/**
 * Kintail Lesson Styles
 * Shared CSS for all lesson pages (A2 and B1)
 * 
 * This file replaces ~1400 lines of inline CSS that was duplicated
 * across 42 lesson files (~58,000 total lines eliminated)
 */

/* ============================================
   CSS RESET & VARIABLES
   ============================================ */

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

:root {
    /* Kintail Brand Colors */
    --brand-orange: #ea6b3c;
    --brand-dark-blue: #496986;
    --brand-medium-blue: #567d9e;
    --brand-light-blue: #cad8e4;
    --brand-pale-bg: #e7ecf0;
    --brand-text-color: #496986;
    --brand-accent-orange: #ed6a2c;

    /* Extended palette */
    --brand-orange-light: #fdf0eb;
    --brand-orange-soft: #f8d4c7;
    --brand-blue-soft: #f0f4f7;
    --brand-white: #ffffff;
    --brand-dark: #2d4255;

    /* Theme Variables */
    --bg-primary: var(--brand-pale-bg);
    --bg-card: var(--brand-white);
    --text-primary: var(--brand-dark-blue);
    --text-secondary: var(--brand-medium-blue);
    --text-muted: #7a9ab5;
    --accent: var(--brand-orange);
    --glass-bg: rgba(255,255,255,0.85);
    --glass-border: rgba(73,105,134,0.12);
    --card-shadow: 0 4px 20px rgba(73,105,134,0.1);

    /* Status Colors */
    --success: #10b981;
    --success-light: #d1fae5;
    --error: #ef4444;
    --error-light: #fee2e2;
    --warning: #f59e0b;
    --warning-light: #fef3c7;

    /* Typography */
    --font-heading: 'Quicksand', sans-serif;
    --font-body: 'Nunito', sans-serif;
}

/* ============================================
   BASE STYLES
   ============================================ */

body {
    font-family: var(--font-body);
    background: var(--bg-primary);
    color: var(--text-primary);
    min-height: 100vh;
    line-height: 1.6;
    overflow-x: hidden;
}

/* ============================================
   DECORATIVE BACKGROUND
   ============================================ */

.bg-decoration {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 0;
    pointer-events: none;
    overflow: hidden;
}

.blob {
    position: absolute;
    border-radius: 50%;
    filter: blur(60px);
    opacity: 0.4;
}

.blob-1 {
    width: 350px;
    height: 350px;
    background: var(--brand-light-blue);
    top: -80px;
    right: -80px;
    animation: float1 20s ease-in-out infinite;
}

.blob-2 {
    width: 250px;
    height: 250px;
    background: var(--brand-orange-light);
    bottom: 20%;
    left: -80px;
    animation: float2 25s ease-in-out infinite;
}

.blob-3 {
    width: 200px;
    height: 200px;
    background: var(--brand-light-blue);
    top: 50%;
    right: 5%;
    animation: float3 18s ease-in-out infinite;
}

@keyframes float1 { 0%,100%{transform:translate(0,0)} 50%{transform:translate(-30px,30px)} }
@keyframes float2 { 0%,100%{transform:translate(0,0)} 50%{transform:translate(40px,-20px)} }
@keyframes float3 { 0%,100%{transform:translate(0,0)} 50%{transform:translate(-20px,40px)} }

.page-container { position: relative; z-index: 1; }

/* ============================================
   HEADER (Generic)
   ============================================ */

.header {
    background: var(--glass-bg);
    border-bottom: 1px solid var(--glass-border);
    backdrop-filter: blur(20px);
    padding: 12px 24px;
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-content {
    max-width: 1400px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 15px;
}

.header-left { display: flex; align-items: center; gap: 12px; }

.logo { width: 40px; height: 40px; border-radius: 10px; overflow: hidden; }
.logo img { width: 100%; height: 100%; object-fit: contain; }

.brand h1 {
    font-size: 1.1em;
    font-weight: 700;
    font-family: var(--font-heading);
    color: var(--brand-dark-blue);
}

.brand span {
    font-size: 0.7em;
    font-weight: 600;
    font-style: italic;
    color: var(--brand-orange);
}

.header-nav { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; }

.nav-btn {
    padding: 8px 16px;
    background: var(--bg-card);
    border: 1px solid var(--glass-border);
    border-radius: 20px;
    color: var(--text-secondary);
    font-size: 0.85em;
    font-weight: 600;
    text-decoration: none;
    transition: all 0.3s;
    display: flex;
    align-items: center;
    gap: 6px;
}

.nav-btn:hover {
    background: var(--brand-orange);
    border-color: var(--brand-orange);
    color: white;
}

.nav-btn.primary {
    background: var(--brand-orange);
    border-color: var(--brand-orange);
    color: white;
}

/* ============================================
   LESSON HEADER - Premium Design
   ============================================ */

.lesson-header {
    background: linear-gradient(135deg, 
        rgba(255, 255, 255, 0.95) 0%, 
        rgba(248, 250, 252, 0.98) 100%);
    backdrop-filter: blur(20px);
    border-bottom: 1px solid rgba(73, 105, 134, 0.1);
    padding: 0;
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: 
        0 4px 20px rgba(73, 105, 134, 0.08),
        0 1px 3px rgba(0, 0, 0, 0.04);
}

.lesson-header .header-content {
    max-width: 1400px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 16px 32px;
    gap: 24px;
}

.lesson-header .header-left {
    display: flex;
    align-items: center;
    gap: 28px;
}

/* Back Button - Minimal & Elegant */
.lesson-header .back-btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 10px 18px;
    background: transparent;
    border: 2px solid var(--brand-light-blue);
    border-radius: 12px;
    color: var(--brand-medium-blue);
    font-size: 0.9em;
    font-weight: 600;
    text-decoration: none;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    position: relative;
    overflow: hidden;
}

