:root {
    --primary-color: #3498db;
    --primary-dark: #2980b9;
    --secondary-color: #2c3e50;
    --secondary-light: #34495e;
    --success-color: #27ae60;
    --warning-color: #f39c12;
    --danger-color: #e74c3c;
    --light-color: #ecf0f1;
    --dark-color: #2c3e50;
    --sidebar-width: 280px;
    --header-height: 56px;
    --transition-speed: 0.3s;
    --border-radius: 12px;
    --shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
    --shadow-hover: 0 8px 30px rgba(0, 0, 0, 0.15);
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    line-height: 1.6;
    color: #333;
}

/* Auth Pages */
.auth-body {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
}

.auth-card {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    padding: 3rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-hover);
    width: 100%;
    max-width: 450px;
    border: 1px solid rgba(255, 255, 255, 0.2);
    animation: slideUp 0.6s ease-out;
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Main Layout */
.main-container {
    display: flex;
    min-height: 100vh;
    background: #f8f9fa;
}

/* Sidebar */
.sidebar {
    width: var(--sidebar-width);
    background: linear-gradient(180deg, var(--secondary-color) 0%, var(--secondary-light) 100%);
    color: white;
    position: fixed;
    top: var(--header-height);
    left: 0;
    height: calc(100vh - var(--header-height));
    overflow-y: auto;
    transition: all var(--transition-speed) ease;
    z-index: 1000;
    box-shadow: 2px 0 10px rgba(0, 0, 0, 0.1);
}

.sidebar-sticky {
    position: relative;
    top: 0;
    height: 100%;
    padding-top: 1rem;
    overflow-x: hidden;
    overflow-y: auto;
}

.sidebar-header {
    padding: 1.5rem 1rem;
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
    margin-bottom: 1rem;
}

.sidebar-header h4 {
    color: white;
    font-weight: 600;
    font-size: 1.1rem;
}

.sidebar .nav-link {
    color: rgba(255, 255, 255, 0.9);
    padding: 0.75rem 1.5rem;
    margin: 0.25rem 1rem;
    border-radius: var(--border-radius);
    transition: all var(--transition-speed) ease;
    font-weight: 500;
    display: flex;
    align-items: center;
    gap: 0.75rem;
    position: relative;
    overflow: hidden;
}

.sidebar .nav-link::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.1), transparent);
    transition: left 0.5s ease;
}

.sidebar .nav-link:hover::before {
    left: 100%;
}

.sidebar .nav-link:hover {
    background-color: rgba(255, 255, 255, 0.15);
    color: white;
    transform: translateX(5px);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
}

.sidebar .nav-link.active {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    color: white;
    box-shadow: 0 4px 15px rgba(52, 152, 219, 0.4);
    transform: translateX(5px);
}

.sidebar .nav-link i {
    font-size: 1.1rem;
    width: 20px;
    text-align: center;
}

.sidebar-heading {
    color: rgba(255, 255, 255, 0.6);
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 1px;
    padding: 1rem 1.5rem;
    margin-top: 1rem;
}

.sidebar-footer {
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    margin-top: auto;
}

/* Header */
.navbar {
    background: linear-gradient(135deg, var(--secondary-color), var(--secondary-light));
    box-shadow: 0 2px 20px rgba(0, 0, 0, 0.1);
    height: var(--header-height);
    border: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1030;
}

.navbar-brand {
    font-weight: 700;
    color: white !important;
    font-size: 1.5rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.navbar-brand i {
    color: var(--primary-color);
}

/* Main Content */
.main-content {
    margin-left: var(--sidebar-width);
    padding: 2rem;
    width: calc(100% - var(--sidebar-width));
    min-height: 100vh;
    background: #f8f9fa;
    margin-top: var(--header-height);
}

/* Cards */
.card {
    border: none;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    transition: all var(--transition-speed) ease;
    background: white;
    overflow: hidden;
}

.card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-hover);
}

.card-header {
    background: linear-gradient(135deg, white, #f8f9fa);
    border-bottom: 1px solid rgba(0, 0, 0, 0.05);
    padding: 1.25rem 1.5rem;
    font-weight: 600;
}

