/* ==============================================================================
 * Sphere Volume Formula - Master Stylesheet
 * Green Visual Identity System (#087A3D, #075B32, #EAF8F0, #F6FCF8)
 * Clean Semantic Layout, Working Math Components & Responsive UI
 * ============================================================================== */

:root {
    --primary-color: #087A3D;
    --primary-hover: #066733;
    --primary-dark: #075B32;
    --primary-light: #EAF8F0;
    --primary-subtle: #F6FCF8;
    --accent-color: #10b981;

    --bg-color: #F6FCF8;
    --card-bg: #FFFFFF;
    --text-color: #12352A;
    --text-muted: #587067;
    --border-color: #D7EADF;
    --focus-ring: rgba(8, 122, 61, 0.25);

    --success-bg: #EAF8F0;
    --success-text: #087A3D;
    --error-bg: #fee2e2;
    --error-text: #b91c1c;

    --font-main: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    --font-mono: SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;

    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;

    --shadow-sm: 0 1px 3px rgba(8, 122, 61, 0.04);
    --shadow-md: 0 4px 8px -1px rgba(8, 122, 61, 0.08), 0 2px 4px -1px rgba(8, 122, 61, 0.04);
    --shadow-lg: 0 10px 20px -3px rgba(8, 122, 61, 0.1), 0 4px 6px -2px rgba(8, 122, 61, 0.05);
    --shadow-xl: 0 20px 25px -5px rgba(8, 122, 61, 0.1), 0 10px 10px -5px rgba(8, 122, 61, 0.04);
}

[data-theme="dark"] {
    --bg-color: #0d1f18;
    --card-bg: #142a22;
    --text-color: #e6f4ed;
    --text-muted: #9ab4a7;
    --border-color: #214739;
    --focus-ring: rgba(16, 185, 129, 0.35);
    --primary-light: #1b382d;
    --primary-subtle: #0d1f18;
}

/* Global Reset & Base */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-main);
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.65;
    font-size: 16px;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    -webkit-font-smoothing: antialiased;
}

a {
    color: var(--primary-color);
    text-decoration: none;
    transition: color 0.15s ease;
}

a:hover {
    color: var(--primary-hover);
    text-decoration: underline;
}

.container {
    width: 100%;
    max-width: 1240px;
    margin: 0 auto;
    padding: 0 20px;
}

.main-content-wrapper {
    flex: 1;
    padding: 24px 0 60px 0;
}

/* Typography & Headings */
h1, h2, h3, h4, h5, h6 {
    color: var(--primary-dark);
    line-height: 1.3;
    margin-bottom: 0.75rem;
    font-weight: 700;
}

h1 { font-size: 2.4rem; font-weight: 800; letter-spacing: -0.02em; }
h2 { font-size: 1.75rem; font-weight: 700; margin-top: 2rem; }
h3 { font-size: 1.3rem; font-weight: 600; margin-top: 1.5rem; }

p {
    margin-bottom: 1rem;
    color: var(--text-color);
}

.lead-text {
    font-size: 1.125rem;
    color: var(--text-muted);
    line-height: 1.7;
    margin-bottom: 1.5rem;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px 24px;
    font-size: 1rem;
    font-weight: 600;
    border-radius: var(--radius-md);
    border: none;
    cursor: pointer;
    transition: all 0.2s ease;
    text-decoration: none;
    line-height: 1;
}

.btn-primary {
    background-color: var(--primary-color);
    color: #ffffff;
}
.btn-primary:hover {
    background-color: var(--primary-hover);
    box-shadow: var(--shadow-md);
    text-decoration: none;
    color: #ffffff;
}

.btn-dark {
    background-color: var(--primary-dark);
    color: #ffffff;
}
.btn-dark:hover {
    background-color: #054625;
    text-decoration: none;
    color: #ffffff;
}

.btn-white {
    background-color: #ffffff;
    color: var(--primary-dark);
    font-weight: 700;
}
.btn-white:hover {
    background-color: #f1f8f4;
    text-decoration: none;
    color: var(--primary-dark);
}

