/* ===== RESET & BASE ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html {
    font-size: 16px;
    -webkit-text-size-adjust: 100%;
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
                 "Helvetica Neue", Arial, sans-serif;
    line-height: 1.6;
    color: #2d2d2d;
    background: #f8f9fa;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

a { color: #0066cc; text-decoration: none; }
a:hover { text-decoration: underline; }

img { max-width: 100%; height: auto; }

/* ===== LAYOUT ===== */
.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1.5rem;
}

/* ===== HEADER ===== */
.site-header {
    background: #1a1a2e;
    color: #ffffff;
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: 0 2px 8px rgba(0,0,0,0.15);
}

.site-header .container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.site-logo {
    font-size: 1.35rem;
    font-weight: 700;
    color: #ffffff;
    letter-spacing: -0.02em;
}
.site-logo:hover { text-decoration: none; }
.site-logo span { color: #4da6ff; }

.site-nav { display: flex; gap: 1.5rem; align-items: center; }
.site-nav a { color: #ccd6e0; font-size: 0.95rem; }
.site-nav a:hover { color: #ffffff; text-decoration: none; }

/* ===== HERO ===== */
.hero {
    background: linear-gradient(135deg, #1a1a2e 0%, #16213e 50%, #0f3460 100%);
    color: #ffffff;
    padding: 4rem 0 3.5rem;
    text-align: center;
}

.hero h1 {
    font-size: 2.6rem;
    font-weight: 800;
    line-height: 1.15;
    margin-bottom: 1rem;
    letter-spacing: -0.03em;
}

.hero p {
    font-size: 1.2rem;
    color: #b0c4de;
    max-width: 640px;
    margin: 0 auto;
}

/* ===== BREADCRUMB ===== */
.breadcrumb {
    padding: 1rem 0 0.5rem;
    font-size: 0.875rem;
    color: #6c757d;
}
.breadcrumb a { color: #0066cc; }
.breadcrumb .sep { margin: 0 0.4rem; color: #adb5bd; }

/* ===== SECTION TITLES ===== */
.section-title {
    font-size: 1.75rem;
    font-weight: 700;
    color: #1a1a2e;
    margin-bottom: 1.5rem;
    padding-bottom: 0.5rem;
    border-bottom: 3px solid #0066cc;
    display: inline-block;
}

/* ===== CARD GRID ===== */
.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 1.5rem;
    margin-bottom: 2rem;
}

.card {
    background: #ffffff;
    border: 1px solid #e2e8f0;
    border-radius: 12px;
    padding: 1.75rem;
    transition: transform 0.15s ease, box-shadow 0.15s ease;
    display: flex;
    flex-direction: column;
}

.card:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 24px rgba(0,0,0,0.1);
}

.card-icon {
    font-size: 2.2rem;
    margin-bottom: 0.75rem;
}

.card h3 {
    font-size: 1.15rem;
    font-weight: 600;
    color: #1a1a2e;
    margin-bottom: 0.5rem;
}

.card p {
    font-size: 0.925rem;
    color: #555;
    flex: 1;
}

.card .card-meta {
    margin-top: 0.75rem;
    font-size: 0.8rem;
    color: #8895a7;
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: 0.04em;
}

.card a.card-link {
    display: block;
    color: inherit;
    text-decoration: none;
    height: 100%;
}
.card a.card-link:hover { text-decoration: none; }

/* ===== CALCULATOR PAGE LAYOUT ===== */
.calc-layout {
    display: grid;
    grid-template-columns: 1fr 320px;
    gap: 2rem;
    padding: 2rem 0;
}

.calc-main { min-width: 0; }

.calc-sidebar {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

/* ===== CALCULATOR FORM ===== */
.calc-form-section {
    background: #ffffff;
    border: 1px solid #e2e8f0;
    border-radius: 12px;
    padding: 2rem;
    margin-bottom: 1.5rem;
}

.calc-form-section h1 {
    font-size: 1.85rem;
    font-weight: 700;
    color: #1a1a2e;
    margin-bottom: 0.5rem;
}

.calc-description {
    color: #555;
    margin-bottom: 1.75rem;
    font-size: 1rem;
    line-height: 1.7;
}

.form-group {
    margin-bottom: 1.25rem;
}

.form-group label {
    display: block;
    font-weight: 600;
    font-size: 0.9rem;
    color: #333;
    margin-bottom: 0.35rem;
}

.form-group .label-hint {
    font-weight: 400;
    color: #8895a7;
    font-size: 0.82rem;
    margin-left: 0.3rem;
}

.form-group input,
.form-group select {
    width: 100%;
    padding: 0.7rem 0.9rem;
    border: 1.5px solid #d1d9e6;
    border-radius: 8px;
    font-size: 1rem;
    color: #2d2d2d;
    background: #ffffff;
    transition: border-color 0.15s ease;
}

.form-group input:focus,
.form-group select:focus {
    outline: none;
    border-color: #0066cc;
    box-shadow: 0 0 0 3px rgba(0, 102, 204, 0.12);
}

.btn-calculate {
    display: inline-block;
    padding: 0.8rem 2rem;
    background: #0066cc;
    color: #ffffff;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.15s ease;
    margin-top: 0.5rem;
}

.btn-calculate:hover { background: #0052a3; }

/* ===== RESULTS ===== */
.results-section {
    background: #ffffff;
    border: 1px solid #e2e8f0;
    border-radius: 12px;
    padding: 2rem;
    margin-bottom: 1.5rem;
    display: none;
}

.results-section.visible { display: block; }

.results-section h2 {
    font-size: 1.35rem;
    font-weight: 700;
    color: #1a1a2e;
    margin-bottom: 1.25rem;
}

