/* ===== MathHub Global - Common Styles ===== */

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

/* Base */
body {
    font-family: 'Noto Sans KR', Arial, sans-serif;
    background-color: #f5f5f5;
    line-height: 1.8;
    color: #333;
}

/* ===== Global Navigation ===== */
.global-nav {
    background: #1a1a2e;
    padding: 0 20px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 50px;
    position: sticky;
    top: 0;
    z-index: 1000;
}
.global-nav .nav-brand {
    color: #fff;
    font-weight: 700;
    font-size: 1.1em;
    text-decoration: none;
}
.global-nav .nav-links {
    display: flex;
    gap: 0;
    list-style: none;
    height: 100%;
}
.global-nav .nav-links a {
    color: rgba(255,255,255,0.7);
    text-decoration: none;
    padding: 0 16px;
    height: 50px;
    display: flex;
    align-items: center;
    font-size: 0.9em;
    font-weight: 500;
    transition: all 0.2s;
    border-bottom: 2px solid transparent;
}
.global-nav .nav-links a:hover,
.global-nav .nav-links a.active {
    color: #fff;
    border-bottom-color: #667eea;
    background: rgba(255,255,255,0.05);
}
.global-nav .nav-cta {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: #fff !important;
    border-radius: 20px;
    padding: 6px 16px !important;
    font-size: 0.85em !important;
    height: auto !important;
    border-bottom: none !important;
}
.global-nav .nav-cta:hover {
    opacity: 0.9;
    background: linear-gradient(135deg, #764ba2 0%, #667eea 100%) !important;
}

/* ===== Header ===== */
.header {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 40px 20px;
    text-align: center;
}
.header h1 {
    font-size: 2.2em;
    margin-bottom: 10px;
}
.header p {
    font-size: 1.1em;
    opacity: 0.9;
}

/* ===== Category Badge ===== */
.category-badge {
    display: inline-block;
    background-color: rgba(255,255,255,0.2);
    padding: 5px 15px;
    border-radius: 20px;
    font-size: 0.9em;
    margin-bottom: 15px;
}

/* ===== Post Page Container ===== */
.container {
    max-width: 900px;
    margin: 40px auto;
    background: white;
    padding: 50px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    border-radius: 8px;
}

/* ===== Back Link ===== */
.back-link {
    display: inline-block;
    margin-bottom: 30px;
    color: #667eea;
    text-decoration: none;
    font-weight: 600;
}
.back-link:hover { text-decoration: underline; }

/* ===== Typography ===== */
h2 {
    color: #2c3e50;
    margin-top: 40px;
    margin-bottom: 20px;
    padding-bottom: 10px;
    border-bottom: 2px solid #667eea;
}
h3 {
    color: #34495e;
    margin-top: 30px;
    margin-bottom: 15px;
}
h4 {
    color: #555;
    margin-top: 20px;
    margin-bottom: 10px;
}
p {
    margin-bottom: 15px;
    text-align: justify;
}
ul, ol {
    margin-left: 30px;
    margin-bottom: 15px;
}
li { margin-bottom: 8px; }

/* ===== Content Boxes ===== */
.definition-box {
    background-color: #e7f3ff;
    border-left: 4px solid #2196F3;
    padding: 20px;
    margin: 25px 0;
    border-radius: 4px;
}
.definition-box h4 { color: #1976D2; margin-top: 0; margin-bottom: 15px; }

.theorem-box {
    background-color: #fff3cd;
    border-left: 4px solid #ffc107;
    padding: 20px;
    margin: 25px 0;
    border-radius: 4px;
}
.theorem-box h4 { color: #f57c00; margin-top: 0; margin-bottom: 15px; }

.example-box {
    background-color: #f0f9ff;
    border-left: 4px solid #0ea5e9;
    padding: 20px;
    margin: 25px 0;
    border-radius: 4px;
}
.example-box h4 { color: #0284c7; margin-top: 0; margin-bottom: 15px; }

.step-box {
    background-color: #f0fdf4;
    border-left: 4px solid #22c55e;
    padding: 20px;
    margin: 25px 0;
    border-radius: 4px;
}
.step-box h4 { color: #16a34a; margin-top: 0; margin-bottom: 15px; }

.summary-box {
    background-color: #f3e5f5;
    border: 2px solid #9c27b0;
    padding: 20px;
    margin: 30px 0;
    border-radius: 4px;
}
.summary-box h4 { color: #7b1fa2; margin-top: 0; margin-bottom: 15px; }

.problem-box {
    background-color: #f1f5f9;
    border-left: 4px solid #64748b;
    padding: 20px;
    margin: 25px 0;
    border-radius: 4px;
}
.problem-box h4 { color: #475569; margin-top: 0; margin-bottom: 15px; }

.solution-box {
    background-color: #f0fdf4;
    border-left: 4px solid #22c55e;
    padding: 20px;
    margin: 25px 0;
    border-radius: 4px;
}
.solution-box h4 { color: #16a34a; margin-top: 0; margin-bottom: 15px; }

/* ===== Formula & Highlight ===== */
.formula {
    background-color: #f8f9fa;
    padding: 15px;
    border-radius: 5px;
    margin: 15px 0;
    overflow-x: auto;
}
.highlight {
    background-color: #fff9c4;
    padding: 2px 5px;
    border-radius: 3px;
    font-weight: 600;
}

/* ===== Footer ===== */
.footer {
    text-align: center;
    padding: 30px 20px;
    color: #666;
    margin-top: 50px;
}

/* ===== CTA Banner ===== */
.cta-banner {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 24px 30px;
    border-radius: 12px;
    margin: 30px 0;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 20px;
}
.cta-banner p {
    margin: 0;
    font-size: 1.05em;
    text-align: left;
}
.cta-banner .cta-btn {
    background: white;
    color: #667eea;
    padding: 10px 24px;
    border-radius: 25px;
    text-decoration: none;
    font-weight: 700;
    white-space: nowrap;
    transition: transform 0.2s;
}
.cta-banner .cta-btn:hover {
    transform: scale(1.05);
}

/* ===== Date ===== */
.date {
    opacity: 0.9;
    font-size: 0.95em;
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
    .container {
        padding: 30px 20px;
        margin: 20px;
    }
    .header h1 { font-size: 1.8em; }
    .global-nav { padding: 0 10px; }
    .global-nav .nav-links a { padding: 0 10px; font-size: 0.85em; }
    .cta-banner { flex-direction: column; text-align: center; }
}