.btn-outline {
    background-color: #ffffff;
    border: 1px solid var(--border-color);
    color: var(--text-color);
}
.btn-outline:hover {
    background-color: var(--primary-light);
    border-color: var(--primary-color);
    color: var(--primary-color);
    text-decoration: none;
}

.btn-sm {
    padding: 8px 16px;
    font-size: 0.875rem;
    border-radius: var(--radius-sm);
}

.btn-lg {
    padding: 14px 28px;
    font-size: 1.05rem;
    border-radius: var(--radius-md);
}

/* Header & Navigation Bar */
.site-header {
    background-color: #ffffff;
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: var(--shadow-sm);
    transition: box-shadow 0.2s ease;
}

.header-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 70px;
    max-width: 1260px;
    margin: 0 auto;
    padding: 0 20px;
    gap: 16px;
}

.brand-logo {
    display: flex;
    align-items: center;
    gap: 12px;
    text-decoration: none;
    flex-shrink: 0;
}
.brand-logo:hover {
    text-decoration: none;
}

.brand-logo img {
    width: 38px;
    height: 38px;
    border-radius: 50%;
    object-fit: cover;
    border: 1.5px solid var(--border-color);
}

.site-title {
    font-size: 1.15rem;
    font-weight: 800;
    color: var(--primary-dark);
    line-height: 1.2;
    letter-spacing: -0.01em;
}

/* Main Desktop Navigation */
.main-nav {
    display: flex;
    align-items: center;
}

.nav-links {
    display: flex;
    list-style: none;
    gap: 4px;
    align-items: center;
    margin: 0;
    padding: 0;
}

.nav-item {
    position: relative;
}

.nav-item > a,
.nav-item > button.dropdown-toggle {
    display: flex;
    align-items: center;
    gap: 5px;
    padding: 9px 12px;
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-color);
    border-radius: var(--radius-sm);
    background: none;
    border: none;
    cursor: pointer;
    font-family: inherit;
    transition: all 0.15s ease;
    text-decoration: none;
}

.nav-item > a:hover,
.nav-item > button.dropdown-toggle:hover,
.nav-item.active > a {
    color: var(--primary-color);
    background-color: var(--primary-light);
    text-decoration: none;
}

.dropdown-caret {
    transition: transform 0.2s ease;
}

.nav-item.has-dropdown:hover .dropdown-caret,
.nav-item.has-dropdown.open .dropdown-caret {
    transform: rotate(180deg);
}

/* Dropdown Menu Popup (Desktop) */
.dropdown-menu {
    position: absolute;
    top: calc(100% + 4px);
    left: 0;
    min-width: 250px;
    background-color: #ffffff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-xl);
    padding: 8px 0;
    list-style: none;
    opacity: 0;
    visibility: hidden;
    transform: translateY(8px);
    transition: opacity 0.2s ease, transform 0.2s ease, visibility 0.2s;
    z-index: 1050;
}

.dropdown-menu.dropdown-align-right {
    left: auto;
    right: 0;
}

.nav-item.has-dropdown:hover .dropdown-menu,
.nav-item.has-dropdown:focus-within .dropdown-menu {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.dropdown-menu li a {
    display: block;
    padding: 8px 18px;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-color);
    transition: all 0.15s ease;
    text-decoration: none;
}

.dropdown-menu li a:hover {
    background-color: var(--primary-light);
    color: var(--primary-color);
    padding-left: 22px;
    text-decoration: none;
}

.dropdown-menu li.divider {
    height: 1px;
    background-color: var(--border-color);
    margin: 6px 0;
}

/* Header Right: Search Button */
.header-actions {
    display: flex;
    align-items: center;
    gap: 8px;
}

.search-trigger-btn {
    background: none;
    border: none;
    color: var(--text-color);
    width: 36px;
    height: 36px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: background-color 0.15s ease, color 0.15s ease;
}
.search-trigger-btn:hover {
    background-color: var(--primary-light);
    color: var(--primary-color);
}