.lesson-header .back-btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(234, 107, 60, 0.1), transparent);
    transition: left 0.5s;
}

.lesson-header .back-btn:hover {
    border-color: var(--brand-orange);
    color: var(--brand-orange);
    transform: translateX(-4px);
}

.lesson-header .back-btn:hover::before {
    left: 100%;
}

.lesson-header .back-btn span {
    font-size: 1.2em;
    transition: transform 0.3s;
}

.lesson-header .back-btn:hover span {
    transform: translateX(-3px);
}

/* Lesson Badge - The Hero Element */
.lesson-header .lesson-badge {
    display: flex;
    align-items: center;
    gap: 0;
    background: linear-gradient(145deg, #ffffff, #fafbfc);
    border: 2px solid rgba(73, 105, 134, 0.12);
    border-radius: 20px;
    padding: 0;
    overflow: hidden;
    box-shadow: 
        0 8px 32px rgba(73, 105, 134, 0.12),
        0 2px 8px rgba(0, 0, 0, 0.04),
        inset 0 1px 0 rgba(255, 255, 255, 0.8);
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

.lesson-header .lesson-badge:hover {
    transform: translateY(-2px);
    box-shadow: 
        0 12px 40px rgba(73, 105, 134, 0.16),
        0 4px 12px rgba(0, 0, 0, 0.06),
        inset 0 1px 0 rgba(255, 255, 255, 0.9);
    border-color: rgba(234, 107, 60, 0.3);
}

/* Lesson Number - Bold Accent */
.lesson-header .lesson-number {
    background: linear-gradient(145deg, var(--brand-orange), #d4582e);
    color: white;
    font-family: var(--font-heading);
    font-size: 1.4em;
    font-weight: 800;
    padding: 18px 22px;
    min-width: 70px;
    text-align: center;
    letter-spacing: -0.02em;
    position: relative;
}

.lesson-header .lesson-number::after {
    content: '';
    position: absolute;
    right: -12px;
    top: 0;
    bottom: 0;
    width: 24px;
    background: linear-gradient(145deg, var(--brand-orange), #d4582e);
    clip-path: polygon(0 0, 100% 50%, 0 100%);
}

/* Lesson Info */
.lesson-header .lesson-info {
    padding: 14px 28px 14px 24px;
}

.lesson-header .lesson-info h1 {
    font-family: var(--font-heading);
    font-size: 1.35em;
    font-weight: 700;
    color: var(--brand-dark-blue);
    margin: 0 0 4px 0;
    letter-spacing: -0.01em;
    line-height: 1.2;
}

.lesson-header .lesson-info span {
    display: block;
    font-size: 0.85em;
    font-weight: 600;
    color: var(--brand-orange);
    opacity: 0.9;
    letter-spacing: 0.02em;
}

/* Header Meta - Duration & Level */
.lesson-header .header-meta {
    display: flex;
    align-items: center;
    gap: 12px;
}

.lesson-header .meta-item {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 10px 18px;
    background: linear-gradient(135deg, var(--brand-blue-soft), #e8f0f6);
    border: 1px solid rgba(73, 105, 134, 0.12);
    border-radius: 12px;
    font-size: 0.9em;
    font-weight: 700;
    color: var(--brand-dark-blue);
    transition: all 0.3s;
}

.lesson-header .meta-item:hover {
    background: linear-gradient(135deg, var(--brand-orange-light), #fde8df);
    border-color: rgba(234, 107, 60, 0.2);
    transform: translateY(-2px);
}

.lesson-header .meta-item span {
    font-size: 1.1em;
}

/* Responsive Lesson Header */
@media (max-width: 900px) {
    .lesson-header .header-content {
        flex-direction: column;
        padding: 16px 20px;
        gap: 16px;
    }
    
    .lesson-header .header-left {
        flex-direction: column;
        gap: 16px;
        width: 100%;
    }
    
    .lesson-header .back-btn {
        align-self: flex-start;
    }
    
    .lesson-header .lesson-badge {
        width: 100%;
        justify-content: flex-start;
    }
    
    .lesson-header .header-meta {
        width: 100%;
        justify-content: center;
    }
}

@media (max-width: 500px) {
    .lesson-header .lesson-number {
        font-size: 1.1em;
        padding: 14px 16px;
        min-width: 56px;
    }
    
    .lesson-header .lesson-number::after {
        right: -8px;
        width: 16px;
    }
    
    .lesson-header .lesson-info {
        padding: 12px 16px 12px 14px;
    }
    
    .lesson-header .lesson-info h1 {
        font-size: 1.1em;
    }
    
    .lesson-header .meta-item {
        padding: 8px 14px;
        font-size: 0.85em;
    }
}

/* ============================================
   MAIN LAYOUT (Sidebar + Content)
   ============================================ */

.main-layout {
    display: grid;
    grid-template-columns: 280px 1fr;
    max-width: 1400px;
    margin: 0 auto;
    gap: 30px;
    padding: 30px 24px;
    min-height: calc(100vh - 70px);
}

/* ============================================
   SIDEBAR
   ============================================ */

.sidebar {
    position: sticky;
    top: 90px;
    height: fit-content;
    max-height: calc(100vh - 120px);
    overflow-y: auto;
}

.sidebar-card {
    background: var(--bg-card);
    border: 2px solid var(--glass-border);
    border-radius: 20px;
    padding: 24px;
    box-shadow: var(--card-shadow);
}

.lesson-badge {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 6px 14px;
    background: var(--brand-orange-light);
    border: 1px solid var(--brand-orange-soft);
    border-radius: 20px;
    font-size: 0.8em;
    font-weight: 700;
    color: var(--brand-orange);
    margin-bottom: 16px;
}

