/* 전역 스타일 */
:root {
    --primary-color: #6366f1;
    --primary-dark: #4f46e5;
    --secondary-color: #64748b;
    --success-color: #10b981;
    --danger-color: #ef4444;
    --warning-color: #f59e0b;
    --info-color: #06b6d4;
    --dark-color: #1e293b;
    --light-color: #f8fafc;
    --gradient-primary: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --gradient-secondary: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    --gradient-text: linear-gradient(135deg, #6366f1 0%, #8b5cf6 100%);
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);
}

* {
    box-sizing: border-box;
}

body {
    font-family: 'Inter', 'Noto Sans KR', -apple-system, BlinkMacSystemFont, sans-serif;
    line-height: 1.7;
    color: var(--dark-color);
    overflow-x: hidden;
}

/* 유틸리티 클래스 */
.text-gradient {
    background: var(--gradient-text);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    font-weight: 700;
}

/* 네비게이션 개선 */
.navbar {
    backdrop-filter: blur(20px);
    background: rgba(255, 255, 255, 0.95) !important;
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
    transition: all 0.3s ease;
    z-index: 1050;
}

.navbar-brand {
    font-weight: 800;
    font-size: 1.75rem;
    color: var(--primary-color) !important;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.navbar-brand i {
    font-size: 1.5rem;
    color: var(--primary-color);
}

.navbar-nav .nav-link {
    font-weight: 500;
    margin: 0 0.5rem;
    color: var(--dark-color) !important;
    transition: all 0.3s ease;
    position: relative;
}

.navbar-nav .nav-link:hover {
    color: var(--primary-color) !important;
}

.navbar-nav .nav-link::after {
    content: '';
    position: absolute;
    width: 0;
    height: 2px;
    bottom: 0;
    left: 50%;
    background: var(--gradient-primary);
    transition: all 0.3s ease;
    transform: translateX(-50%);
}

.navbar-nav .nav-link:hover::after {
    width: 100%;
}

/* Hero Section 완전 재설계 */
.hero-section {
    position: relative;
    min-height: 100vh;
    display: flex;
    align-items: center;
    overflow: hidden;
    background: linear-gradient(135deg, #1e3a8a 0%, #1e1b4b 100%);
    padding-top: 80px;
    margin-top: -80px;
}

.hero-background {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    z-index: 1;
}

.hero-particles {
    position: absolute;
    width: 100%;
    height: 100%;
    background-image: 
        radial-gradient(circle at 25% 25%, rgba(255,255,255,0.1) 1px, transparent 1px),
        radial-gradient(circle at 75% 75%, rgba(255,255,255,0.1) 1px, transparent 1px);
    background-size: 60px 60px;
    animation: float 20s ease-in-out infinite;
}

.hero-gradient {
    position: absolute;
    width: 100%;
    height: 100%;
    background: linear-gradient(135deg, 
        rgba(30, 58, 138, 0.95) 0%, 
        rgba(30, 27, 75, 0.95) 50%,
        rgba(15, 23, 42, 0.95) 100%);
}

.hero-section .container {
    position: relative;
    z-index: 2;
}

.hero-badge {
    display: inline-flex;
    align-items: center;
    padding: 0.5rem 1rem;
    background: rgba(255, 255, 255, 0.1);
    border: 1px solid rgba(255, 255, 255, 0.2);
    border-radius: 50px;
    color: white;
    font-size: 0.875rem;
    font-weight: 500;
    backdrop-filter: blur(10px);
}

.hero-title {
    font-size: clamp(2.5rem, 5vw, 4rem);
    font-weight: 800;
    line-height: 1.2;
    color: white !important;
    margin-bottom: 1.5rem;
}

.hero-subtitle {
    font-size: 1.25rem;
    font-weight: 400;
    color: rgba(255, 255, 255, 0.95);
    line-height: 1.6;
    text-shadow: 0 1px 2px rgba(0, 0, 0, 0.3);
}

.hero-actions {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
    align-items: center;
}

.hero-actions .btn {
    font-weight: 600;
    border-radius: 50px;
    transition: all 0.3s ease;
    box-shadow: var(--shadow-lg);
}

.hero-actions .btn-primary {
    background: rgba(255, 255, 255, 0.15);
    border: 2px solid rgba(255, 255, 255, 0.3);
    color: white;
    backdrop-filter: blur(10px);
}

