:root {
    /* Brand Colors */
    --primary-bg: #9CEDEF;
    --primary-blue: #3b82f6;
    --primary-green: #10b981;
    --primary-orange: #f59e0b;
    --primary-purple: #8b5cf6;
    --primary-red: #ef4444;
    --primary-pink: #ec4899;
    
    /* Neutral Colors */
    --white: #ffffff;
    --black: #000000;
    --gray-50: #f9fafb;
    --gray-100: #f3f4f6;
    --gray-200: #e5e7eb;
    --gray-300: #d1d5db;
    --gray-400: #9ca3af;
    --gray-500: #6b7280;
    --gray-600: #4b5563;
    --gray-700: #374151;
    --gray-800: #1f2937;
    --gray-900: #111827;
    
    /* Semantic Colors */
    --success: #10b981;
    --warning: #f59e0b;
    --error: #ef4444;
    --info: #3b82f6;
    
    /* Typography */
    --font-heading: 'Exo 2', 'Bebas Neue', sans-serif;
    --font-body: 'Manrope', sans-serif;
    --font-small: 'Inter', sans-serif;
    
    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    --spacing-3xl: 4rem;
    
    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-2xl: 1.5rem;
    --radius-full: 9999px;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-normal: 300ms ease;
    --transition-slow: 500ms ease;

    /* Card & Text (used by internal pages) */
    --card-bg: #ffffff;
    --card-border: #e5e7eb;
    --text-primary: #111827;
    --text-secondary: #6b7280;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-body);
    background-color: var(--primary-bg);
    color: var(--gray-900);
    line-height: 1.6;
    overflow-x: hidden;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-heading);
    font-weight: 800;
    line-height: 1.2;
    color: var(--gray-900);
}

h1 {
    font-size: clamp(2rem, 5vw, 3.5rem);
}

h2 {
    font-size: clamp(1.75rem, 4vw, 2.5rem);
}

h3 {
    font-size: clamp(1.25rem, 3vw, 1.875rem);
}

h4 {
    font-size: 1.25rem;
}

p {
    font-family: var(--font-body);
    font-size: 1rem;
    color: var(--gray-700);
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: var(--radius-full);
    font-family: var(--font-body);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: transform var(--transition-fast), box-shadow var(--transition-fast), background-color var(--transition-fast);
    text-decoration: none;
}

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

.btn:active {
    transform: translateY(0);
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-blue) 0%, var(--primary-purple) 100%);
    color: var(--white);
}

.btn-primary:hover {
    background: linear-gradient(135deg, #2563eb 0%, #7c3aed 100%);
}

.btn-secondary {
    background-color: var(--white);
    color: var(--gray-900);
    border: 2px solid var(--gray-200);
}

.btn-secondary:hover {
    background-color: var(--gray-50);
    border-color: var(--gray-300);
}

.btn-outline {
    background-color: transparent;
    color: var(--gray-900);
    border: 2px solid var(--gray-900);
}

.btn-outline:hover {
    background-color: var(--gray-900);
    color: var(--white);
}

.btn-large {
    padding: 1rem 2rem;
    font-size: 1.125rem;
}

.btn-small {
    padding: 0.5rem 1rem;
    font-size: 0.875rem;
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none;
}

/* Container */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1.5rem;
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.6);
    backdrop-filter: blur(8px);
    z-index: 1000;
    align-items: center;
    justify-content: center;
    animation: fadeIn var(--transition-normal);
}

.modal.active {
    display: flex;
}

.modal-content {
    background-color: var(--white);
    border-radius: var(--radius-2xl);
    padding: 2.5rem;
    max-width: 450px;
    width: 90%;
    position: relative;
    box-shadow: var(--shadow-xl);
    animation: slideUp var(--transition-normal);
}

.modal-close {
    position: absolute;
    top: 1rem;
    right: 1rem;
    background: none;
    border: none;
    font-size: 2rem;
    color: var(--gray-400);
    cursor: pointer;
    transition: color var(--transition-fast);
    line-height: 1;
}

.modal-close:hover {
    color: var(--gray-900);
}

/* Auth Forms */
.auth-form {
    display: none;
}

.auth-form.active {
    display: block;
    animation: fadeIn var(--transition-normal);
}

.auth-mascot {
    text-align: center;
    margin-bottom: 1.5rem;
}

.auth-mascot img {
    width: 120px;
    height: 120px;
    object-fit: contain;
    animation: bounce 2s infinite;
}

.auth-form h2 {
    text-align: center;
    margin-bottom: 0.5rem;
    color: var(--gray-900);
}

.auth-subtitle {
    text-align: center;
    color: var(--gray-600);
    margin-bottom: 2rem;
    font-size: 0.95rem;
}

.input-group {
    margin-bottom: 1rem;
}

.input-group input {
    width: 100%;
    padding: 0.875rem 1rem;
    border: 2px solid var(--gray-200);
    border-radius: var(--radius-lg);
    font-family: var(--font-body);
    font-size: 1rem;
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.input-group input:focus {
    outline: none;
    border-color: var(--primary-blue);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.auth-form button[type="submit"] {
    width: 100%;
    margin-top: 1rem;
}