/* Mobile Hamburger Button */
.mobile-menu-btn {
    display: none;
    flex-direction: column;
    justify-content: space-around;
    width: 38px;
    height: 38px;
    background: #ffffff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    cursor: pointer;
    padding: 8px;
    color: var(--text-color);
}

.mobile-menu-btn span {
    width: 100%;
    height: 2px;
    background-color: var(--text-color);
    border-radius: 2px;
    transition: all 0.25s ease;
}

/* Breadcrumbs */
.breadcrumb-nav {
    margin-bottom: 24px;
}

.breadcrumb-list {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    list-style: none;
    gap: 8px;
    font-size: 0.875rem;
    color: var(--text-muted);
}

.breadcrumb-item a {
    color: var(--text-muted);
}
.breadcrumb-item a:hover {
    color: var(--primary-color);
}

.breadcrumb-separator {
    color: var(--border-color);
    font-size: 0.75rem;
}

.breadcrumb-item.active {
    color: var(--primary-dark);
    font-weight: 600;
}

/* ==============================================================================
 * HOMEPAGE HERO SECTION (2-Column Reference Layout)
 * ============================================================================== */
.hero-wrapper {
    background: #ffffff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 48px 40px;
    margin-bottom: 32px;
    box-shadow: var(--shadow-sm);
}

.hero-grid {
    display: grid;
    grid-template-columns: 1.2fr 0.8fr;
    gap: 40px;
    align-items: center;
}

.hero-content h1 {
    font-size: 3rem;
    font-weight: 800;
    color: var(--primary-dark);
    margin-bottom: 16px;
    line-height: 1.15;
}

.hero-content p {
    font-size: 1.15rem;
    color: var(--text-muted);
    line-height: 1.65;
    margin-bottom: 28px;
    max-width: 580px;
}

.hero-visual {
    display: flex;
    justify-content: center;
    align-items: center;
}

.hero-sphere-svg {
    max-width: 100%;
    height: auto;
    filter: drop-shadow(0 14px 24px rgba(8, 122, 61, 0.15));
}

/* ==============================================================================
 * 4 FEATURE CARDS (Below Hero)
 * ============================================================================== */
.features-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 20px;
    margin-bottom: 40px;
}

.feature-card {
    background: #ffffff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 22px 20px;
    display: flex;
    align-items: center;
    gap: 16px;
    transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
    text-decoration: none;
}

.feature-card:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-md);
    border-color: var(--primary-color);
    text-decoration: none;
}

.feature-icon-box {
    width: 48px;
    height: 48px;
    background: var(--primary-light);
    color: var(--primary-color);
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.feature-card h3 {
    font-size: 1rem;
    font-weight: 700;
    color: var(--primary-dark);
    margin: 0 0 4px 0;
}

.feature-card p {
    font-size: 0.825rem;
    color: var(--text-muted);
    margin: 0;
    line-height: 1.4;
}

/* ==============================================================================
 * HOMEPAGE INFO SECTION ("What is Sphere Volume Formula?")
 * ============================================================================== */
.info-section-grid {
    display: grid;
    grid-template-columns: 1.3fr 0.9fr;
    gap: 28px;
    margin-bottom: 40px;
}

.info-card {
    background: #ffffff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 32px;
}

.info-card h2 {
    font-size: 1.6rem;
    margin-top: 0;
    margin-bottom: 16px;
    color: var(--primary-dark);
}

.info-card p {
    font-size: 1rem;
    color: var(--text-muted);
    line-height: 1.7;
    margin-bottom: 20px;
}

.quick-formula-card {
    background: #ffffff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 28px;
    display: flex;
    flex-direction: column;
    justify-content: center;
}

.quick-formula-card h3 {
    font-size: 1.1rem;
    color: var(--text-muted);
    font-weight: 700;
    margin: 0 0 16px 0;
}

.quick-formula-math {
    font-size: 2.2rem;
    font-weight: 900;
    color: var(--primary-dark);
    font-family: var(--font-mono);
    margin-bottom: 16px;
}

.quick-formula-vars {
    font-size: 0.95rem;
    color: var(--text-muted);
    line-height: 1.8;
}