.hero-actions .btn-primary:hover {
    background: white;
    color: var(--primary-color);
    transform: translateY(-2px);
    box-shadow: var(--shadow-xl);
}

.hero-actions .btn-outline-primary {
    background: transparent;
    border: 2px solid rgba(255, 255, 255, 0.3);
    color: white;
    backdrop-filter: blur(10px);
}

.hero-actions .btn-outline-primary:hover {
    background: rgba(255, 255, 255, 0.1);
    border-color: white;
    transform: translateY(-2px);
}

.hero-stats {
    margin-top: 3rem;
    color: white;
    background: rgba(0, 0, 0, 0.3);
    backdrop-filter: blur(10px);
    border-radius: 20px;
    padding: 2rem;
    border: 1px solid rgba(255, 255, 255, 0.2);
}

.hero-stats .stat-item {
    padding: 1rem 0;
}

.hero-stats .stat-number {
    font-size: 2.5rem;
    font-weight: 900;
    color: #ff8c42 !important;
    margin-bottom: 0.5rem;
    text-shadow: 0 2px 8px rgba(0, 0, 0, 0.7);
    filter: drop-shadow(0 2px 4px rgba(0, 0, 0, 0.8));
}

.hero-stats .stat-label {
    font-size: 1rem;
    color: rgba(255, 255, 255, 0.95) !important;
    margin: 0;
    text-shadow: 0 1px 4px rgba(0, 0, 0, 0.6);
    font-weight: 600;
}

/* Hero Visual Effects */
.hero-visual {
    position: relative;
    height: 600px;
}

.floating-card {
    position: absolute;
    background: rgba(255, 255, 255, 0.95);
    border-radius: 16px;
    padding: 1.5rem;
    box-shadow: var(--shadow-xl);
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.2);
    animation: float 6s ease-in-out infinite;
}

.card-1 {
    top: 20%;
    left: 10%;
    z-index: 3;
    animation-delay: 0s;
}

.card-2 {
    top: 10%;
    right: 15%;
    z-index: 2;
    animation-delay: 2s;
}

.card-3 {
    bottom: 30%;
    left: 5%;
    z-index: 2;
    animation-delay: 4s;
}

.hero-device {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 400px;
    height: 300px;
    z-index: 1;
}

.device-screen {
    width: 100%;
    height: 100%;
    background: #1a1a1a;
    border-radius: 20px;
    padding: 20px;
    box-shadow: var(--shadow-xl);
    border: 2px solid rgba(255, 255, 255, 0.1);
}

.video-interface {
    height: 100%;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
}

.video-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 10px;
    height: 200px;
    transition: all 0.3s ease;
}

/* 화면공유 모드 스타일 */
.video-grid.screen-sharing-mode {
    grid-template-columns: 1fr;
    height: calc(100vh - 200px);
    position: relative;
}

.video-grid.screen-sharing-mode .video-container:first-child {
    grid-column: 1;
    grid-row: 1;
    width: 100%;
    height: 100%;
}

.video-grid.screen-sharing-mode .video-container:last-child {
    position: absolute;
    top: 10px;
    right: 10px;
    width: 200px;
    height: 150px;
    z-index: 1000;
    border: 2px solid #fff;
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
}

.video-tile {
    background: #2a2a2a;
    border-radius: 12px;
    overflow: hidden;
    position: relative;
    display: flex;
    align-items: center;
    justify-content: center;
}

.video-avatar {
    width: 100%;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    color: white;
}

.video-avatar.teacher-1 {
    background: linear-gradient(135deg, #3b82f6 0%, #1d4ed8 100%);
}

.video-avatar.student-1 {
    background: linear-gradient(135deg, #f59e0b 0%, #d97706 100%);
}

.video-overlay {
    position: absolute;
    bottom: 10px;
    left: 10px;
    background: rgba(0, 0, 0, 0.7);
    color: white;
    padding: 4px 8px;
    border-radius: 6px;
    font-size: 0.75rem;
}

.control-bar {
    display: flex;
    justify-content: center;
    gap: 10px;
    padding: 15px 0;
}

.control-btn {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    border: none;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1rem;
    transition: all 0.3s ease;
}

.control-btn.active {
    background: var(--success-color);
    color: white;
}

.control-btn:not(.active) {
    background: #4a4a4a;
    color: #ccc;
}

.control-btn.end-call {
    background: var(--danger-color);
    color: white;
}

.avatar {
    width: 60px;
    height: 60px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    font-size: 1.25rem;
    color: white;
    flex-shrink: 0;
}