.sidebar-title {
    font-family: var(--font-heading);
    font-size: 1.3em;
    font-weight: 700;
    color: var(--brand-dark-blue);
    margin-bottom: 8px;
    line-height: 1.3;
}

.sidebar-subtitle {
    font-size: 0.9em;
    color: var(--text-muted);
    margin-bottom: 20px;
    line-height: 1.5;
}

.lesson-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 20px;
}

.meta-tag {
    display: flex;
    align-items: center;
    gap: 5px;
    padding: 6px 12px;
    background: var(--brand-blue-soft);
    border-radius: 15px;
    font-size: 0.8em;
    font-weight: 600;
    color: var(--brand-dark-blue);
}

/* ============================================
   PROGRESS RING
   ============================================ */

.progress-section {
    background: var(--brand-blue-soft);
    border-radius: 16px;
    padding: 20px;
    text-align: center;
    margin-bottom: 20px;
}

.progress-ring-container {
    position: relative;
    width: 100px;
    height: 100px;
    margin: 0 auto 12px;
}

.progress-ring {
    transform: rotate(-90deg);
}

.progress-ring-bg {
    fill: none;
    stroke: var(--brand-light-blue);
    stroke-width: 8;
}

.progress-ring-fill {
    fill: none;
    stroke: var(--brand-orange);
    stroke-width: 8;
    stroke-linecap: round;
    stroke-dasharray: 251;
    stroke-dashoffset: 251;
    transition: stroke-dashoffset 0.8s ease;
}

.progress-text {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-family: var(--font-heading);
    font-size: 1.5em;
    font-weight: 700;
    color: var(--brand-dark-blue);
}

.progress-label {
    font-size: 0.85em;
    color: var(--text-muted);
    font-weight: 600;
}

/* ============================================
   SECTION NAVIGATION
   ============================================ */

.section-nav {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.section-nav-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 14px;
    background: transparent;
    border: none;
    border-radius: 12px;
    cursor: pointer;
    transition: all 0.3s;
    text-align: left;
    font-family: var(--font-body);
}

.section-nav-item:hover {
    background: var(--brand-blue-soft);
}

.section-nav-item.active {
    background: var(--brand-orange-light);
    border: 1px solid var(--brand-orange-soft);
}

.section-nav-item.completed .nav-step {
    background: var(--success);
    color: white;
}

.nav-step {
    width: 28px;
    height: 28px;
    border-radius: 50%;
    background: var(--brand-light-blue);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75em;
    font-weight: 700;
    color: var(--brand-dark-blue);
    flex-shrink: 0;
    transition: all 0.3s;
}

.section-nav-item.active .nav-step {
    background: var(--brand-orange);
    color: white;
}

.nav-label {
    font-size: 0.85em;
    font-weight: 600;
    color: var(--text-secondary);
    line-height: 1.3;
}

.section-nav-item.active .nav-label {
    color: var(--brand-orange);
}

.section-nav-item.completed .nav-label {
    color: var(--success);
}

/* ============================================
   MAIN CONTENT AREA
   ============================================ */

.main-content {
    display: flex;
    flex-direction: column;
    gap: 24px;
}

/* ============================================
   CONTENT SECTIONS
   ============================================ */

.content-section {
    background: var(--bg-card);
    border: 2px solid var(--glass-border);
    border-radius: 24px;
    padding: 32px;
    box-shadow: var(--card-shadow);
    display: none;
    animation: fadeIn 0.4s ease;
}

.content-section.active {
    display: block;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

/* Section card - inner wrapper (compatibility with older lessons) */
.section-card {
    /* Inherits from parent content-section, this is for structure */
}

.section-header {
    display: flex;
    align-items: center;
    gap: 16px;
    margin-bottom: 24px;
    padding-bottom: 20px;
    border-bottom: 2px solid var(--glass-border);
}

.section-icon,
.section-title-icon {
    width: 50px;
    height: 50px;
    border-radius: 14px;
    background: linear-gradient(135deg, var(--brand-orange), var(--brand-accent-orange));
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5em;
    box-shadow: 0 6px 20px rgba(234,107,60,0.3);
}

.section-title-group { flex: 1; }

.section-title {
    font-family: var(--font-heading);
    font-size: 1.5em;
    font-weight: 700;
    color: var(--brand-dark-blue);
    margin-bottom: 4px;
    display: flex;
    align-items: center;
    gap: 14px;
}

.section-subtitle {
    font-size: 0.95em;
    color: var(--text-muted);
    margin-bottom: 24px;
    line-height: 1.5;
}

.section-duration {
    font-size: 0.85em;
    color: var(--text-muted);
    font-weight: 500;
}

/* ============================================
   LEARNING OBJECTIVES
   ============================================ */

.objectives-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 16px;
    margin-bottom: 24px;
}

.objective-card {
    display: flex;
    align-items: flex-start;
    gap: 12px;
    padding: 16px;
    background: var(--brand-blue-soft);
    border-radius: 14px;
    transition: all 0.3s;
}

.objective-card:hover {
    background: var(--brand-orange-light);
    transform: translateX(4px);
}

.objective-check {
    width: 24px;
    height: 24px;
    border-radius: 50%;
    background: var(--success);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 0.8em;
    flex-shrink: 0;
}

.objective-text {
    font-size: 0.95em;
    color: var(--text-primary);
    line-height: 1.5;
}

/* ============================================
   GRAMMAR CARDS
   ============================================ */

.grammar-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 20px;
}

.grammar-card {
    background: var(--brand-blue-soft);
    border: 2px solid var(--glass-border);
    border-radius: 18px;
    padding: 24px;
    transition: all 0.3s;
}