/* ==============================================================================
 * POPULAR SPHERE CALCULATORS GRID
 * ============================================================================== */
.popular-section {
    margin-bottom: 40px;
}

.section-header-flex {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
}

.section-header-flex h2 {
    margin: 0;
    font-size: 1.5rem;
    color: var(--primary-dark);
}

.popular-cards-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 18px;
}

.popular-calc-card {
    background: #ffffff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 18px 20px;
    display: flex;
    align-items: center;
    gap: 14px;
    text-decoration: none;
    transition: transform 0.2s ease, border-color 0.2s ease, box-shadow 0.2s ease;
}

.popular-calc-card:hover {
    transform: translateY(-2px);
    border-color: var(--primary-color);
    box-shadow: var(--shadow-sm);
    text-decoration: none;
}

.popular-calc-icon {
    width: 36px;
    height: 36px;
    border-radius: 50%;
    background: var(--primary-light);
    color: var(--primary-color);
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.popular-calc-title {
    font-size: 0.95rem;
    font-weight: 700;
    color: var(--text-color);
}

/* ==============================================================================
 * DARK GREEN CTA BANNER ("Master the Sphere Volume Formula")
 * ============================================================================== */
.cta-banner-dark {
    background: linear-gradient(135deg, #075B32 0%, #054625 100%);
    border-radius: var(--radius-lg);
    padding: 40px 48px;
    color: #ffffff;
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 44px;
    position: relative;
    overflow: hidden;
    box-shadow: var(--shadow-md);
}

.cta-banner-content h2 {
    color: #ffffff;
    font-size: 1.85rem;
    margin: 0 0 10px 0;
}

.cta-banner-content p {
    color: rgba(255, 255, 255, 0.85);
    font-size: 1.05rem;
    margin: 0 0 22px 0;
}

.cta-banner-visual {
    opacity: 0.25;
    flex-shrink: 0;
}

/* ==============================================================================
 * DEDICATED 2-COLUMN CALCULATOR LAYOUT
 * ============================================================================== */
.calc-layout-2col {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 28px;
    margin-bottom: 36px;
}

.calc-box-card {
    background: #ffffff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 28px;
    box-shadow: var(--shadow-sm);
}

/* Mode Switch Tabs */
.calc-mode-switch {
    display: flex;
    background: var(--primary-subtle);
    padding: 4px;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    margin-bottom: 22px;
    gap: 4px;
}

.mode-btn {
    flex: 1;
    padding: 10px 16px;
    font-size: 0.95rem;
    font-weight: 700;
    border-radius: var(--radius-sm);
    border: none;
    background: none;
    color: var(--text-muted);
    cursor: pointer;
    transition: all 0.2s ease;
}

.mode-btn.active {
    background: var(--primary-color);
    color: #ffffff;
    box-shadow: var(--shadow-sm);
}

.form-group {
    display: flex;
    flex-direction: column;
    margin-bottom: 18px;
}

.form-label {
    font-weight: 700;
    font-size: 0.95rem;
    margin-bottom: 8px;
    color: var(--text-color);
}

.input-with-unit {
    display: flex;
    align-items: stretch;
}

.form-input {
    flex: 1;
    padding: 12px 16px;
    font-size: 1.05rem;
    font-weight: 600;
    border: 1.5px solid var(--border-color);
    border-radius: var(--radius-md);
    background-color: #ffffff;
    color: var(--text-color);
    outline: none;
    transition: border-color 0.2s ease;
}

.input-with-unit .form-input {
    border-radius: var(--radius-md) 0 0 var(--radius-md);
}

.form-input:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px var(--focus-ring);
}

.unit-select {
    padding: 12px 16px;
    font-size: 0.95rem;
    font-weight: 600;
    border: 1.5px solid var(--border-color);
    border-left: none;
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
    background-color: var(--primary-subtle);
    color: var(--text-color);
    cursor: pointer;
    outline: none;
}

.unit-select:focus {
    border-color: var(--primary-color);
}

.form-help {
    font-size: 0.8rem;
    color: var(--text-muted);
    margin-top: 6px;
}