.avatar.teacher-1 {
    background: linear-gradient(135deg, #3b82f6 0%, #1d4ed8 100%);
}

.avatar.teacher-2 {
    background: linear-gradient(135deg, #10b981 0%, #059669 100%);
}

.avatar.student-1 {
    background: linear-gradient(135deg, #f59e0b 0%, #d97706 100%);
}

.avatar.student-2 {
    background: linear-gradient(135deg, #ef4444 0%, #dc2626 100%);
}

.avatar.student-3 {
    background: linear-gradient(135deg, #8b5cf6 0%, #7c3aed 100%);
}

.avatar.student-4 {
    background: linear-gradient(135deg, #ec4899 0%, #db2777 100%);
}

.progress {
    height: 8px;
    border-radius: 10px;
    background: rgba(255, 255, 255, 0.2);
}

.progress-bar {
    background: var(--gradient-primary);
    border-radius: 10px;
}

@keyframes float {
    0%, 100% { transform: translateY(0px); }
    50% { transform: translateY(-20px); }
}

.video-preview-card {
    background: #fff;
    border-radius: 15px;
    padding: 20px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.1);
    max-width: 400px;
    margin: 0 auto;
}

.fake-video-call {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 15px;
    padding: 20px;
    background: #f8f9fa;
    border-radius: 10px;
}

.video-participant {
    text-align: center;
    color: #333;
}

.video-participant span {
    display: block;
    margin-top: 10px;
    font-size: 0.9rem;
    font-weight: 500;
}

.video-controls {
    display: flex;
    justify-content: center;
    gap: 10px;
}

.video-controls .btn {
    border-radius: 50%;
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
}

/* Features Section 완전 재설계 */
.features-section {
    padding: 6rem 0;
    background: linear-gradient(180deg, #f8fafc 0%, #ffffff 100%);
    position: relative;
    opacity: 1;
    visibility: visible;
}

.features-section::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 1px;
    background: linear-gradient(90deg, transparent, rgba(99, 102, 241, 0.3), transparent);
}

.section-badge {
    display: inline-flex;
    align-items: center;
    padding: 0.5rem 1rem;
    background: rgba(99, 102, 241, 0.1);
    border: 1px solid rgba(99, 102, 241, 0.2);
    border-radius: 50px;
    color: var(--primary-color);
    font-size: 0.875rem;
    font-weight: 600;
    margin-bottom: 1rem;
}

.section-title {
    font-size: clamp(2rem, 4vw, 3rem);
    font-weight: 800;
    line-height: 1.2;
    color: var(--dark-color);
    margin-bottom: 1.5rem;
}

.section-subtitle {
    font-size: 1.125rem;
    color: var(--secondary-color);
    line-height: 1.7;
    margin-bottom: 0;
}

.features-grid {
    margin-top: 4rem;
}

.feature-card {
    background: white;
    border-radius: 20px;
    padding: 2rem;
    border: 1px solid rgba(148, 163, 184, 0.1);
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    position: relative;
    overflow: hidden;
    height: 100%;
    display: flex;
    flex-direction: column;
}

.feature-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--gradient-primary);
    transform: scaleX(0);
    transition: transform 0.4s ease;
}

.feature-card:hover::before {
    transform: scaleX(1);
}

.feature-card:hover {
    transform: translateY(-8px);
    box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.15);
    border-color: rgba(99, 102, 241, 0.2);
}

.feature-icon-wrapper {
    position: relative;
    margin-bottom: 1.5rem;
    width: 80px;
    height: 80px;
}

.feature-icon {
    width: 80px;
    height: 80px;
    border-radius: 20px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    color: white;
    position: relative;
    z-index: 2;
    transition: all 0.4s ease;
}

.feature-icon.video-icon {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
}

.feature-icon.screen-icon {
    background: linear-gradient(135deg, #10b981 0%, #059669 100%);
}

.feature-icon.record-icon {
    background: linear-gradient(135deg, #ef4444 0%, #dc2626 100%);
}

.feature-icon.mobile-icon {
    background: linear-gradient(135deg, #06b6d4 0%, #0891b2 100%);
}

.feature-icon.users-icon {
    background: linear-gradient(135deg, #f59e0b 0%, #d97706 100%);
}