.card-title {
    color: var(--dark-color);
    font-weight: 600;
    margin-bottom: 0.5rem;
}

/* Buttons */
.btn {
    border-radius: var(--border-radius);
    font-weight: 500;
    padding: 0.75rem 1.5rem;
    transition: all var(--transition-speed) ease;
    border: none;
    position: relative;
    overflow: hidden;
}

.btn::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 0;
    height: 0;
    background: rgba(255, 255, 255, 0.2);
    border-radius: 50%;
    transition: all 0.6s ease;
    transform: translate(-50%, -50%);
}

.btn:hover::before {
    width: 300px;
    height: 300px;
}

.btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(0, 0, 0, 0.15);
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    box-shadow: 0 4px 15px rgba(52, 152, 219, 0.3);
}

.btn-primary:hover {
    background: linear-gradient(135deg, var(--primary-dark), var(--primary-color));
    box-shadow: 0 6px 20px rgba(52, 152, 219, 0.4);
}

.btn-success {
    background: linear-gradient(135deg, var(--success-color), #229954);
    box-shadow: 0 4px 15px rgba(39, 174, 96, 0.3);
}

.btn-warning {
    background: linear-gradient(135deg, var(--warning-color), #e67e22);
    box-shadow: 0 4px 15px rgba(243, 156, 18, 0.3);
}

.btn-danger {
    background: linear-gradient(135deg, var(--danger-color), #c0392b);
    box-shadow: 0 4px 15px rgba(231, 76, 60, 0.3);
}

/* Stats Cards */
.stats-card {
    background: linear-gradient(135deg, #667eea, #764ba2);
    color: white;
    border-radius: var(--border-radius);
    padding: 1.5rem;
    margin-bottom: 1.5rem;
    transition: all var(--transition-speed) ease;
    position: relative;
    overflow: hidden;
}

.stats-card::before {
    content: '';
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: linear-gradient(45deg, transparent, rgba(255, 255, 255, 0.1), transparent);
    transform: rotate(45deg);
    transition: all 0.6s ease;
}

.stats-card:hover::before {
    transform: rotate(45deg) translate(50%, 50%);
}

.stats-card:hover {
    transform: translateY(-5px) scale(1.02);
    box-shadow: var(--shadow-hover);
}

/* Progress bars */
.progress {
    height: 10px;
    border-radius: 10px;
    background: rgba(0, 0, 0, 0.1);
    overflow: hidden;
    box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.2);
}

.progress-bar {
    background: linear-gradient(90deg, var(--primary-color), var(--primary-dark));
    border-radius: 10px;
    transition: width 1s ease-in-out;
    position: relative;
    overflow: hidden;
}

.progress-bar::after {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.4), transparent);
    animation: shimmer 2s infinite;
}

@keyframes shimmer {
    0% { left: -100%; }
    100% { left: 100%; }
}

/* Tables */
.table {
    background: white;
    border-radius: var(--border-radius);
    overflow: hidden;
    box-shadow: var(--shadow);
}

.table th {
    background: linear-gradient(135deg, #f8f9fa, #e9ecef);
    border: none;
    font-weight: 600;
    color: var(--dark-color);
    padding: 1rem;
}

.table td {
    padding: 1rem;
    border-color: rgba(0, 0, 0, 0.05);
    vertical-align: middle;
}

/* Forms */
.form-control {
    border-radius: var(--border-radius);
    border: 2px solid #e9ecef;
    padding: 0.75rem 1rem;
    transition: all var(--transition-speed) ease;
    font-size: 0.95rem;
}

.form-control:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 0.2rem rgba(52, 152, 219, 0.25);
    transform: translateY(-2px);
}

.form-label {
    font-weight: 600;
    color: var(--dark-color);
    margin-bottom: 0.5rem;
}

/* Alerts */
.alert {
    border-radius: var(--border-radius);
    border: none;
    padding: 1rem 1.5rem;
    box-shadow: var(--shadow);
    animation: slideIn 0.5s ease-out;
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateX(-20px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

