:root {
    --bg: #ffffff;
    --surface: #f7f7f6;
    --card: #ffffff;
    --text: #37352f;
    --muted: #6f6b67;
    --line: #e9e7e5;
    --accent: #2383e2;
    --accent-soft: #eaf4ff;
    --radius: 8px;
    --shadow: 0 8px 24px rgba(24, 24, 24, 0.06);
}

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

body {
    font-family: Inter, Pretendard, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
    font-size: 18px;
    line-height: 1.7;
    color: var(--text);
    background: linear-gradient(180deg, #ffffff 0%, #fcfcfb 100%);
}

.container {
    max-width: 720px;
    min-height: 100vh;
    margin: 0 auto;
    padding: 28px 20px 56px;
    background: var(--bg);
}

header {
    text-align: left;
    border-bottom: 1px solid var(--line);
    padding: 12px 0 20px;
}

header h1 {
    font-size: 2rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    color: var(--text);
    margin-bottom: 6px;
}

header p {
    font-size: 1rem;
    color: var(--muted);
}

main {
    padding: 24px 0 0;
}

/* Detail Top Header */
.detail-page-header {
    display: flex;
    align-items: center;
    justify-content: flex-start;
    border-bottom: 1px solid var(--line);
    padding: 6px 0 14px;
    margin-bottom: 10px;
}

.detail-back-link {
    color: var(--muted);
    font-size: 0.88rem;
    font-weight: 600;
    text-decoration: none;
    border: 1px solid var(--line);
    border-radius: 999px;
    padding: 7px 12px;
    background: #fff;
}

.detail-back-link:hover {
    border-color: #cfcac5;
    color: var(--text);
    background: #fcfcfc;
}

/* Category Nav */
.category-nav {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
    margin-top: 18px;
    margin-bottom: 14px;
}

.category-btn {
    border: 1px solid var(--line);
    background: #fff;
    color: var(--muted);
    border-radius: 999px;
    padding: 9px 16px;
    font-size: 0.92rem;
    font-weight: 600;
    line-height: 1;
    cursor: pointer;
    transition: all 0.2s ease;
}

.category-btn:hover {
    border-color: #cfcac5;
    color: var(--text);
    background: #fcfcfc;
}

.category-btn.active {
    background: var(--accent);
    border-color: var(--accent);
    color: #fff;
}

.category-description {
    background: var(--surface);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    padding: 14px 16px;
    margin-bottom: 10px;
}

.category-description p {
    margin: 0;
    color: var(--muted);
    font-size: 0.95rem;
}

/* Common */
section {
    margin: 24px 0;
    padding: 20px;
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: var(--card);
}

section h3 {
    font-size: 1.18rem;
    margin-bottom: 14px;
    letter-spacing: -0.01em;
}

section h4 {
    font-size: 1rem;
    margin: 18px 0 10px;
    color: var(--muted);
    font-weight: 600;
}

.badge-container {
    display: flex;
    gap: 8px;
    align-items: center;
    flex-wrap: wrap;
    margin-bottom: 12px;
}

.difficulty,
.difficulty-badge,
.category-badge {
    display: inline-block;
    border-radius: 999px;
    font-size: 0.82rem;
    font-weight: 700;
}

.difficulty-badge {
    padding: 4px 11px;
    background: var(--accent-soft);
    color: var(--accent);
    border: 1px solid #cfe5fb;
}

.category-badge {
    padding: 4px 11px;
    background: #f1f1f0;
    color: #5a5753;
    border: 1px solid #e4e2df;
}

.difficulty-badge.level-1,
.difficulty-badge.level-2,
.difficulty-badge.level-3 {
    background: #e9f7ee;
    color: #19734a;
    border-color: #cdeedb;
}

.difficulty-badge.level-4,
.difficulty-badge.level-5,
.difficulty-badge.level-6 {
    background: var(--accent-soft);
    color: var(--accent);
    border-color: #cfe5fb;
}

.difficulty-badge.level-7,
.difficulty-badge.level-8 {
    background: #fff4e6;
    color: #a15e00;
    border-color: #ffe1b8;
}