.feature-icon.security-icon {
    background: linear-gradient(135deg, #8b5cf6 0%, #7c3aed 100%);
}

.icon-bg {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 120px;
    height: 120px;
    border-radius: 50%;
    background: radial-gradient(circle, rgba(99, 102, 241, 0.1) 0%, transparent 70%);
    transition: all 0.4s ease;
    z-index: 1;
}

.feature-card:hover .icon-bg {
    transform: translate(-50%, -50%) scale(1.5);
    opacity: 0.7;
}

.feature-card:hover .feature-icon {
    transform: scale(1.1);
}

.feature-content {
    flex: 1;
    display: flex;
    flex-direction: column;
}

.feature-title {
    font-size: 1.375rem;
    font-weight: 700;
    color: var(--dark-color);
    margin-bottom: 1rem;
    line-height: 1.3;
}

.feature-description {
    color: var(--secondary-color);
    line-height: 1.7;
    margin-bottom: 1.5rem;
    flex: 1;
}

.feature-highlight {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
    margin-top: auto;
}

.feature-highlight .badge {
    font-size: 0.75rem;
    font-weight: 600;
    padding: 0.375rem 0.75rem;
    border-radius: 12px;
    border: none;
}

/* Statistics Section */
.stats-section {
    padding: 6rem 0;
    background: linear-gradient(135deg, #1e3a8a 0%, #1e1b4b 100%);
    color: white;
    position: relative;
    overflow: hidden;
    opacity: 1;
    visibility: visible;
}

.stats-section::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: url('data:image/svg+xml,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100"><defs><pattern id="grain" width="100" height="100" patternUnits="userSpaceOnUse"><circle cx="25" cy="25" r="1" fill="rgba(255,255,255,0.05)"/><circle cx="75" cy="75" r="1" fill="rgba(255,255,255,0.05)"/></pattern></defs><rect width="100" height="100" fill="url(%23grain)"/></svg>');
    opacity: 0.5;
}

.stats-section .container {
    position: relative;
    z-index: 2;
}

.stats-section .section-title {
    color: white !important;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
}

.stats-section .section-subtitle {
    color: rgba(255, 255, 255, 0.95) !important;
    text-shadow: 0 1px 2px rgba(0, 0, 0, 0.2);
}

.stat-card {
    background: rgba(255, 255, 255, 0.95);
    border: 1px solid rgba(255, 255, 255, 0.8);
    border-radius: 20px;
    padding: 2rem;
    text-align: center;
    backdrop-filter: blur(15px);
    transition: all 0.5s cubic-bezier(0.4, 0, 0.2, 1);
    height: 100%;
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
}

.stat-card:hover {
    transform: translateY(-15px) scale(1.02);
    background: rgba(255, 255, 255, 1);
    border-color: rgba(255, 255, 255, 1);
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.15);
}

.stat-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto 1.5rem;
    background: linear-gradient(135deg, #3b82f6, #1d4ed8);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    color: white;
    box-shadow: 0 8px 24px rgba(59, 130, 246, 0.3);
}

.stat-number {
    font-size: 3rem;
    font-weight: 800;
    color: #1f2937 !important;
    margin-bottom: 0.5rem;
    line-height: 1;
    opacity: 1;
    visibility: visible;
}

.stat-suffix {
    font-size: 2rem;
    font-weight: 800;
    color: #1f2937;
    display: inline;
}

.stat-label {
    font-size: 1.125rem;
    font-weight: 600;
    color: #4b5563 !important;
    margin-bottom: 1rem;
    opacity: 1;
    visibility: visible;
}

.stat-growth {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    color: #059669;
    font-size: 0.875rem;
    font-weight: 600;
}

.stat-growth i {
    font-size: 0.75rem;
}

/* Activity Feed */
.activity-feed {
    background: rgba(255, 255, 255, 0.15);
    border: 1px solid rgba(255, 255, 255, 0.3);
    border-radius: 20px;
    padding: 2rem;
    backdrop-filter: blur(10px);
    margin-top: 4rem;
    opacity: 1;
    visibility: visible;
}

.activity-header h4 {
    color: white !important;
    font-weight: 700;
    text-shadow: 0 1px 2px rgba(0, 0, 0, 0.3);
}

.activity-header p {
    color: rgba(255, 255, 255, 0.9) !important;
}

.activity-list {
    max-height: 400px;
    overflow-y: auto;
}

.activity-item {
    display: flex;
    align-items: center;
    padding: 1rem 0;
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.activity-item:last-child {
    border-bottom: none;
}

