:root {
    --primary: #0288d1; /* Water Blue */
    --secondary: #43a047; /* Nature Green */
    --bg-light: #f5f9fc;
    --text-dark: #37474f;
    --text-light: #78909c;
    --white: #ffffff;
    --shadow: 0 4px 12px rgba(0,0,0,0.08);
}

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

body {
    font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, system-ui, sans-serif;
    background-color: var(--bg-light);
    color: var(--text-dark);
    line-height: 1.6;
}

.container {
    max-width: 900px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
.app-header {
    background: var(--white);
    padding: 15px 0;
    box-shadow: 0 2px 4px rgba(0,0,0,0.05);
    position: sticky;
    top: 0;
    z-index: 100;
}

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

.logo {
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--primary);
    cursor: pointer;
}

.app-header nav a {
    text-decoration: none;
    color: var(--text-dark);
    margin-left: 20px;
    font-weight: 600;
}

/* Ad Containers */
.ad-container {
    background: #e1e8ed;
    text-align: center;
    padding: 10px;
    margin: 20px auto;
    max-width: 900px;
    border-radius: 8px;
    min-height: 100px; /* Placeholder height */
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

.ad-label {
    font-size: 0.7rem;
    color: #999;
    margin-bottom: 5px;
    text-align: right;
    width: 100%;
    padding-right: 10px;
}

/* Hero Section */
.hero {
    text-align: center;
    padding: 60px 20px;
    background: linear-gradient(135deg, #e3f2fd 0%, #ffffff 100%);
    border-radius: 0 0 20px 20px;
    margin-bottom: 40px;
}

.hero h2 {
    font-size: 2.2rem;
    margin-bottom: 10px;
    color: var(--text-dark);
}

.hero p {
    font-size: 1.1rem;
    color: var(--text-light);
    margin-bottom: 30px;
}

/* Theme Cards */
.theme-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 15px;
    max-width: 800px;
    margin: 0 auto;
}

.theme-card {
    background: var(--white);
    padding: 20px;
    border-radius: 12px;
    text-align: center;
    box-shadow: var(--shadow);
    cursor: pointer;
    transition: transform 0.2s;
    border: 1px solid transparent;
}

.theme-card:hover {
    transform: translateY(-3px);
    border-color: var(--primary);
}

.theme-icon {
    font-size: 2rem;
    margin-bottom: 10px;
    display: block;
}

/* List View */
.filters {
    display: flex;
    gap: 10px;
    overflow-x: auto;
    padding-bottom: 10px;
    margin-bottom: 20px;
}

.filter-btn {
    padding: 8px 16px;
    background: var(--white);
    border: 1px solid #ddd;
    border-radius: 20px;
    cursor: pointer;
    white-space: nowrap;
}

.filter-btn.active {
    background: var(--primary);
    color: var(--white);
    border-color: var(--primary);
}

.valley-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 20px;
}

.valley-card {
    background: var(--white);
    border-radius: 12px;
    overflow: hidden;
    box-shadow: var(--shadow);
    cursor: pointer;
    transition: transform 0.2s;
}

.valley-card:hover {
    transform: translateY(-5px);
}

.card-img-placeholder {
    height: 180px;
    background: #cfd8dc;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #90a4ae;
}

.card-body {
    padding: 20px;
}

.card-tags {
    display: flex;
    gap: 5px;
    margin-bottom: 10px;
}

.tag {
    font-size: 0.75rem;
    padding: 3px 8px;
    border-radius: 4px;
    background: #e3f2fd;
    color: var(--primary);
}

/* Detail View */
.detail-header {
    margin-bottom: 30px;
}

.detail-title {
    font-size: 2rem;
    margin-bottom: 10px;
}

.detail-meta {
    display: flex;
    gap: 15px;
    color: var(--text-light);
    font-size: 0.9rem;
}

/* Visual Depth Meter */
.depth-visual-container {
    background: var(--white);
    padding: 30px;
    border-radius: 16px;
    box-shadow: var(--shadow);
    margin-bottom: 40px;
    text-align: center;
}

.depth-title {
    font-size: 1.2rem;
    margin-bottom: 20px;
    font-weight: 700;
}

.depth-meter {
    display: flex;
    align-items: flex-end;
    justify-content: center;
    height: 200px;
    gap: 20px;
    position: relative;
    max-width: 400px;
    margin: 0 auto;
}

.human-silhouette {
    width: 60px;
    height: 180px;
    background: #b0bec5;
    mask: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="black"><path d="M12 2C13.1 2 14 2.9 14 4S13.1 6 12 6 10 5.1 10 4 10.9 2 12 2M12 22C11.4 22 11 21.6 11 21V16H8C7.4 16 7 15.6 7 15V9C7 8.4 7.4 8 8 8H16C16.6 8 17 8.4 17 9V15C17 15.6 16.6 16 16 16H13V21C13 21.6 12.6 22 12 22Z"/></svg>') no-repeat center;
    -webkit-mask: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="black"><path d="M12 2C13.1 2 14 2.9 14 4S13.1 6 12 6 10 5.1 10 4 10.9 2 12 2M12 22C11.4 22 11 21.6 11 21V16H8C7.4 16 7 15.6 7 15V9C7 8.4 7.4 8 8 8H16C16.6 8 17 8.4 17 9V15C17 15.6 16.6 16 16 16H13V21C13 21.6 12.6 22 12 22Z"/></svg>') no-repeat center;
    mask-size: contain;
    -webkit-mask-size: contain;
}

.water-level {
    width: 100px;
    background: linear-gradient(180deg, #4fc3f7 0%, #0288d1 100%);
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    opacity: 0.7;
    border-radius: 4px 4px 0 0;
    transition: height 1s ease-out;
    z-index: 1;
}

.human-silhouette {
    z-index: 2;
    background-color: #546e7a;
}

/* Essay Section */
.essay-section {
    max-width: 680px;
    margin: 0 auto 40px;
    padding: 0 20px;
    font-family: 'KoPub Batang', serif; /* Fallback will invoke serif */
}

.essay-content {
    font-size: 1.15rem;
    line-height: 1.8;
    color: #455a64;
    text-align: justify;
}

.essay-quote {
    font-size: 1.4rem;
    font-style: italic;
    color: var(--primary);
    text-align: center;
    margin: 40px 0;
    font-weight: 700;
}

/* Info Table */
.info-table {
    width: 100%;
    border-collapse: collapse;
    background: var(--white);
    border-radius: 12px;
    overflow: hidden;
    box-shadow: var(--shadow);
    margin-bottom: 40px;
}

.info-table th, .info-table td {
    padding: 15px 20px;
    border-bottom: 1px solid #eceff1;
    text-align: left;
}

.info-table th {
    background: #f4f6f8;
    color: var(--text-light);
    width: 30%;
    font-weight: 600;
}

/* Footer */
.app-footer {
    background: #263238;
    color: #eceff1;
    text-align: center;
    padding: 40px 0;
    margin-top: 60px;
}

/* Utilities */
.btn-back {
    display: inline-block;
    margin-bottom: 20px;
    color: var(--text-light);
    cursor: pointer;
    font-size: 0.9rem;
}

@media (max-width: 600px) {
    .hero h2 { font-size: 1.8rem; }
    .theme-grid { grid-template-columns: repeat(2, 1fr); }
    .info-table th, .info-table td { display: block; width: 100%; }
    .info-table th { background: #fff; padding-bottom: 5px; color: var(--primary); }
    .info-table td { padding-top: 0; }
}