/* Badges */
.badge {
    padding: 0.5em 0.75em;
    border-radius: 20px;
    font-weight: 500;
    font-size: 0.75rem;
}

/* Lesson cards */
.lesson-card {
    transition: all var(--transition-speed) ease;
    border-left: 4px solid var(--primary-color);
    position: relative;
    overflow: hidden;
}

.lesson-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(52, 152, 219, 0.1), transparent);
    transition: left 0.6s ease;
}

.lesson-card:hover::before {
    left: 100%;
}

.lesson-card:hover {
    transform: translateX(8px) translateY(-3px);
    box-shadow: var(--shadow-hover);
}

/* Quiz styles */
.quiz-question {
    background: white;
    padding: 1.5rem;
    border-radius: var(--border-radius);
    margin-bottom: 1.5rem;
    box-shadow: var(--shadow);
    transition: all var(--transition-speed) ease;
}

.quiz-question:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-hover);
}

.quiz-option {
    padding: 1rem 1.25rem;
    margin: 0.75rem 0;
    border: 2px solid #e9ecef;
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: all var(--transition-speed) ease;
    background: white;
}

.quiz-option:hover {
    border-color: var(--primary-color);
    background-color: #f8f9fa;
    transform: translateX(5px);
}

.quiz-option.selected {
    border-color: var(--primary-color);
    background-color: rgba(52, 152, 219, 0.1);
    transform: translateX(10px);
}

/* Certificate preview */
.certificate-preview {
    border: 2px dashed #ddd;
    padding: 3rem;
    text-align: center;
    background: linear-gradient(45deg, #f8f9fa, #e9ecef);
    border-radius: var(--border-radius);
    transition: all var(--transition-speed) ease;
}

.certificate-preview:hover {
    border-color: var(--primary-color);
    background: linear-gradient(45deg, #e9ecef, #f8f9fa);
    transform: scale(1.02);
}

/* Animations */
@keyframes fadeIn {
    from { 
        opacity: 0; 
        transform: translateY(20px); 
    }
    to { 
        opacity: 1; 
        transform: translateY(0); 
    }
}

.fade-in {
    animation: fadeIn 0.6s ease-out;
}

@keyframes pulse {
    0% { transform: scale(1); }
    50% { transform: scale(1.05); }
    100% { transform: scale(1); }
}

.pulse {
    animation: pulse 2s infinite;
}

/* Responsive */
@media (max-width: 768px) {
    .sidebar {
        transform: translateX(-100%);
        width: 280px;
    }
    
    .sidebar.active {
        transform: translateX(0);
    }
    
    .main-content {
        margin-left: 0;
        width: 100%;
        padding: 1rem;
    }
    
    .auth-card {
        margin: 1rem;
        padding: 2rem;
    }
    
    :root {
        --sidebar-width: 0;
    }
}

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

::-webkit-scrollbar-track {
    background: #f1f1f1;
    border-radius: 10px;
}

::-webkit-scrollbar-thumb {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
    border-radius: 10px;
}

::-webkit-scrollbar-thumb:hover {
    background: linear-gradient(135deg, var(--primary-dark), var(--primary-color));
}

/* Loading animation */
.loading {
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 3px solid rgba(255, 255, 255, 0.3);
    border-radius: 50%;
    border-top-color: white;
    animation: spin 1s ease-in-out infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* Success animations */
.success-check {
    color: var(--success-color);
    animation: bounceIn 0.6s ease-out;
}

@keyframes bounceIn {
    0% {
        opacity: 0;
        transform: scale(0.3);
    }
    50% {
        opacity: 1;
        transform: scale(1.05);
    }
    70% {
        transform: scale(0.9);
    }
    100% {
        opacity: 1;
        transform: scale(1);
    }
}

/* Utility classes */
.cursor-pointer {
    cursor: pointer;
}

.hover-lift {
    transition: transform var(--transition-speed) ease;
}

.hover-lift:hover {
    transform: translateY(-3px);
}

.grid-item {
    animation: fadeInUp 0.6s ease-out;
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}