.activity-avatar {
    margin-right: 1rem;
    flex-shrink: 0;
}

.activity-avatar .avatar {
    width: 50px;
    height: 50px;
    font-size: 0.875rem;
    border: 2px solid rgba(255, 255, 255, 0.2);
}

.activity-content {
    flex: 1;
}

.activity-text {
    color: rgba(255, 255, 255, 0.95);
    margin-bottom: 0.25rem;
    font-size: 0.95rem;
}

.activity-time {
    color: rgba(255, 255, 255, 0.6);
    font-size: 0.8rem;
}

.activity-badge {
    margin-left: 1rem;
    flex-shrink: 0;
}

/* Testimonials Section */
.testimonials-section {
    padding: 6rem 0;
    background: #f8fafc;
    opacity: 1;
    visibility: visible;
}

/* 후기 섹션 가시성 강제 */
.testimonials-section * {
    opacity: 1 !important;
    visibility: visible !important;
}

.testimonials-section .testimonial-card {
    background: white !important;
}

.testimonial-card {
    background: white;
    border-radius: 24px;
    padding: 2rem;
    border: 1px solid rgba(148, 163, 184, 0.1);
    transition: all 0.4s ease;
    height: 100%;
    display: flex;
    flex-direction: column;
    position: relative;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.05);
}

.testimonial-card::before {
    content: '';
    position: absolute;
    top: -2px;
    left: -2px;
    right: -2px;
    bottom: -2px;
    background: var(--gradient-primary);
    border-radius: 24px;
    opacity: 0;
    transition: opacity 0.4s ease;
    z-index: -1;
}

.testimonial-card:hover::before {
    opacity: 1;
}

.testimonial-card:hover {
    transform: translateY(-8px);
    box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.15);
    background: #ffffff;
}

.testimonial-rating {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.stars {
    display: flex;
    gap: 0.25rem;
}

.stars i {
    color: #ffc107;
    font-size: 1.25rem;
}

.rating-text {
    font-weight: 700;
    color: #1f2937 !important;
    font-size: 1.125rem;
}

.testimonial-content {
    flex: 1;
    margin-bottom: 2rem;
}

.testimonial-text {
    font-size: 1.125rem;
    line-height: 1.7;
    color: #374151 !important;
    font-style: italic;
    position: relative;
    font-weight: 400;
}

.testimonial-text::before {
    content: '"';
    font-size: 4rem;
    color: rgba(99, 102, 241, 0.15);
    position: absolute;
    top: -1rem;
    left: -1rem;
    font-family: serif;
    line-height: 1;
    z-index: -1;
}

.testimonial-author {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.author-avatar .avatar {
    width: 60px;
    height: 60px;
    font-size: 1rem;
    border: 3px solid rgba(99, 102, 241, 0.1);
}

.author-info {
    flex: 1;
}

.author-name {
    font-size: 1.125rem;
    font-weight: 700;
    color: #1f2937 !important;
    margin-bottom: 0.25rem;
}

.author-details {
    color: #6b7280 !important;
    font-size: 0.9rem;
    margin-bottom: 0.5rem;
    font-weight: 500;
}

.testimonial-meta span {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    background: rgba(99, 102, 241, 0.1);
    color: var(--primary-color);
    border-radius: 12px;
    font-size: 0.8rem;
    font-weight: 600;
}

/* Counter Animation */
@keyframes countUp {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}

.stat-number {
    animation: countUp 0.6s ease-out;
}

/* 통계 섹션 가시성 강제 */
.stats-section * {
    opacity: 1 !important;
    visibility: visible !important;
}

.stats-section .stat-card {
    display: block !important;
}

.stats-section .stat-number {
    display: block !important;
}

/* Step Cards */
.step-card {
    padding: 30px 20px;
}

.step-number {
    width: 60px;
    height: 60px;
    background: var(--primary-color);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    font-weight: bold;
    margin: 0 auto 20px;
}

/* CTA Section */
.cta-section {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
}

/* 반응형 디자인 */
@media (max-width: 768px) {
    .hero-section {
        text-align: center;
        min-height: auto;
        padding: 60px 0;
    }
    