.calc-actions {
    display: flex;
    gap: 12px;
    margin-top: 14px;
}

/* Result Card on Right */
.calc-result-box {
    background: #ffffff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 28px;
    box-shadow: var(--shadow-sm);
    display: flex;
    flex-direction: column;
}

.calc-result-badge {
    font-size: 0.85rem;
    font-weight: 700;
    text-transform: uppercase;
    color: var(--text-muted);
    margin-bottom: 6px;
}

.calc-result-number {
    font-size: 2.4rem;
    font-weight: 900;
    color: var(--primary-dark);
    font-family: var(--font-mono);
    margin-bottom: 16px;
}

.calc-steps-card {
    background: var(--primary-subtle);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 18px;
    margin-top: 18px;
    flex: 1;
}

.calc-steps-title {
    font-size: 0.95rem;
    font-weight: 700;
    color: var(--primary-dark);
    margin-bottom: 10px;
}

.step-item {
    padding: 6px 0;
    border-bottom: 1px dashed var(--border-color);
    font-size: 0.9rem;
    color: var(--text-color);
}

.step-item:last-child {
    border-bottom: none;
    font-weight: 700;
    color: var(--primary-dark);
}

/* Formula & Example 2-col below calculator */
.calc-supporting-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 28px;
    margin-bottom: 36px;
}

.supporting-card {
    background: #ffffff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 26px;
}

.supporting-card h3 {
    font-size: 1.15rem;
    margin-top: 0;
    margin-bottom: 14px;
    color: var(--primary-dark);
}

/* Worked Examples with View Steps Toggle */
.example-box {
    background: #ffffff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 24px;
    margin-bottom: 20px;
}

.example-box h3 {
    margin-top: 0;
    font-size: 1.2rem;
    color: var(--primary-dark);
    display: flex;
    align-items: center;
    gap: 10px;
}

.example-math-highlight {
    font-family: var(--font-mono);
    font-size: 1.15rem;
    font-weight: 700;
    color: var(--primary-dark);
    margin: 12px 0;
}

.example-steps-drawer {
    display: none;
    background: var(--primary-subtle);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 16px 20px;
    margin-top: 14px;
}

.example-steps-drawer.open {
    display: block;
    animation: fadeIn 0.2s ease;
}

/* ==============================================================================
 * BLOG LISTING & ARTICLE STYLES
 * ============================================================================== */
.blog-categories-bar {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
    margin-bottom: 28px;
}

.category-pill {
    display: inline-flex;
    padding: 6px 16px;
    font-size: 0.85rem;
    font-weight: 700;
    border-radius: 20px;
    background: #ffffff;
    border: 1px solid var(--border-color);
    color: var(--text-color);
    text-decoration: none;
    transition: all 0.15s ease;
}

.category-pill:hover, .category-pill.active {
    background: var(--primary-color);
    border-color: var(--primary-color);
    color: #ffffff;
    text-decoration: none;
}

.blog-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 24px;
    margin-bottom: 40px;
}

.blog-card {
    background: #ffffff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    overflow: hidden;
    display: flex;
    flex-direction: column;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
    text-decoration: none;
}

.blog-card:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-md);
    text-decoration: none;
}

.blog-card-thumb {
    width: 100%;
    height: 180px;
    background: var(--primary-light);
    display: flex;
    align-items: center;
    justify-content: center;
}

.blog-card-body {
    padding: 22px;
    display: flex;
    flex-direction: column;
    flex: 1;
}

.blog-badge {
    align-self: flex-start;
    background: var(--primary-light);
    color: var(--primary-color);
    font-size: 0.75rem;
    font-weight: 700;
    padding: 3px 10px;
    border-radius: 4px;
    margin-bottom: 12px;
}

.blog-card h3 {
    font-size: 1.15rem;
    font-weight: 700;
    color: var(--primary-dark);
    margin: 0 0 10px 0;
    line-height: 1.35;
}

.blog-card p {
    font-size: 0.875rem;
    color: var(--text-muted);
    line-height: 1.5;
    margin-bottom: 16px;
    flex: 1;
}