.grammar-card:hover {
    border-color: var(--brand-medium-blue);
    transform: translateY(-4px);
    box-shadow: 0 12px 30px rgba(73,105,134,0.15);
}

.grammar-card-header {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 16px;
}

.grammar-badge {
    padding: 6px 14px;
    border-radius: 20px;
    font-size: 0.8em;
    font-weight: 700;
}

.badge-simple {
    background: var(--brand-orange-light);
    color: var(--brand-orange);
}

.badge-continuous {
    background: rgba(16,185,129,0.15);
    color: var(--success);
}

.grammar-card h4 {
    font-family: var(--font-heading);
    font-size: 1.15em;
    font-weight: 700;
    color: var(--brand-dark-blue);
    margin-bottom: 12px;
}

.grammar-formula {
    background: var(--bg-card);
    border: 2px dashed var(--brand-medium-blue);
    border-radius: 10px;
    padding: 12px 16px;
    font-family: 'Courier New', monospace;
    font-size: 0.9em;
    color: var(--brand-dark-blue);
    margin-bottom: 14px;
}

.grammar-use {
    font-size: 0.9em;
    color: var(--text-secondary);
    margin-bottom: 12px;
    line-height: 1.6;
}

.time-words {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.time-word {
    padding: 5px 12px;
    background: var(--bg-card);
    border-radius: 15px;
    font-size: 0.8em;
    font-weight: 600;
    color: var(--brand-dark-blue);
}

/* ============================================
   KEY TIP BOX
   ============================================ */

.key-tip {
    background: linear-gradient(135deg, var(--brand-orange-light), #fff5f0);
    border: 2px solid var(--brand-orange-soft);
    border-radius: 16px;
    padding: 20px 24px;
    margin-top: 24px;
    display: flex;
    align-items: flex-start;
    gap: 14px;
}

.tip-icon {
    width: 40px;
    height: 40px;
    border-radius: 12px;
    background: var(--brand-orange);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2em;
    flex-shrink: 0;
}

.tip-content {
    flex: 1;
}

.tip-title {
    font-family: var(--font-heading);
    font-weight: 700;
    color: var(--brand-orange);
    margin-bottom: 4px;
}

.tip-text {
    font-size: 0.95em;
    color: var(--brand-dark-blue);
    line-height: 1.5;
}

/* ============================================
   CONTEXT CARDS
   ============================================ */

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

.context-card {
    background: var(--bg-card);
    border: 2px solid var(--glass-border);
    border-radius: 18px;
    padding: 24px;
    transition: all 0.3s;
}

.context-card:hover {
    border-color: var(--brand-orange);
    box-shadow: 0 8px 25px rgba(73,105,134,0.12);
}

.context-title {
    font-family: var(--font-heading);
    font-size: 1.1em;
    font-weight: 700;
    color: var(--brand-dark-blue);
    margin-bottom: 16px;
    padding-bottom: 12px;
    border-bottom: 2px solid var(--glass-border);
}

.context-item {
    display: flex;
    align-items: flex-start;
    gap: 10px;
    margin-bottom: 12px;
    padding: 10px;
    background: var(--brand-blue-soft);
    border-radius: 10px;
}

.context-emoji {
    font-size: 1.2em;
    flex-shrink: 0;
}

.context-text {
    font-size: 0.9em;
    color: var(--text-primary);
}

.context-text strong {
    color: var(--brand-dark-blue);
}

.context-text em {
    color: var(--brand-orange);
    font-style: normal;
    font-weight: 600;
}

/* ============================================
   EXAMPLES SECTION
   ============================================ */

.examples-container {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.example-card {
    border-radius: 16px;
    padding: 24px;
    border-left: 5px solid;
}

.example-card.positive {
    background: linear-gradient(135deg, var(--success-light), #ecfdf5);
    border-color: var(--success);
}

.example-card.negative {
    background: linear-gradient(135deg, var(--error-light), #fef2f2);
    border-color: var(--error);
}

.example-header {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 16px;
}

.example-icon {
    width: 36px;
    height: 36px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2em;
    font-weight: 700;
}

.example-card.positive .example-icon {
    background: var(--success);
    color: white;
}

.example-card.negative .example-icon {
    background: var(--error);
    color: white;
}

.example-title {
    font-family: var(--font-heading);
    font-weight: 700;
}

.example-card.positive .example-title { color: var(--success); }
.example-card.negative .example-title { color: var(--error); }

.example-list {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.example-item {
    display: flex;
    gap: 12px;
    padding: 14px;
    background: rgba(255,255,255,0.7);
    border-radius: 10px;
}

.example-mark {
    font-weight: 700;
    font-size: 1.1em;
}

.example-card.positive .example-mark { color: var(--success); }
.example-card.negative .example-mark { color: var(--error); }

.example-text {
    font-size: 0.95em;
    color: var(--text-primary);
}

.example-explanation {
    font-size: 0.85em;
    color: var(--text-muted);
    margin-top: 4px;
}

/* ============================================
   AUDIO SECTION - Premium Audio Player
   ============================================ */

/* Support both class names for compatibility */
.audio-section,
.audio-player-card {
    background: linear-gradient(145deg, #1a365d 0%, #2c5282 50%, #2b6cb0 100%);
    border-radius: 24px;
    padding: 32px;
    margin-bottom: 28px;
    position: relative;
    overflow: hidden;
    box-shadow: 
        0 20px 40px rgba(26, 54, 93, 0.3),
        0 0 0 1px rgba(255,255,255,0.1) inset;
}

/* Subtle animated gradient overlay */
.audio-section::before,
.audio-player-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: 
        radial-gradient(ellipse at 20% 20%, rgba(99, 179, 237, 0.15) 0%, transparent 50%),
        radial-gradient(ellipse at 80% 80%, rgba(237, 137, 54, 0.1) 0%, transparent 50%);
    pointer-events: none;
}