.difficulty-badge.level-9,
.difficulty-badge.level-10 {
    background: #fdeeee;
    color: #a12626;
    border-color: #f9d1d1;
}

.no-data {
    color: var(--muted);
    font-style: italic;
}

/* List Page */
.post-list {
    display: grid;
    grid-template-columns: 1fr;
    gap: 14px;
    margin-top: 16px;
}

.post-card {
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: #fff;
    padding: 16px 16px 14px;
    cursor: pointer;
    transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}

.post-card:hover {
    transform: translateY(-2px);
    border-color: #d2ceca;
    box-shadow: var(--shadow);
}

.post-title {
    font-size: 1.2rem;
    line-height: 1.45;
    margin: 2px 0 10px;
    letter-spacing: -0.01em;
    color: var(--text);
}

.post-summary {
    color: var(--muted);
    font-size: 0.94rem;
    line-height: 1.65;
    margin: 0 0 12px;
    display: -webkit-box;
    -webkit-line-clamp: 3;
    line-clamp: 3;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.post-date {
    border-top: 1px solid #f0eeec;
    padding-top: 10px;
    font-size: 0.82rem;
    color: #9b9690;
}

.no-posts {
    text-align: center;
    padding: 54px 12px;
    color: var(--muted);
}

.no-posts p {
    margin: 6px 0;
    font-size: 0.98rem;
}

/* Detail Page */
.section-header {
    background: #fff;
}

.section-header h2 {
    font-size: 1.72rem;
    line-height: 1.35;
    margin-bottom: 8px;
    letter-spacing: -0.015em;
}

.hook {
    margin-top: 10px;
    color: var(--accent);
    font-weight: 700;
    font-size: 1.02rem;
}

.summary {
    margin-top: 10px;
    color: var(--muted);
    font-size: 1rem;
}

.words-grid,
.expressions-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 10px;
    margin-top: 8px;
}

.word-card,
.expression-card {
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: #fff;
    padding: 12px 13px;
}

.word-term,
.expr-term {
    font-weight: 700;
    margin-bottom: 4px;
}

.word-pronunciation,
.word-example,
.expr-example {
    color: var(--muted);
    font-size: 0.9rem;
}

.word-meaning,
.expr-meaning {
    font-size: 0.95rem;
    margin-bottom: 4px;
}

.section-content,
.section-quiz,
.section-explanations,
.section-korean,
.section-source {
    background: #fff;
}

.content-text,
.korean-text {
    white-space: pre-wrap;
    font-size: 0.98rem;
    color: var(--text);
}

.quiz-item {
    border: 1px solid var(--line);
    border-radius: var(--radius);
    padding: 14px;
    margin-bottom: 12px;
    background: #fff;
}

.quiz-question {
    font-weight: 700;
    margin-bottom: 10px;
    font-size: 0.98rem;
}

.quiz-option {
    width: 100%;
    border: 1px solid var(--line);
    background: #fff;
    border-radius: var(--radius);
    padding: 10px 11px;
    margin-bottom: 8px;
    text-align: left;
    cursor: pointer;
    font-size: 0.93rem;
    color: var(--text);
}

.quiz-option:hover {
    border-color: #cfd7e0;
    background: #f9fbff;
}

.quiz-option:disabled {
    cursor: not-allowed;
}

.quiz-option.correct {
    border-color: #5db98a;
    background: #ecf8f1;
    color: #1e6f48;
    font-weight: 700;
}

.quiz-option.incorrect {
    border-color: #df6b6b;
    background: #fff1f1;
    color: #9f1f1f;
}

.quiz-feedback {
    border-radius: var(--radius);
    padding: 10px 11px;
    background: var(--surface);
    margin-top: 8px;
    font-size: 0.9rem;
    color: var(--muted);
}

.quiz-feedback.correct {
    background: #eaf7f0;
    color: #1e6f48;
    font-weight: 700;
}