.blog-meta {
    display: flex;
    justify-content: space-between;
    font-size: 0.8rem;
    color: var(--text-muted);
    border-top: 1px solid var(--border-color);
    padding-top: 12px;
}

/* ==============================================================================
 * ABOUT PAGE STATS & CHECKMARKS
 * ============================================================================== */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 24px;
    margin: 36px 0;
}

.stat-box {
    background: #ffffff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 32px 24px;
    text-align: center;
    box-shadow: var(--shadow-sm);
}

.stat-number {
    font-size: 2.8rem;
    font-weight: 900;
    color: var(--primary-color);
    line-height: 1;
    margin-bottom: 8px;
    font-family: var(--font-mono);
}

.stat-label {
    font-size: 1rem;
    font-weight: 700;
    color: var(--text-muted);
}

.checkmark-list {
    list-style: none;
    padding: 0;
    margin: 20px 0;
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.checkmark-item {
    display: flex;
    align-items: center;
    gap: 12px;
    font-size: 1.05rem;
    color: var(--text-color);
}

.check-icon {
    width: 24px;
    height: 24px;
    border-radius: 50%;
    background: var(--primary-light);
    color: var(--primary-color);
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    font-weight: bold;
}

/* ==============================================================================
 * FAQ ACCORDION
 * ============================================================================== */
.faq-list {
    display: flex;
    flex-direction: column;
    gap: 12px;
    margin-top: 20px;
}

.faq-item {
    background-color: #ffffff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    overflow: hidden;
    transition: border-color 0.15s ease;
}

.faq-item.active {
    border-color: var(--primary-color);
}

.faq-question {
    padding: 18px 22px;
    font-weight: 700;
    font-size: 1.05rem;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    user-select: none;
    color: var(--primary-dark);
}

.faq-chevron {
    transition: transform 0.2s ease;
    color: var(--text-muted);
}

.faq-item.active .faq-chevron {
    transform: rotate(180deg);
    color: var(--primary-color);
}

.faq-answer {
    padding: 0 22px 20px 22px;
    color: var(--text-color);
    font-size: 0.95rem;
    line-height: 1.65;
    display: none;
}

.faq-item.active .faq-answer {
    display: block;
    animation: fadeIn 0.2s ease;
}

/* ==============================================================================
 * FOOTER
 * ============================================================================== */
.site-footer {
    background-color: #ffffff;
    border-top: 1px solid var(--border-color);
    padding: 56px 0 28px 0;
    margin-top: auto;
}

.footer-grid {
    display: grid;
    grid-template-columns: 1.4fr 1fr 1fr 1fr;
    gap: 36px;
    margin-bottom: 40px;
}

.footer-brand {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 14px;
}

.footer-title {
    font-weight: 800;
    font-size: 1.15rem;
    color: var(--primary-dark);
}

.footer-desc {
    font-size: 0.875rem;
    color: var(--text-muted);
    line-height: 1.65;
    margin-bottom: 16px;
}

.footer-heading {
    font-size: 0.95rem;
    font-weight: 800;
    color: var(--primary-dark);
    margin-bottom: 16px;
}

.footer-col ul {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 10px;
    padding: 0;
    margin: 0;
}

.footer-col a {
    font-size: 0.875rem;
    color: var(--text-muted);
    text-decoration: none;
    transition: color 0.15s ease;
}

.footer-col a:hover {
    color: var(--primary-color);
    text-decoration: underline;
}

.footer-bottom {
    padding-top: 24px;
    border-top: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 16px;
    font-size: 0.85rem;
    color: var(--text-muted);
}

/* ==============================================================================
 * SEARCH MODAL OVERLAY
 * ============================================================================== */
.search-modal-backdrop {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(18, 53, 42, 0.4);
    backdrop-filter: blur(4px);
    z-index: 2000;
    align-items: flex-start;
    justify-content: center;
    padding: 80px 20px 20px 20px;
}

.search-modal-backdrop.active {
    display: flex;
    animation: fadeIn 0.2s ease;
}

