body {
    padding: 24px;
    flex-grow: 1;
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.concept-visual {
    background-color: #f1f5f9;
    padding: 14px;
    border-radius: 8px;
    font-size: 14px;
}

.mini-table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 8px;
    background-color: #ffffff;
}

.mini-table th, .mini-table td {
    border: 1px solid var(--border-color);
    padding: 6px 10px;
    text-align: center;
    font-size: 13px;
}

.json-visual pre {
    font-family: monospace;
    font-size: 13px;
    color: #0f172a;
    background-color: #ffffff;
    padding: 10px;
    border-radius: 6px;
    border: 1px solid var(--border-color);
    margin-top: 6px;
}

.feature-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 10px;
    font-size: 15px;
}

.feature-list li {
    position: relative;
    padding-left: 18px;
}

.feature-list li::before {
    content: "•";
    position: absolute;
    left: 0;
    color: var(--primary-color);
    font-weight: bold;
}

.extra-db-info {
    background-color: #f0fdf4;
    border: 1px solid #bbf7d0;
    padding: 20px 24px;
    border-radius: var(--radius-md);
}

.extra-db-info h3 {
    color: #166534;
    font-size: 17px;
    margin-bottom: 6px;
}

.extra-db-info p {
    color: #14532d;
    font-size: 15px;
}

/* ==========================================================================
   3. DB 사용법 (CRUD)
   ========================================================================== */
.crud-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 20px;
    margin: 24px 0 36px;
}

.crud-card {
    display: flex;
    flex-direction: column;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 20px;
    background-color: #ffffff;
    position: relative;
    overflow: hidden;
}

.crud-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 4px;
}

.crud-card.create::before { background-color: var(--color-c); }
.crud-card.read::before { background-color: var(--color-r); }
.crud-card.update::before { background-color: var(--color-u); }
.crud-card.delete::before { background-color: var(--color-d); }

.crud-letter {
    font-size: 32px;
    font-weight: 900;
    margin-bottom: 10px;
}

.create .crud-letter { color: var(--color-c); }
.read .crud-letter { color: var(--color-r); }
.update .crud-letter { color: var(--color-u); }
.delete .crud-letter { color: var(--color-d); }

.crud-details h4 {
    font-size: 17px;
    margin-bottom: 4px;
}

.crud-tag {
    display: inline-block;
    font-size: 12px;
    font-weight: 700;
    color: var(--text-muted);
    background-color: #f1f5f9;
    padding: 2px 8px;
    border-radius: 4px;
    margin-bottom: 10px;
}

.crud-details p {
    font-size: 14px;
    color: var(--text-muted);
    line-height: 1.5;
}

.sql-intro {
    background-color: #1e293b;
    color: #f8fafc;
    padding: 28px;
    border-radius: var(--radius-md);
}

.sql-intro h3 {
    color: #60a5fa;
    font-size: 19px;
    margin-bottom: 10px;
}

.sql-intro p {
    color: #cbd5e1;
    font-size: 15px;
    margin-bottom: 20px;
}

.sql-examples {
    background-color: #0f172a;
    padding: 18px 22px;
    border-radius: 8px;
    border: 1px solid #334155;
}

.sql-label {
    display: block;
    font-size: 12px;
    color: #94a3b8;
    margin-bottom: 6px;
}

.sql-examples code {
    display: block;
    font-family: monospace;
    font-size: 16px;
    color: #4ade80;
    margin-bottom: 8px;
}

.sql-explain {
    color: #e2e8f0 !important;
    font-size: 14px !important;
    margin-bottom: 0 !important;
}

/* ==========================================================================
   4. 인터랙티브 시뮬레이터 & 퀴즈
   ========================================================================== */
.highlight-card {
    border: 2px solid #bfdbfe;
}

.simulator-container {
    background-color: #f8fafc;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 24px;
    margin-bottom: 40px;
}

.simulator-controls h4 {
    font-size: 16px;
    margin-bottom: 12px;
    color: var(--text-main);
}

.button-group {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin-bottom: 24px;
}

.sim-btn {
    padding: 10px 18px;
    font-size: 14px;
    font-weight: 700;
    border-radius: 8px;
    border: 1px solid transparent;
    cursor: pointer;
    transition: all 0.2s ease;
}