.result-row {
    display: flex;
    justify-content: space-between;
    align-items: baseline;
    padding: 0.6rem 0;
    border-bottom: 1px solid #f0f2f5;
}
.result-row:last-child { border-bottom: none; }

.result-label {
    font-size: 0.95rem;
    color: #555;
}

.result-value {
    font-size: 1.1rem;
    font-weight: 700;
    color: #1a1a2e;
}

.result-value.positive { color: #28a745; }
.result-value.negative { color: #dc3545; }

/* ===== CHART ===== */
.chart-section {
    background: #ffffff;
    border: 1px solid #e2e8f0;
    border-radius: 12px;
    padding: 2rem;
    margin-bottom: 1.5rem;
    display: none;
}
.chart-section.visible { display: block; }

.chart-section h2 {
    font-size: 1.25rem;
    font-weight: 700;
    color: #1a1a2e;
    margin-bottom: 1rem;
}

.chart-container {
    position: relative;
    width: 100%;
    max-height: 400px;
}

/* ===== EDUCATIONAL CONTENT ===== */
.edu-section {
    background: #ffffff;
    border: 1px solid #e2e8f0;
    border-radius: 12px;
    padding: 2rem;
    margin-bottom: 1.5rem;
}

.edu-section h2 {
    font-size: 1.35rem;
    font-weight: 700;
    color: #1a1a2e;
    margin-bottom: 1rem;
}

.edu-section h3 {
    font-size: 1.1rem;
    font-weight: 600;
    color: #333;
    margin: 1.25rem 0 0.5rem;
}

.edu-section p, .edu-section li {
    font-size: 0.95rem;
    color: #444;
    line-height: 1.7;
}

.edu-section ul, .edu-section ol {
    padding-left: 1.5rem;
    margin-bottom: 1rem;
}

.formula-block {
    background: #f0f4f8;
    border: 1px solid #d1d9e6;
    border-radius: 8px;
    padding: 1.25rem 1.5rem;
    font-family: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
    font-size: 0.95rem;
    color: #1a1a2e;
    overflow-x: auto;
    margin: 1rem 0;
    line-height: 1.8;
}

/* ===== AD SLOTS ===== */
.ad-slot {
    background: #f0f2f5;
    border: 1px dashed #ccd6e0;
    border-radius: 8px;
    min-height: 90px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #adb5bd;
    font-size: 0.8rem;
    text-transform: uppercase;
    letter-spacing: 0.06em;
}

.ad-slot[data-ad-slot="top-banner"] { min-height: 90px; margin-bottom: 1.5rem; }
.ad-slot[data-ad-slot="mid-content"] { min-height: 250px; margin: 1.5rem 0; }
.ad-slot[data-ad-slot="sidebar"] { min-height: 600px; }

/* ===== SIDEBAR WIDGETS ===== */
.sidebar-widget {
    background: #ffffff;
    border: 1px solid #e2e8f0;
    border-radius: 12px;
    padding: 1.5rem;
}

.sidebar-widget h3 {
    font-size: 1.05rem;
    font-weight: 700;
    color: #1a1a2e;
    margin-bottom: 1rem;
    padding-bottom: 0.5rem;
    border-bottom: 2px solid #e2e8f0;
}

.sidebar-widget ul { list-style: none; }

.sidebar-widget li {
    padding: 0.5rem 0;
    border-bottom: 1px solid #f0f2f5;
}
.sidebar-widget li:last-child { border-bottom: none; }

.sidebar-widget li a {
    font-size: 0.9rem;
    color: #0066cc;
    display: block;
}

/* ===== FOOTER ===== */
.site-footer {
    background: #1a1a2e;
    color: #8895a7;
    padding: 2.5rem 0;
    margin-top: auto;
    font-size: 0.875rem;
}

.footer-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 2rem;
    margin-bottom: 2rem;
}

.footer-col h4 {
    color: #ffffff;
    font-size: 0.95rem;
    margin-bottom: 0.75rem;
}

.footer-col ul { list-style: none; }
.footer-col li { margin-bottom: 0.4rem; }
.footer-col a { color: #8895a7; }
.footer-col a:hover { color: #ffffff; }

.footer-bottom {
    border-top: 1px solid #2a2a4a;
    padding-top: 1.5rem;
    text-align: center;
    color: #6c757d;
    font-size: 0.8rem;
    line-height: 1.7;
}

/* ===== RESPONSIVE ===== */
@media (max-width: 900px) {
    .calc-layout {
        grid-template-columns: 1fr;
    }
    .calc-sidebar { order: 2; }
    .ad-slot[data-ad-slot="sidebar"] { min-height: 250px; }
}

@media (max-width: 600px) {
    .hero h1 { font-size: 1.8rem; }
    .hero p { font-size: 1rem; }
    .card-grid { grid-template-columns: 1fr; }
    .calc-form-section { padding: 1.25rem; }
    .container { padding: 0 1rem; }
    .site-header .container { flex-direction: column; align-items: flex-start; }
}

/* ===== CATEGORY PAGE ===== */
.category-header {
    padding: 3rem 0 1.5rem;
}

.category-header h1 {
    font-size: 2rem;
    font-weight: 800;
    color: #1a1a2e;
    margin-bottom: 0.5rem;
}

.category-header p {
    color: #555;
    font-size: 1.05rem;
    max-width: 700px;
}

/* ===== POPULAR SECTION ===== */
.popular-section {
    padding: 3rem 0;
}

.categories-section {
    padding: 3rem 0 2rem;
}