.search-modal-box {
    background: #ffffff;
    width: 100%;
    max-width: 600px;
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-xl);
    overflow: hidden;
}

.search-input-wrapper {
    display: flex;
    align-items: center;
    padding: 16px 20px;
    border-bottom: 1px solid var(--border-color);
    gap: 12px;
}

.search-input-field {
    flex: 1;
    border: none;
    outline: none;
    font-size: 1.1rem;
    font-family: inherit;
    color: var(--text-color);
}

.search-close-btn {
    background: none;
    border: none;
    font-size: 1.25rem;
    cursor: pointer;
    color: var(--text-muted);
}

.search-results-list {
    max-height: 380px;
    overflow-y: auto;
    padding: 10px;
}

.search-result-item {
    padding: 12px 16px;
    border-radius: var(--radius-sm);
    display: block;
    text-decoration: none;
    transition: background 0.15s ease;
}

.search-result-item:hover {
    background: var(--primary-light);
    text-decoration: none;
}

.search-result-title {
    font-weight: 700;
    color: var(--primary-dark);
    font-size: 0.95rem;
}

.search-result-desc {
    font-size: 0.825rem;
    color: var(--text-muted);
    margin-top: 2px;
}

.search-result-badge {
    display: inline-block;
    font-size: 0.7rem;
    font-weight: 700;
    background: var(--primary-light);
    color: var(--primary-color);
    padding: 2px 6px;
    border-radius: 4px;
    margin-bottom: 4px;
}

/* Animations */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(6px); }
    to { opacity: 1; transform: translateY(0); }
}

/* ==============================================================================
 * RESPONSIVE BREAKPOINTS
 * ============================================================================== */
@media (max-width: 1024px) {
    .hero-grid {
        grid-template-columns: 1fr;
        text-align: center;
    }
    .hero-content p {
        margin-left: auto;
        margin-right: auto;
    }
    .hero-visual {
        max-width: 320px;
        margin: 0 auto;
    }
    .features-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    .popular-cards-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    .calc-layout-2col, .calc-supporting-grid, .info-section-grid {
        grid-template-columns: 1fr;
    }
    .blog-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    .footer-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 900px) {
    .mobile-menu-btn {
        display: flex;
    }
    .main-nav {
        display: none;
        position: absolute;
        top: 70px;
        left: 0;
        right: 0;
        background: #ffffff;
        border-bottom: 2px solid var(--border-color);
        box-shadow: var(--shadow-xl);
        padding: 16px 20px;
        max-height: 85vh;
        overflow-y: auto;
    }
    .main-nav.active {
        display: block;
        animation: fadeIn 0.2s ease;
    }
    .nav-links {
        flex-direction: column;
        align-items: stretch;
        gap: 4px;
    }
    .nav-item > a, .nav-item > button.dropdown-toggle {
        width: 100%;
        justify-content: space-between;
        padding: 12px 14px;
        font-size: 0.95rem;
    }
    .dropdown-menu {
        position: static;
        box-shadow: none;
        border: none;
        border-left: 3px solid var(--primary-color);
        border-radius: 0;
        margin-left: 12px;
        margin-top: 4px;
        margin-bottom: 8px;
        display: none;
        opacity: 1;
        visibility: visible;
        transform: none;
        padding: 4px 0;
        background-color: var(--primary-subtle);
    }
    .nav-item.has-dropdown.open .dropdown-menu {
        display: block;
    }
    .dropdown-menu li a {
        padding: 8px 16px;
    }
}

@media (max-width: 640px) {
    .hero-wrapper {
        padding: 32px 20px;
    }
    .hero-content h1 {
        font-size: 2.2rem;
    }
    .features-grid {
        grid-template-columns: 1fr;
    }
    .popular-cards-grid {
        grid-template-columns: 1fr;
    }
    .blog-grid {
        grid-template-columns: 1fr;
    }
    .stats-grid {
        grid-template-columns: 1fr;
    }
    .cta-banner-dark {
        padding: 30px 24px;
        flex-direction: column;
        text-align: center;
        gap: 20px;
    }
    .footer-grid {
        grid-template-columns: 1fr;
    }
}