.auth-footer {
    text-align: center;
    margin-top: 1.5rem;
    font-size: 0.95rem;
    color: var(--gray-600);
}

.auth-footer a {
    color: var(--primary-blue);
    text-decoration: none;
    font-weight: 600;
    transition: color var(--transition-fast);
}

.auth-footer a:hover {
    color: var(--primary-purple);
}

/* Sidebar */
.sidebar {
    position: fixed;
    left: 0;
    top: 0;
    width: 280px;
    height: 100vh;
    background-color: var(--white);
    box-shadow: var(--shadow-lg);
    display: flex;
    flex-direction: column;
    z-index: 100;
    transition: transform var(--transition-normal);
}

.sidebar-header {
    padding: 2rem 1.5rem;
    border-bottom: 2px solid var(--gray-100);
}

.sidebar-logo {
    width: 60px;
    height: 60px;
    object-fit: contain;
}

.sidebar-nav {
    flex: 1;
    padding: 1rem 0;
    overflow-y: auto;
}

.sidebar-link {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 0.875rem 1.5rem;
    color: var(--gray-700);
    text-decoration: none;
    font-weight: 500;
    transition: background-color var(--transition-fast), color var(--transition-fast);
    border: none;
    background: none;
    width: 100%;
    text-align: left;
    cursor: pointer;
}

.sidebar-link i {
    font-size: 1.25rem;
    width: 24px;
    text-align: center;
}

.sidebar-link:hover {
    background-color: var(--gray-100);
    color: var(--gray-900);
}

.sidebar-link.active {
    background-color: var(--primary-blue);
    color: var(--white);
    font-weight: 600;
}

.sidebar-footer {
    padding: 1rem;
    border-top: 2px solid var(--gray-100);
}

.logout-btn {
    color: var(--primary-red);
}

.logout-btn:hover {
    background-color: rgba(239, 68, 68, 0.1);
    color: var(--primary-red);
}

/* Main Content */
.main-content {
    margin-left: 280px;
    min-height: 100vh;
    padding-bottom: 2rem;
}

/* Topbar */
.topbar {
    background-color: var(--white);
    padding: 1.25rem 2rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 50;
}

.mobile-menu-btn {
    display: none;
    background: none;
    border: none;
    font-size: 1.5rem;
    color: var(--gray-700);
    cursor: pointer;
}

.page-title {
    font-size: 1.75rem;
    font-weight: 800;
    color: var(--gray-900);
}

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

.xp-badge {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    background: linear-gradient(135deg, #fbbf24 0%, #f59e0b 100%);
    color: var(--white);
    padding: 0.5rem 1rem;
    border-radius: var(--radius-full);
    font-weight: 700;
    font-size: 0.95rem;
    box-shadow: var(--shadow-md);
}

.notification-btn {
    position: relative;
    background: none;
    border: none;
    font-size: 1.25rem;
    color: var(--gray-700);
    cursor: pointer;
    transition: color var(--transition-fast);
}

.notification-btn:hover {
    color: var(--gray-900);
}

.notification-dot {
    position: absolute;
    top: 0;
    right: 0;
    width: 8px;
    height: 8px;
    background-color: var(--primary-red);
    border-radius: 50%;
    animation: pulse 2s infinite;
}

/* Animations */
@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

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

@keyframes bounce {
    0%, 100% {
        transform: translateY(0);
    }
    50% {
        transform: translateY(-10px);
    }
}

@keyframes pulse {
    0%, 100% {
        opacity: 1;
    }
    50% {
        opacity: 0.5;
    }
}

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

/* Responsive Design */
@media (max-width: 1024px) {
    .sidebar {
        transform: translateX(-100%);
    }
    
    .sidebar.active {
        transform: translateX(0);
    }
    
    .main-content {
        margin-left: 0;
    }
    
    .mobile-menu-btn {
        display: block;
    }
}

@media (max-width: 768px) {
    .container {
        padding: 0 1rem;
    }
    
    .topbar {
        padding: 1rem 1.5rem;
    }
    
    .page-title {
        font-size: 1.5rem;
    }
    
    .modal-content {
        padding: 2rem 1.5rem;
    }
    
    .btn-large {
        padding: 0.875rem 1.5rem;
        font-size: 1rem;
    }
}

@media (max-width: 480px) {
    .topbar {
        padding: 1rem;
    }
    
    .page-title {
        font-size: 1.25rem;
    }
    
    .xp-badge {
        padding: 0.4rem 0.75rem;
        font-size: 0.85rem;
    }
}

/* ============================================
   DARK THEME - Internal Pages Only
   Applied via data-theme="dark" on <html>
   Theme toggle is NOT included on landing page
   ============================================ */

[data-theme="dark"] {
    --primary-bg: #0f172a;
    --white: #1e293b;
    --black: #f1f5f9;
    --gray-50: #1e293b;
    --gray-100: #263447;
    --gray-200: #334155;
    --gray-300: #475569;
    --gray-400: #64748b;
    --gray-500: #94a3b8;
    --gray-600: #cbd5e1;
    --gray-700: #e2e8f0;
    --gray-800: #f1f5f9;
    --gray-900: #f8fafc;