.audio-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 24px;
    color: white;
    position: relative;
    z-index: 1;
}

.audio-title {
    display: flex;
    align-items: center;
    gap: 12px;
    font-weight: 700;
    font-size: 1.1em;
    font-family: var(--font-heading);
    letter-spacing: 0.02em;
}

.audio-title span:first-child {
    font-size: 1.4em;
    filter: drop-shadow(0 2px 4px rgba(0,0,0,0.3));
}

.audio-status {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 8px 16px;
    background: rgba(255,255,255,0.12);
    backdrop-filter: blur(10px);
    border-radius: 24px;
    font-size: 0.85em;
    font-weight: 600;
    border: 1px solid rgba(255,255,255,0.15);
}

.status-dot {
    width: 10px;
    height: 10px;
    border-radius: 50%;
    background: #68d391;
    box-shadow: 0 0 12px rgba(104, 211, 145, 0.6);
    animation: pulse-glow 2s ease-in-out infinite;
}

@keyframes pulse-glow {
    0%, 100% { 
        opacity: 1; 
        box-shadow: 0 0 12px rgba(104, 211, 145, 0.6);
    }
    50% { 
        opacity: 0.7; 
        box-shadow: 0 0 20px rgba(104, 211, 145, 0.8);
    }
}

.audio-controls {
    display: flex;
    align-items: center;
    gap: 20px;
    margin-bottom: 20px;
    position: relative;
    z-index: 1;
}

.play-btn {
    width: 64px;
    height: 64px;
    border-radius: 50%;
    background: linear-gradient(145deg, #ffffff, #f0f0f0);
    border: none;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    flex-shrink: 0;
    box-shadow: 
        0 8px 24px rgba(0,0,0,0.25),
        0 0 0 4px rgba(255,255,255,0.1);
}

.play-btn:hover {
    transform: scale(1.1);
    box-shadow: 
        0 12px 32px rgba(0,0,0,0.35),
        0 0 0 4px rgba(255,255,255,0.2);
}

.play-btn:active {
    transform: scale(1.05);
}

.play-btn svg {
    width: 28px;
    height: 28px;
    fill: #2c5282;
    margin-left: 3px; /* Visual centering for play icon */
}

.time-display {
    color: rgba(255,255,255,0.95);
    font-size: 0.95em;
    font-weight: 600;
    min-width: 100px;
    font-variant-numeric: tabular-nums;
    letter-spacing: 0.03em;
}

/* Support both class names */
.progress-bar-container,
.progress-container {
    flex: 1;
    height: 10px;
    background: rgba(255,255,255,0.15);
    border-radius: 5px;
    cursor: pointer;
    position: relative;
    overflow: hidden;
    backdrop-filter: blur(4px);
}

.progress-bar-container:hover,
.progress-container:hover {
    height: 12px;
    transition: height 0.2s ease;
}

.progress-bar-fill,
.progress-bar {
    height: 100%;
    background: linear-gradient(90deg, #68d391, #48bb78, #38a169);
    border-radius: 5px;
    width: 0%;
    transition: width 0.1s linear;
    position: relative;
}

.progress-bar-fill::after,
.progress-bar::after {
    content: '';
    position: absolute;
    right: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 16px;
    height: 16px;
    background: white;
    border-radius: 50%;
    box-shadow: 0 2px 8px rgba(0,0,0,0.3);
    opacity: 0;
    transition: opacity 0.2s;
}

.progress-container:hover .progress-bar::after,
.progress-bar-container:hover .progress-bar-fill::after {
    opacity: 1;
}

.audio-bottom {
    display: flex;
    justify-content: space-between;
    align-items: center;
    color: white;
    flex-wrap: wrap;
    gap: 16px;
    position: relative;
    z-index: 1;
}

.volume-control {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.2em;
}

.volume-slider {
    width: 90px;
    height: 6px;
    background: rgba(255,255,255,0.2);
    border-radius: 3px;
    cursor: pointer;
    position: relative;
    transition: height 0.2s;
}

.volume-slider:hover {
    height: 8px;
}

.volume-fill {
    height: 100%;
    width: 70%;
    background: linear-gradient(90deg, rgba(255,255,255,0.8), white);
    border-radius: 3px;
}

/* Support both class names */
.speed-controls,
.speed-control {
    display: flex;
    align-items: center;
    gap: 8px;
}

.speed-control span {
    color: rgba(255,255,255,0.8);
    font-weight: 600;
    font-size: 0.85em;
    margin-right: 4px;
}

.speed-btn {
    padding: 8px 14px;
    background: rgba(255,255,255,0.1);
    border: 1px solid rgba(255,255,255,0.15);
    border-radius: 20px;
    color: rgba(255,255,255,0.9);
    font-size: 0.8em;
    font-weight: 700;
    cursor: pointer;
    transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

.speed-btn:hover {
    background: rgba(255,255,255,0.2);
    border-color: rgba(255,255,255,0.3);
    transform: translateY(-1px);
}

.speed-btn.active {
    background: white;
    color: #2c5282;
    border-color: white;
    box-shadow: 0 4px 12px rgba(255,255,255,0.25);
}

/* Transcript toggle - support multiple class patterns */
.transcript-toggle,
.transcript-btn {
    display: block;
    width: 100%;
    margin-top: 20px;
    padding: 14px 24px;
    background: rgba(255,255,255,0.08);
    border: 1px solid rgba(255,255,255,0.15);
    border-radius: 14px;
    color: white;
    font-size: 0.95em;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
    text-align: left;
    position: relative;
    z-index: 1;
}