.btn-c { background-color: var(--color-c); color: white; }
.btn-c:hover { background-color: #059669; }

.btn-r { background-color: var(--color-r); color: white; }
.btn-r:hover { background-color: #2563eb; }

.btn-u { background-color: var(--color-u); color: white; }
.btn-u:hover { background-color: #d97706; }

.btn-d { background-color: var(--color-d); color: white; }
.btn-d:hover { background-color: #dc2626; }

.btn-reset { background-color: #64748b; color: white; }
.btn-reset:hover { background-color: #475569; }

.simulator-screen {
    background-color: #ffffff;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    overflow: hidden;
}

.screen-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    background-color: #f1f5f9;
    padding: 12px 18px;
    border-bottom: 1px solid var(--border-color);
}

.screen-title {
    font-size: 14px;
    font-weight: 700;
    color: var(--text-main);
}

.log-status {
    font-size: 13px;
    color: var(--primary-color);
    font-weight: 500;
}

.interactive-db-table {
    width: 100%;
    border-collapse: collapse;
    text-align: center;
    font-size: 15px;
}

.interactive-db-table th {
    background-color: #f8fafc;
    padding: 12px;
    border-bottom: 1px solid var(--border-color);
    color: var(--text-muted);
    font-size: 13px;
}

.interactive-db-table td {
    padding: 14px 12px;
    border-bottom: 1px solid var(--border-color);
    transition: background-color 0.3s ease;
}

/* 테이블 애니메이션 상태 */
.row-highlight {
    background-color: #dbeafe !important;
}

.row-new {
    animation: flashGreen 1s ease;
}

@keyframes flashGreen {
    0% { background-color: #a7f3d0; }
    100% { background-color: #ffffff; }
}

.row-updated {
    animation: flashYellow 1s ease;
}

@keyframes flashYellow {
    0% { background-color: #fde68a; }
    100% { background-color: #ffffff; }
}

/* 퀴즈 스타일 */
.quiz-container {
    background-color: #f1f5f9;
    padding: 28px;
    border-radius: var(--radius-md);
}

.quiz-container h3 {
    font-size: 20px;
    margin-bottom: 6px;
}

.quiz-intro {
    font-size: 15px;
    color: var(--text-muted);
    margin-bottom: 24px;
}

.quiz-item {
    background-color: #ffffff;
    padding: 20px;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    margin-bottom: 16px;
}

.quiz-question {
    font-weight: 700;
    font-size: 16px;
    margin-bottom: 14px;
}

.quiz-options {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.quiz-opt {
    padding: 8px 16px;
    font-size: 14px;
    background-color: var(--bg-main);
    border: 1px solid var(--border-color);
    border-radius: 20px;
    cursor: pointer;
    transition: all 0.2s ease;
}

.quiz-opt:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
}

.quiz-opt.correct-clicked {
    background-color: #10b981;
    color: white;
    border-color: #10b981;
}

.quiz-opt.wrong-clicked {
    background-color: #ef4444;
    color: white;
    border-color: #ef4444;
}

.quiz-feedback {
    margin-top: 12px;
    font-size: 14px;
    font-weight: 700;
}

.quiz-feedback.success { color: #10b981; }
.quiz-feedback.error { color: #ef4444; }

/* ==========================================================================
   푸터
   ========================================================================== */
.site-footer {
    background-color: #0f172a;
    color: #94a3b8;
    text-align: center;
    padding: 30px 20px;
    font-size: 14px;
    border-top: 1px solid #1e293b;
}

.copyright {
    margin-top: 6px;
    font-size: 13px;
    color: #64748b;
}

/* ==========================================================================
   반응형 웹 스타일 (Mobile Friendly)
   ========================================================================== */
@media (max-width: 768px) {
    .header-container {
        flex-direction: column;
        height: auto;
        padding: 12px 20px;
        gap: 10px;
    }

    .main-nav ul {
        flex-wrap: wrap;
        justify-content: center;
    }

    .hero-section h1 {
        font-size: 28px;
    }

    .hero-subtitle {
        font-size: 16px;
    }

    .card-header {
        padding: 20px;
    }

    .card-body {
        padding: 20px;
    }

    .analogy-box {
        flex-direction: column;
        gap: 10px;
    }

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

    .button-group {
        flex-direction: column;
    }

    .sim-btn {
        width: 100%;
    }
}