.quiz-feedback.incorrect {
    background: #fff1f1;
    color: #9f1f1f;
    font-weight: 700;
}

.explanation-item {
    border-left: 3px solid var(--accent);
    background: #fafdff;
    border: 1px solid #dfe9f5;
    border-radius: 8px;
    padding: 14px;
    margin-bottom: 12px;
}

.explanation-sentence {
    border: 1px solid #cfe5fb;
    border-radius: 8px;
    background: #edf6ff;
    color: #1c3552;
    padding: 11px 12px;
    margin-bottom: 10px;
    font-size: 0.95rem;
    line-height: 1.65;
    font-weight: 600;
}

.explanation-points {
    display: grid;
    gap: 8px;
}

.explanation-point {
    margin: 0;
    border: 1px solid #e9ecef;
    border-radius: 7px;
    background: #ffffff;
    padding: 9px 11px;
    white-space: pre-wrap;
    line-height: 1.75;
    font-size: 0.93rem;
    color: #45413d;
}

.section-source {
    text-align: center;
}

.source-link {
    display: inline-block;
    border-radius: var(--radius);
    text-decoration: none;
    padding: 10px 16px;
    background: var(--accent);
    color: #fff;
    font-size: 0.92rem;
    font-weight: 700;
}

.source-link:hover {
    filter: brightness(0.95);
}

.section-related {
    background: #fff;
}

.related-list {
    display: grid;
    gap: 10px;
}

.related-groups {
    display: grid;
    gap: 16px;
}

.related-group {
    border: 1px solid var(--line);
    border-radius: var(--radius);
    padding: 12px;
    background: #fcfcfc;
}

.related-group-title {
    font-size: 0.9rem;
    color: #6b6660;
    margin: 0 0 10px;
    font-weight: 700;
}

.related-item {
    display: block;
    border: 1px solid var(--line);
    border-radius: var(--radius);
    padding: 12px 13px;
    text-decoration: none;
    color: var(--text);
    background: #fff;
    transition: border-color 0.2s ease, box-shadow 0.2s ease, transform 0.2s ease;
}

.related-item:hover {
    border-color: #d2ceca;
    box-shadow: var(--shadow);
    transform: translateY(-1px);
}

.related-meta {
    display: flex;
    gap: 8px;
    margin-bottom: 8px;
    align-items: center;
    flex-wrap: wrap;
}

.related-title {
    font-size: 0.98rem;
    font-weight: 700;
    line-height: 1.45;
    margin-bottom: 6px;
}

.related-date {
    font-size: 0.82rem;
    color: #9b9690;
}

.detail-bottom-actions {
    margin-top: 12px;
    display: flex;
    justify-content: flex-start;
}

/* Loading */
.spinner-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 64px 20px;
}

.spinner {
    width: 42px;
    height: 42px;
    border: 3px solid #e9edf2;
    border-top: 3px solid var(--accent);
    border-radius: 50%;
    animation: spin 0.9s linear infinite;
}

@keyframes spin {
    from {
        transform: rotate(0);
    }

    to {
        transform: rotate(360deg);
    }
}

.spinner-container p {
    margin-top: 14px;
    font-size: 0.9rem;
    color: var(--muted);
}

/* Load More */
.load-more-container {
    display: flex;
    justify-content: center;
    margin-top: 28px;
}

.load-more-btn {
    border: 1px solid #cfe0f4;
    background: #f4f9ff;
    color: #1d5f9e;
    border-radius: var(--radius);
    padding: 11px 20px;
    font-size: 0.9rem;
    font-weight: 700;
    cursor: pointer;
}

.load-more-btn:hover {
    background: #edf5ff;
}

.load-more-btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

/* Mobile */
@media (max-width: 768px) {
    body {
        font-size: 16px;
    }

    .container {
        padding: 16px 14px 36px;
    }

    header h1 {
        font-size: 1.62rem;
    }

    section {
        padding: 15px;
        margin: 16px 0;
    }

    .section-header h2 {
        font-size: 1.35rem;
    }

    .detail-page-header {
        padding-top: 2px;
    }
}