.transcript-toggle:hover,
.transcript-btn:hover {
    background: rgba(255,255,255,0.15);
    border-color: rgba(255,255,255,0.25);
    transform: translateY(-2px);
}

.transcript-content {
    display: none;
    margin-top: 20px;
    padding: 24px;
    background: linear-gradient(135deg, rgba(255,255,255,0.98), rgba(255,255,255,0.95));
    border-radius: 16px;
    color: var(--text-primary);
    font-size: 0.95em;
    line-height: 1.9;
    position: relative;
    z-index: 1;
    box-shadow: 0 8px 24px rgba(0,0,0,0.1);
}

.transcript-content.show,
.transcript-content.visible {
    display: block;
    animation: slideDown 0.3s ease-out;
}

@keyframes slideDown {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.transcript-content p {
    margin-bottom: 14px;
    padding-left: 16px;
    border-left: 3px solid transparent;
    transition: all 0.2s;
}

.transcript-content p:hover {
    border-left-color: var(--brand-orange);
    background: var(--brand-orange-light);
    margin-left: -8px;
    padding-left: 24px;
    border-radius: 0 8px 8px 0;
}

.transcript-content p strong {
    color: var(--brand-dark-blue);
}

.transcript-content p em {
    color: var(--brand-orange);
    font-style: normal;
    font-weight: 600;
}

/* ============================================
   LISTENING QUESTIONS - Premium Card Layout
   ============================================ */

.listening-questions {
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.listening-question {
    background: linear-gradient(135deg, #f8fafc, #f1f5f9);
    border-radius: 20px;
    padding: 28px;
    border: 2px solid var(--glass-border);
    position: relative;
    transition: all 0.3s ease;
    box-shadow: 0 4px 16px rgba(73, 105, 134, 0.08);
}

.listening-question:hover {
    border-color: var(--brand-medium-blue);
    box-shadow: 0 8px 24px rgba(73, 105, 134, 0.12);
    transform: translateY(-2px);
}

/* Question number badge */
.listening-question::before {
    content: 'Q';
    position: absolute;
    top: -12px;
    left: 24px;
    width: 32px;
    height: 32px;
    background: linear-gradient(135deg, var(--brand-orange), var(--brand-accent-orange));
    color: white;
    font-weight: 800;
    font-size: 0.9em;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 10px;
    box-shadow: 0 4px 12px rgba(234, 107, 60, 0.35);
}

.listening-question strong {
    display: block;
    font-family: var(--font-heading);
    font-size: 1.1em;
    font-weight: 700;
    color: var(--brand-dark-blue);
    margin-bottom: 20px;
    margin-top: 8px;
    line-height: 1.5;
}

/* Radio option labels */
.listening-question label {
    display: flex;
    align-items: center;
    gap: 14px;
    padding: 16px 20px;
    background: white;
    border: 2px solid var(--brand-light-blue);
    border-radius: 14px;
    cursor: pointer;
    transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
    margin-bottom: 10px;
    font-size: 0.95em;
    color: var(--text-primary);
    position: relative;
    overflow: hidden;
}

.listening-question label::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    height: 100%;
    width: 4px;
    background: transparent;
    transition: all 0.25s;
}

.listening-question label:hover {
    border-color: var(--brand-orange);
    background: linear-gradient(135deg, var(--brand-orange-light), white);
    transform: translateX(4px);
}

.listening-question label:hover::before {
    background: var(--brand-orange);
}

.listening-question input[type="radio"] {
    appearance: none;
    -webkit-appearance: none;
    width: 22px;
    height: 22px;
    border: 2px solid var(--brand-light-blue);
    border-radius: 50%;
    cursor: pointer;
    transition: all 0.2s;
    flex-shrink: 0;
    position: relative;
}

.listening-question input[type="radio"]:checked {
    border-color: var(--brand-orange);
    background: var(--brand-orange);
}

.listening-question input[type="radio"]:checked::after {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 8px;
    height: 8px;
    background: white;
    border-radius: 50%;
}

.listening-question input[type="radio"]:hover {
    border-color: var(--brand-orange);
}

/* Text input for listening questions */
.listening-question input[type="text"] {
    width: 100%;
    padding: 16px 20px;
    border: 2px solid var(--brand-light-blue);
    border-radius: 14px;
    font-size: 1em;
    font-family: var(--font-body);
    color: var(--text-primary);
    background: white;
    transition: all 0.3s;
    margin-top: 8px;
}

.listening-question input[type="text"]:focus {
    outline: none;
    border-color: var(--brand-orange);
    box-shadow: 0 0 0 4px var(--brand-orange-light);
}

.listening-question input[type="text"]::placeholder {
    color: var(--text-muted);
    font-style: italic;
}

.question-label {
    font-weight: 700;
    color: var(--brand-dark-blue);
    margin-bottom: 16px;
    font-size: 1.05em;
}

.radio-options {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.radio-option {
    display: flex;
    align-items: center;
    gap: 14px;
    padding: 14px 18px;
    background: white;
    border: 2px solid var(--brand-light-blue);
    border-radius: 12px;
    cursor: pointer;
    transition: all 0.25s;
}

.radio-option:hover {
    border-color: var(--brand-orange);
    background: var(--brand-orange-light);
    transform: translateX(4px);
}

.radio-option input[type="radio"] {
    accent-color: var(--brand-orange);
    width: 20px;
    height: 20px;
}

/* ============================================
   QUIZ SECTION
   ============================================ */

.quiz-container {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.quiz-card {
    background: var(--brand-blue-soft);
    border-radius: 16px;
    padding: 24px;
    position: relative;
    transition: all 0.3s;
}

.quiz-number {
    position: absolute;
    top: -10px;
    left: 20px;
    width: 30px;
    height: 30px;
    background: var(--brand-orange);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: 0.9em;
}