    .display-4 {
        font-size: 2.5rem;
    }
    
    .video-preview-card {
        margin-top: 30px;
    }
    
    .fake-video-call {
        flex-direction: column;
        gap: 20px;
    }
    
    .d-flex.gap-3 {
        flex-direction: column;
    }
    
    .btn-lg {
        width: 100%;
    }
}

/* 로그인/회원가입 페이지 */
.auth-container {
    min-height: 100vh;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    display: flex;
    align-items: center;
    justify-content: center;
}

.auth-card {
    background: white;
    border-radius: 15px;
    box-shadow: 0 15px 35px rgba(0,0,0,0.1);
    overflow: hidden;
    max-width: 900px;
    width: 100%;
}

.auth-form-section {
    padding: 40px;
}

.auth-info-section {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 40px;
    display: flex;
    flex-direction: column;
    justify-content: center;
}

.form-floating {
    margin-bottom: 1rem;
}

/* 체크박스 크기 조정 */
.form-check-lg .form-check-input {
    width: 1.5em;
    height: 1.5em;
    margin-top: 0.15em;
    cursor: pointer;
}

.form-check-lg .form-check-label {
    font-size: 1.1rem;
    cursor: pointer;
    padding-left: 0.5rem;
}

.form-check-lg {
    padding: 0.75rem;
    border: 1px solid #dee2e6;
    border-radius: 0.375rem;
    transition: all 0.2s ease;
}

.form-check-lg:hover {
    background-color: #f8f9fa;
    border-color: #0d6efd;
}

.form-check-lg input:checked ~ label {
    font-weight: 600;
    color: #0d6efd;
}

/* 대시보드 스타일 */
.dashboard-sidebar {
    background: #343a40;
    min-height: 100vh;
    position: fixed;
    top: 0;
    left: 0;
    width: 250px;
    z-index: 1000;
    transition: transform 0.3s ease;
}

.dashboard-sidebar .nav-link {
    color: #fff;
    padding: 15px 20px;
    border-bottom: 1px solid #495057;
}

.dashboard-sidebar .nav-link:hover,
.dashboard-sidebar .nav-link.active {
    background-color: #495057;
    color: #fff;
}

.dashboard-main {
    margin-left: 250px;
    padding: 20px;
}

/* 세션 페이지 스타일 */
.session-container {
    height: 100vh;
    background: #1a1a1a;
    color: white;
    display: flex;
    flex-direction: column;
}

.video-grid {
    flex: 1;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 10px;
    padding: 10px;
}

.video-container {
    background: #333;
    border-radius: 10px;
    position: relative;
    overflow: hidden;
}

.video-container video {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.video-overlay {
    position: absolute;
    bottom: 10px;
    left: 10px;
    background: rgba(0,0,0,0.7);
    padding: 5px 10px;
    border-radius: 5px;
    font-size: 0.8rem;
}

.session-controls {
    background: #2a2a2a;
    padding: 20px;
    display: flex;
    justify-content: center;
    gap: 15px;
}

.session-controls .btn {
    border-radius: 50%;
    width: 50px;
    height: 50px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.chat-panel {
    position: fixed;
    right: 0;
    top: 0;
    width: 300px;
    height: 100vh;
    background: white;
    color: #333;
    transform: translateX(100%);
    transition: transform 0.3s ease;
    z-index: 1001;
}

.chat-panel.show {
    transform: translateX(0);
}

.chat-header {
    background: var(--primary-color);
    color: white;
    padding: 15px;
}

.chat-messages {
    flex: 1;
    overflow-y: auto;
    padding: 15px;
}

.chat-input {
    padding: 15px;
    border-top: 1px solid #eee;
}

/* 모바일 대응 */
@media (max-width: 768px) {
    .dashboard-sidebar {
        transform: translateX(-100%);
    }
    
    .dashboard-sidebar.show {
        transform: translateX(0);
    }
    
    .dashboard-main {
        margin-left: 0;
    }
    
    .video-grid {
        grid-template-columns: 1fr;
    }
    
    .auth-card {
        margin: 15px;
    }
    
    .auth-info-section {
        display: none;
    }
    
    .chat-panel {
        width: 100%;
    }
}

/* 유틸리티 클래스 */
.cursor-pointer {
    cursor: pointer;
}

.text-truncate-2 {
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.fade-in {
    opacity: 0;
    animation: fadeIn 0.5s ease-in forwards;
}

