:root {
    /* Main Branding */
    --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --primary-color: #667eea;
    --secondary-color: #764ba2;
    --success-color: #10b981;
    --danger-color: #ef4444;
    --warning-color: #f59e0b;
    
    /* Light Mode Surface Colors */
    --body-bg: linear-gradient(180deg, #f8fafc 0%, #eef2ff 100%);
    --card-bg: rgba(255, 255, 255, 0.9);
    --feature-card-bg: white;
    --text-main: #1f2937;
    --text-muted: #6b7280;
    --nav-bg: rgba(255, 255, 255, 0.9);
    --input-bg: white;
    --border-color: rgba(0, 0, 0, 0.08);
    --accordion-bg: white;
    
    /* Shadows & Effects */
    --card-shadow: 0 10px 40px rgba(0, 0, 0, 0.08);
    --hover-shadow: 0 20px 60px rgba(0, 0, 0, 0.12);
    --border-radius-lg: 20px;
    --border-radius-md: 16px;
    --border-radius-sm: 12px;
    --transition-smooth: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

[data-theme="dark"] {
    /* Dark Mode Surface Colors */
    --body-bg: linear-gradient(180deg, #0f172a 0%, #1e293b 100%);
    --card-bg: rgba(30, 41, 59, 0.7);
    --feature-card-bg: #1e293b;
    --text-main: #f1f5f9;
    --text-muted: #94a3b8;
    --nav-bg: rgba(15, 23, 42, 0.9);
    --input-bg: #0f172a;
    --border-color: rgba(255, 255, 255, 0.1);
    --accordion-bg: #1e293b;
    
    /* Dark Mode Shadows */
    --card-shadow: 0 10px 40px rgba(0, 0, 0, 0.3);
    --hover-shadow: 0 20px 60px rgba(0, 0, 0, 0.4);
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: var(--body-bg) !important;
    color: var(--text-main);
    min-height: 100vh;
    transition: background-color 0.4s ease;
}

/* Modern Course Cards */
.course-card {
    transition: var(--transition-smooth);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    overflow: hidden;
    background: var(--card-bg) !important;
    backdrop-filter: blur(10px);
    box-shadow: var(--card-shadow);
    animation: cardAppear 0.5s ease-out forwards;
    opacity: 0;
}

.course-card .card-body { padding: 1.5rem; }

.course-card .card-title {
    font-weight: 700;
    font-size: 1.25rem;
    color: var(--text-main);
    margin-bottom: 0.5rem;
}

.card-text.text-muted, .text-muted {
    color: var(--text-muted) !important;
}

/* Hero Section */
.hero-section {
    background: var(--primary-gradient);
    border-radius: var(--border-radius-lg);
    padding: 4rem 2rem;
    position: relative;
    overflow: hidden;
    color: white; /* Always white on gradient */
}

/* Feature Cards */
.feature-card {
    background: var(--feature-card-bg);
    color: var(--text-main);
    border-radius: var(--border-radius-md);
    padding: 2rem;
    box-shadow: var(--card-shadow);
    transition: var(--transition-smooth);
    border: 1px solid var(--border-color);
    backdrop-filter: blur(10px);
}

/* Module Accordion */
.accordion-item {
    border: none;
    margin-bottom: 1rem;
    background-color: transparent !important;
    border-radius: var(--border-radius-sm) !important;
    overflow: hidden;
}

.accordion-button {
    background-color: var(--accordion-bg) !important;
    color: var(--text-main) !important;
    border: 1px solid var(--border-color);
    font-weight: 600;
}

.accordion-button:not(.collapsed) {
    background: var(--primary-gradient) !important;
    color: white !important;
    border-color: transparent;
}

.accordion-button::after {
    filter: invert(var(--dark-mode-toggle, 0)); /* Flips arrow color in dark mode if needed */
}

[data-theme="dark"] .accordion-button::after {
    filter: invert(1) brightness(2);
}

/* Dashboard Stats Cards */
.stat-card {
    background: var(--feature-card-bg);
    color: var(--text-main);
    border-radius: var(--border-radius-md);
    padding: 1.5rem;
    box-shadow: var(--card-shadow);
    border: 1px solid var(--border-color);
}

/* Resource Items */
.resource-item {
    padding: 1rem 1.25rem;
    margin: 0.5rem 0;
    border-radius: var(--border-radius-sm);
    background: var(--input-bg);
    color: var(--text-main);
    border: 1px solid var(--border-color);
}

.resource-item:hover {
    background: var(--primary-gradient);
    color: white;
    transform: translateX(5px);
}

/* Tables */
.table {
    color: var(--text-main) !important;
    background-color: var(--card-bg);
}

.table tbody tr:hover {
    background: rgba(102, 126, 234, 0.1);
    color: var(--text-main);
}

.table td, .table th {
    border-color: var(--border-color);
}

/* Forms */
.form-control, .form-select {
    border-radius: 12px;
    border: 2px solid var(--border-color);
    padding: 0.75rem 1rem;
    background-color: var(--input-bg) !important;
    color: var(--text-main) !important;
    transition: var(--transition-smooth);
}

.form-control::placeholder {
    color: var(--text-muted);
}

/* Navigation Bar */
.navbar {
    backdrop-filter: blur(15px);
    background: var(--nav-bg) !important;
    border-bottom: 1px solid var(--border-color);
}

.nav-link {
    color: var(--text-main) !important;
}

/* Dropdowns */
.dropdown-menu {
    background-color: var(--feature-card-bg);
    border: 1px solid var(--border-color);
    box-shadow: var(--card-shadow);
}

.dropdown-item {
    color: var(--text-main);
}

.dropdown-item:hover {
    background: var(--primary-gradient);
    color: white;
}

/* Modals */
.modal-content {
    background-color: var(--feature-card-bg);
    color: var(--text-main);
    border: 1px solid var(--border-color);
    border-radius: 24px;
}

.btn-close {
    filter: invert(var(--dark-mode-toggle, 0));
}

[data-theme="dark"] .btn-close {
    filter: invert(1) brightness(2);
}

/* Payment Success Context */
.payment-success-wrapper {
    height: 70vh;
    display: flex;
    justify-content: center;
    align-items: center;
    background: rgba(30, 41, 59, 0.93);
    border-radius: 20px;
    position: relative;
}

.glass-card {
    backdrop-filter: blur(20px);
    background: rgba(30, 41, 59, 0.93);
    border-radius: 20px;
    padding: 50px;
    text-align: center;
    color: white;
    box-shadow: 0 20px 60px rgba(0,0,0,0.1);
    z-index: 10;
}

.confetti-piece {
    position: fixed;
    width: 10px;
    height: 10px;
    top: -10px;
    z-index: 9999;
    pointer-events: none;
    animation: fall linear forwards;
}

@keyframes fall {
    to { transform: translateY(105vh) rotate(720deg); opacity: 0; }
}

/* Pagination */
.page-link {
    background-color: var(--input-bg);
    color: var(--text-main);
    border-color: var(--border-color);
}

/* Animations (existing logic preserved) */
@keyframes cardAppear { from { opacity: 0; transform: translateY(30px); } to { opacity: 1; transform: translateY(0); } }