.quiz-question {
    font-weight: 600;
    color: var(--brand-dark-blue);
    margin-bottom: 16px;
    margin-top: 8px;
    font-size: 1.05em;
}

.quiz-options {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.quiz-option {
    display: flex;
    align-items: center;
    gap: 14px;
    padding: 14px 18px;
    background: white;
    border: 2px solid var(--glass-border);
    border-radius: 12px;
    cursor: pointer;
    transition: all 0.3s;
}

.quiz-option:hover {
    border-color: var(--brand-orange);
    background: var(--brand-orange-light);
}

.quiz-option.correct {
    background: var(--success-light);
    border-color: var(--success);
}

.quiz-option.incorrect {
    background: var(--error-light);
    border-color: var(--error);
}

.option-letter {
    width: 28px;
    height: 28px;
    border-radius: 50%;
    background: var(--brand-light-blue);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: 0.85em;
    color: var(--brand-dark-blue);
}

.quiz-option.correct .option-letter {
    background: var(--success);
    color: white;
}

.quiz-option.incorrect .option-letter {
    background: var(--error);
    color: white;
}

.option-text {
    font-size: 0.95em;
    color: var(--text-primary);
}

/* ============================================
   EXERCISE SECTION
   ============================================ */

.exercise-container {
    display: flex;
    flex-direction: column;
    gap: 16px;
    margin-bottom: 20px;
}

.exercise-card {
    background: var(--brand-blue-soft);
    border-radius: 14px;
    padding: 20px;
}

.exercise-header {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 12px;
}

.exercise-number {
    font-weight: 700;
    color: var(--brand-orange);
    font-size: 1.1em;
}

.exercise-prompt {
    color: var(--text-primary);
    margin-bottom: 12px;
    line-height: 1.6;
}

.exercise-input {
    width: 100%;
    padding: 14px 18px;
    border: 2px solid var(--brand-light-blue);
    border-radius: 10px;
    font-size: 0.95em;
    transition: all 0.3s;
}

.exercise-input:focus {
    outline: none;
    border-color: var(--brand-orange);
    box-shadow: 0 0 0 3px var(--brand-orange-light);
}

.exercise-input.correct {
    border-color: var(--success);
    background: var(--success-light);
}

.exercise-input.incorrect {
    border-color: var(--error);
    background: var(--error-light);
}

/* ============================================
   HINT BOX
   ============================================ */

.hint-box {
    display: none;
    margin-top: 12px;
    padding: 14px 18px;
    background: var(--warning-light);
    border: 2px solid var(--warning);
    border-radius: 10px;
    color: #92400e;
    font-size: 0.9em;
}

.hint-box.show {
    display: block;
}

.hint-box strong {
    color: var(--warning);
}

/* ============================================
   SPEAKING SECTION
   ============================================ */

.speaking-prompts {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.speaking-card {
    background: linear-gradient(135deg, var(--brand-blue-soft), #e8f4f8);
    border: 2px solid var(--brand-light-blue);
    border-radius: 16px;
    padding: 24px;
}

.speaking-label {
    font-weight: 700;
    color: var(--brand-dark-blue);
    margin-bottom: 10px;
    font-size: 1em;
}

.speaking-text {
    color: var(--text-secondary);
    line-height: 1.7;
}

.speaking-text strong {
    color: var(--brand-orange);
}

/* ============================================
   BUTTONS
   ============================================ */

.btn {
    padding: 12px 24px;
    border-radius: 12px;
    font-size: 0.95em;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
    border: none;
    display: inline-flex;
    align-items: center;
    gap: 8px;
}

.btn-primary {
    background: linear-gradient(135deg, var(--brand-orange), var(--brand-accent-orange));
    color: white;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(234,107,60,0.4);
}

.btn-secondary {
    background: var(--brand-blue-soft);
    color: var(--brand-dark-blue);
    border: 2px solid var(--brand-light-blue);
}

.btn-secondary:hover {
    background: var(--brand-light-blue);
}

.btn-success {
    background: linear-gradient(135deg, var(--success), #059669);
    color: white;
}

.btn-success:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(16,185,129,0.4);
}

.btn-hint {
    background: var(--warning-light);
    color: #92400e;
    border: 2px solid var(--warning);
}

.btn-hint:hover {
    background: #fde68a;
}

.btn-group,
.button-group {
    display: flex;
    gap: 12px;
    flex-wrap: wrap;
    margin-top: 20px;
}

/* Nav buttons within sections */
.nav-buttons {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 32px;
    padding-top: 24px;
    border-top: 2px solid var(--glass-border);
    gap: 16px;
}

.nav-btn-prev,
.nav-btn-next {
    padding: 14px 28px;
    border-radius: 14px;
    font-weight: 700;
    font-size: 0.95em;
    cursor: pointer;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    display: inline-flex;
    align-items: center;
    gap: 10px;
    border: none;
    font-family: var(--font-body);
}

.nav-btn-prev {
    background: var(--brand-blue-soft);
    color: var(--brand-dark-blue);
    border: 2px solid var(--brand-light-blue);
}

.nav-btn-prev:hover {
    background: var(--brand-light-blue);
    transform: translateX(-4px);
}

.nav-btn-next {
    background: linear-gradient(135deg, var(--brand-orange), var(--brand-accent-orange));
    color: white;
    box-shadow: 0 6px 20px rgba(234, 107, 60, 0.35);
}

.nav-btn-next:hover {
    transform: translateX(4px);
    box-shadow: 0 8px 28px rgba(234, 107, 60, 0.45);
}

.nav-btn-prev span,
.nav-btn-next span {
    font-size: 1.1em;
    transition: transform 0.2s;
}