@keyframes fadeIn {
    to {
        opacity: 1;
    }
}

/* 스크롤바 스타일링 */
::-webkit-scrollbar {
    width: 8px;
}

::-webkit-scrollbar-track {
    background: #f1f1f1;
}

::-webkit-scrollbar-thumb {
    background: #ccc;
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: #999;
}

/* ȭ��Ʈ���� �������� ��Ÿ�� */
.whiteboard-overlay { position: fixed; top: 0; left: 0; width: 100%; height: 100%; background: rgba(0, 0, 0, 0.95); z-index: 9999; display: none; flex-direction: column; }
.whiteboard-overlay.active { display: flex; }
.whiteboard-header { background: #1a1a1a; padding: 15px 20px; border-bottom: 2px solid #444; display: flex; justify-content: space-between; align-items: center; flex-shrink: 0; }
.whiteboard-title { color: white; margin: 0; font-size: 1.2rem; display: flex; align-items: center; gap: 10px; }
.whiteboard-toolbar { background: #2a2a2a; padding: 10px 20px; border-bottom: 1px solid #444; display: flex; flex-wrap: wrap; gap: 10px; align-items: center; flex-shrink: 0; }
.whiteboard-content { flex: 1; display: flex; overflow: hidden; position: relative; }
.whiteboard-canvas-wrapper { flex: 1; display: flex; align-items: center; justify-content: center; padding: 20px; overflow: auto; }

/* PIP 비디오 스타일 */
.whiteboard-pip-video { 
    position: absolute; 
    top: 20px; 
    right: 20px; 
    width: 300px; 
    height: 225px; 
    border: 3px solid #007bff; 
    border-radius: 10px; 
    overflow: hidden; 
    box-shadow: 0 5px 20px rgba(0, 0, 0, 0.5); 
    z-index: 10; 
    background: #000; 
    transition: all 0.3s ease;
}

.whiteboard-pip-video video {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.whiteboard-pip-header {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    background: rgba(0, 0, 0, 0.8);
    padding: 5px 10px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: move;
    user-select: none;
}

.whiteboard-pip-name {
    color: white;
    font-size: 12px;
    font-weight: bold;
}

.whiteboard-pip-close {
    background: #dc3545;
    border: none;
    color: white;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    cursor: pointer;
    font-size: 14px;
    line-height: 1;
    padding: 0;
}

.whiteboard-pip-close:hover {
    background: #c82333;
}

/* 두 번째 PIP 비디오는 아래에 배치 */
#pipRemoteVideo {
    top: 260px !important;
}

/* 강사 승인 관리 스타일 */
.avatar-circle {
    width: 50px;
    height: 50px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
    flex-shrink: 0;
}

.tutor-approval-stats .card {
    border: none;
    border-radius: 12px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    transition: transform 0.2s;
}

.tutor-approval-stats .card:hover {
    transform: translateY(-2px);
}

.tutor-approval-stats .card-body {
    padding: 1.5rem;
}

.tutor-approval-stats .display-4 {
    font-weight: 700;
    margin-bottom: 0.5rem;
}

.tutor-approval-stats .text-muted {
    font-size: 0.9rem;
    font-weight: 500;
}

.pending-tutors-list .card {
    border: none;
    border-radius: 12px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.08);
    transition: all 0.2s;
}

.pending-tutors-list .card:hover {
    box-shadow: 0 4px 16px rgba(0,0,0,0.15);
    transform: translateY(-1px);
}

.pending-tutors-list .card-body {
    padding: 1.25rem;
}

.pending-tutors-list .card-title {
    font-weight: 600;
    color: #2c3e50;
}

.pending-tutors-list .btn {
    font-weight: 500;
    border-radius: 8px;
    transition: all 0.2s;
}

.pending-tutors-list .btn:hover {
    transform: translateY(-1px);
}

.refresh-btn {
    border-radius: 8px;
    font-weight: 500;
    padding: 0.5rem 1rem;
}

.refresh-btn:hover {
    transform: translateY(-1px);
}

/* Materials Section Styles */
.material-card {
    background: white;
    border-radius: 16px;
    padding: 2rem;
    text-align: center;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
    border: 1px solid rgba(0, 0, 0, 0.05);
    transition: all 0.3s ease;
}

.material-card:hover {
    transform: translateY(-8px);
    box-shadow: 0 12px 40px rgba(0, 0, 0, 0.15);
}

.material-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto 1.5rem;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    color: white;
}