.nav-btn-prev:hover span {
    transform: translateX(-3px);
}

.nav-btn-next:hover span {
    transform: translateX(3px);
}

/* ============================================
   LESSON NAVIGATION
   ============================================ */

.lesson-nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 32px;
    padding-top: 24px;
    border-top: 2px solid var(--glass-border);
}

.nav-arrow {
    padding: 12px 24px;
    background: var(--brand-orange);
    color: white;
    text-decoration: none;
    border-radius: 12px;
    font-weight: 600;
    transition: all 0.3s;
}

.nav-arrow:hover {
    background: var(--brand-accent-orange);
    transform: translateY(-2px);
}

.nav-arrow.prev {
    background: var(--brand-blue-soft);
    color: var(--brand-dark-blue);
}

.nav-arrow.prev:hover {
    background: var(--brand-light-blue);
}

.lesson-progress-bar {
    flex: 1;
    max-width: 300px;
    margin: 0 20px;
    text-align: center;
}

.progress-track {
    height: 8px;
    background: var(--brand-light-blue);
    border-radius: 4px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--success);
    border-radius: 4px;
    transition: width 0.3s;
}

.progress-text-bottom {
    font-size: 0.85em;
    color: var(--text-muted);
    margin-top: 8px;
}

/* ============================================
   LESSON VALIDATION (Two-Button System)
   ============================================ */

.lesson-validation {
    display: flex;
    justify-content: center;
    gap: 16px;
    padding: 24px 0;
    margin-top: 20px;
    border-top: 2px solid var(--glass-border);
    flex-wrap: wrap;
}

.btn-validate {
    background: linear-gradient(135deg, #2c5aa0, #1e4080);
    color: white;
    padding: 14px 28px;
    border-radius: 12px;
    font-weight: 600;
    font-size: 1em;
    cursor: pointer;
    border: none;
    transition: all 0.3s ease;
    box-shadow: 0 4px 15px rgba(44, 90, 160, 0.3);
}

.btn-validate:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(44, 90, 160, 0.4);
}

.btn-validate.validated {
    background: linear-gradient(135deg, #22c55e, #16a34a);
    box-shadow: 0 4px 15px rgba(34, 197, 94, 0.3);
}

.btn-validate:disabled {
    opacity: 0.7;
    cursor: not-allowed;
    transform: none;
}

.btn-next-lesson {
    background: var(--brand-blue-soft);
    color: var(--brand-dark-blue);
    padding: 14px 28px;
    border-radius: 12px;
    font-weight: 600;
    font-size: 1em;
    text-decoration: none;
    transition: all 0.3s ease;
    border: 2px solid var(--brand-light-blue);
}

.btn-next-lesson:hover:not(.disabled) {
    background: var(--brand-orange);
    color: white;
    border-color: var(--brand-orange);
    transform: translateY(-2px);
}

.btn-next-lesson.disabled {
    opacity: 0.5;
    pointer-events: none;
    cursor: not-allowed;
}

/* ============================================
   FOOTER
   ============================================ */

.footer {
    background: var(--bg-card);
    border-top: 2px solid var(--glass-border);
    padding: 24px;
    margin-top: 40px;
}

.footer-content {
    max-width: 1400px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 16px;
}

.footer-brand {
    display: flex;
    align-items: center;
    gap: 12px;
}

.footer-brand img {
    width: 36px;
    height: 36px;
    border-radius: 8px;
}

.footer-brand span {
    font-weight: 600;
    color: var(--text-secondary);
}

.footer-links {
    display: flex;
    gap: 20px;
}

.footer-link {
    color: var(--text-muted);
    font-size: 0.9em;
}

/* ============================================
   RESPONSIVE DESIGN
   ============================================ */

@media (max-width: 1024px) {
    .main-layout {
        grid-template-columns: 1fr;
    }

    .sidebar {
        position: relative;
        top: 0;
        max-height: none;
    }

    .sidebar-card {
        display: grid;
        grid-template-columns: 1fr auto;
        gap: 20px;
    }

    .section-nav {
        flex-direction: row;
        flex-wrap: wrap;
        gap: 8px;
    }

    .section-nav-item {
        padding: 8px 14px;
    }

    .nav-label { display: none; }
}

@media (max-width: 768px) {
    .header-content { flex-direction: column; gap: 12px; }
    .header-nav { justify-content: center; }
    .main-layout { padding: 20px 16px; }
    .content-section { padding: 24px 20px; }
    .grammar-grid { grid-template-columns: 1fr; }
    .context-grid { grid-template-columns: 1fr; }
    .objectives-grid { grid-template-columns: 1fr; }
    .lesson-nav { flex-direction: column; gap: 16px; }
    .lesson-progress-bar { max-width: 100%; margin: 0; }
    .sidebar-card { grid-template-columns: 1fr; }
    .progress-section { display: none; }

    .section-nav {
        display: grid;
        grid-template-columns: repeat(auto-fit, minmax(40px, 1fr));
        gap: 6px;
    }

    .section-nav-item {
        justify-content: center;
        padding: 10px;
    }
    
    .lesson-validation {
        flex-direction: column;
        align-items: center;
    }
    
    .btn-validate,
    .btn-next-lesson {
        width: 100%;
        max-width: 300px;
        text-align: center;
        justify-content: center;
    }
}

/* ============================================
   UTILITY CLASSES
   ============================================ */

.hidden { display: none !important; }
.text-center { text-align: center; }
.text-muted { color: var(--text-muted); }
.mt-1 { margin-top: 8px; }
.mt-2 { margin-top: 16px; }
.mt-3 { margin-top: 24px; }
.mb-1 { margin-bottom: 8px; }
.mb-2 { margin-bottom: 16px; }
.mb-3 { margin-bottom: 24px; }