.material-card h4 {
    color: #2d3748;
    font-weight: 700;
    margin-bottom: 1rem;
}

.material-card p {
    color: #718096;
    margin-bottom: 1.5rem;
}

.material-stats {
    display: flex;
    justify-content: space-around;
    color: #4a5568;
    font-size: 0.875rem;
    font-weight: 500;
}

.material-stats span {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.material-stats i {
    color: #667eea;
}

/* Product Cards */
.product-card {
    background: white;
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.08);
    transition: all 0.3s ease;
    height: 100%;
}

.product-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.15);
}

.product-image {
    position: relative;
    padding: 2rem;
    background: linear-gradient(135deg, #f7fafc 0%, #edf2f7 100%);
    text-align: center;
    min-height: 120px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.product-badge {
    position: absolute;
    top: 10px;
    right: 10px;
    background: #ff6b6b;
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.75rem;
    font-weight: 600;
}

.product-info {
    padding: 1.5rem;
}

.product-info h5 {
    color: #2d3748;
    font-weight: 600;
    margin-bottom: 0.5rem;
    font-size: 1rem;
}

.product-author {
    color: #718096;
    font-size: 0.875rem;
    margin-bottom: 1rem;
}

.product-rating {
    margin-bottom: 1rem;
    font-size: 0.875rem;
}

.product-price {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.product-price .price {
    font-size: 1.25rem;
    font-weight: 700;
    color: #667eea;
}

.product-price .original-price {
    font-size: 1rem;
    color: #a0aec0;
    text-decoration: line-through;
}

/* Disclaimer Section */
.disclaimer-section {
    margin-top: 3rem;
}

.disclaimer-card {
    background: #f8fafc;
    border: 2px solid #e2e8f0;
    border-radius: 16px;
    padding: 2rem;
}

.disclaimer-card h4 {
    color: #2d3748;
    font-weight: 700;
    margin-bottom: 1.5rem;
    text-align: center;
}

.disclaimer-content h6 {
    color: #4a5568;
    font-weight: 600;
    margin-bottom: 1rem;
}

.disclaimer-list {
    list-style: none;
    padding: 0;
}

.disclaimer-list li {
    padding: 0.5rem 0;
    color: #718096;
    position: relative;
    padding-left: 1.5rem;
}

.disclaimer-list li:before {
    content: "•";
    color: #cbd5e0;
    position: absolute;
    left: 0;
}

.disclaimer-notice {
    background: #fff5f5;
    border: 1px solid #fed7d7;
    border-radius: 8px;
    padding: 1.5rem;
}

.disclaimer-notice p strong {
    color: #c53030;
}

.disclaimer-notice a {
    color: #667eea;
    text-decoration: none;
}

.disclaimer-notice a:hover {
    text-decoration: underline;
}

/* Sell Materials CTA */
.sell-materials-cta {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 3rem 2rem;
    border-radius: 20px;
    margin: 2rem 0;
}

.sell-materials-cta h3 {
    font-weight: 700;
    margin-bottom: 1rem;
}

.sell-materials-cta .lead {
    margin-bottom: 2rem;
    opacity: 0.9;
}

.sell-materials-cta .btn-primary {
    background: white;
    border-color: white;
    color: #667eea;
    font-weight: 600;
}

.sell-materials-cta .btn-primary:hover {
    background: #f7fafc;
    border-color: #f7fafc;
    transform: translateY(-2px);
}

.sell-materials-cta .btn-outline-primary {
    border-color: white;
    color: white;
    font-weight: 600;
}

.sell-materials-cta .btn-outline-primary:hover {
    background: white;
    border-color: white;
    color: #667eea;
    transform: translateY(-2px);
}

/* AI 튜터 패널 스타일 */
.ai-panel {
    position: fixed;
    top: 80px;
    right: 20px;
    width: 350px;
    z-index: 1002;
    transition: all 0.3s ease;
}

.ai-panel .card {
    border: none;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
}

.ai-panel .card-header {
    border-bottom: none;
    font-weight: 600;
}

.ai-panel .fs-5 {
    font-size: 1.5rem !important;
}

.ai-panel small {
    font-size: 0.75rem;
    font-weight: 500;
}

.ai-panel .alert {
    font-size: 0.875rem;
}

#generatedProblem {
    margin-top: 1rem;
}

#generatedProblem .bg-light {
    background-color: #f8f9fa !important;
}