    --card-bg: #1e293b;
    --card-border: #334155;
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;

    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.2);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.3);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.3);
}

[data-theme="dark"] body {
    background-color: #0f172a;
    color: #f8fafc;
}

[data-theme="dark"] .sidebar {
    background-color: #1e293b;
    box-shadow: 2px 0 8px rgba(0,0,0,0.3);
}

[data-theme="dark"] .sidebar-header {
    border-bottom-color: #334155;
}

[data-theme="dark"] .sidebar-footer {
    border-top-color: #334155;
}

[data-theme="dark"] .sidebar-link:hover {
    background-color: #263447;
}

[data-theme="dark"] .topbar {
    background-color: #1e293b;
    box-shadow: 0 1px 3px rgba(0,0,0,0.3);
}

[data-theme="dark"] .input-group input {
    background-color: #263447;
    border-color: #334155;
    color: #f8fafc;
}

[data-theme="dark"] .modal-content {
    background-color: #1e293b;
}

/* Theme Toggle Button */
.theme-toggle-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    border: 2px solid var(--gray-200);
    background: var(--white);
    color: var(--gray-700);
    cursor: pointer;
    font-size: 1rem;
    transition: all var(--transition-fast);
}

.theme-toggle-btn:hover {
    border-color: var(--primary-blue);
    color: var(--primary-blue);
    transform: rotate(20deg);
}

/* ============================================
   Lesson Reader Modal (Chapters)
   ============================================ */
.lesson-modal {
    display: none;
    position: fixed;
    top: 0; left: 0;
    width: 100%; height: 100%;
    background-color: rgba(0,0,0,0.7);
    backdrop-filter: blur(8px);
    z-index: 2000;
    align-items: center;
    justify-content: center;
    padding: 1rem;
}

.lesson-modal.active { display: flex; }

.lesson-modal-content {
    background-color: var(--white);
    border-radius: var(--radius-2xl);
    width: 100%; max-width: 800px; max-height: 90vh;
    overflow-y: auto;
    box-shadow: var(--shadow-xl);
    animation: slideUp 0.3s ease;
}

.lesson-modal-header {
    padding: 1.5rem 2rem;
    border-bottom: 2px solid var(--gray-200);
    display: flex; justify-content: space-between; align-items: center;
    position: sticky; top: 0;
    background-color: var(--white);
    z-index: 10;
}

.lesson-modal-header h3 {
    color: var(--gray-900);
    font-size: 1.5rem;
}

.lesson-modal-close {
    background: none; border: none;
    font-size: 1.75rem;
    color: var(--gray-400);
    cursor: pointer;
}

.lesson-modal-body { padding: 2rem; }

.lesson-modal-body h4 {
    font-size: 1.25rem;
    color: var(--gray-900);
    margin-bottom: 1rem;
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--primary-blue);
}

.lesson-modal-body p {
    color: var(--gray-600);
    line-height: 1.8;
    margin-bottom: 1rem;
}

.lesson-code-block {
    background-color: #1e293b;
    color: #e2e8f0;
    padding: 1.5rem;
    border-radius: var(--radius-lg);
    font-family: 'Courier New', monospace;
    font-size: 0.9rem;
    overflow-x: auto;
    line-height: 1.7;
    margin-bottom: 1rem;
}

[data-theme="dark"] .lesson-code-block {
    background-color: #0f172a;
    border: 1px solid #334155;
}

.lesson-tip {
    background: linear-gradient(135deg, rgba(59,130,246,0.1), rgba(139,92,246,0.1));
    border-left: 4px solid var(--primary-blue);
    padding: 1rem 1.5rem;
    border-radius: 0 var(--radius-lg) var(--radius-lg) 0;
    margin-bottom: 1rem;
}

.lesson-tip strong { color: var(--primary-blue); }

.lesson-modal-footer {
    padding: 1.5rem 2rem;
    border-top: 2px solid var(--gray-200);
    display: flex; justify-content: flex-end; gap: 1rem;
}

.lesson-completed-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--success);
    font-weight: 600;
    font-size: 0.9rem;
}

.lesson-reread-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
    color: var(--primary-blue);
    font-size: 0.85rem;
    font-weight: 600;
    padding: 0.25rem 0.75rem;
    background: rgba(59,130,246,0.1);
    border-radius: var(--radius-full);
}

.lesson-start-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
    color: var(--primary-green);
    font-size: 0.85rem;
    font-weight: 600;
    padding: 0.25rem 0.75rem;
    background: rgba(16,185,129,0.1);
    border-radius: var(--radius-full);
}

/* ============================================
   Hint Banner (Quiz failed - links to chapters)
   ============================================ */
.hint-banner {
    background: linear-gradient(135deg, rgba(245,158,11,0.15), rgba(251,191,36,0.15));
    border: 2px solid #fbbf24;
    border-radius: var(--radius-xl);
    padding: 1.25rem 1.5rem;
    display: flex; align-items: center; gap: 1rem;
    margin-bottom: 1.5rem;
}

.hint-banner i { color: #fbbf24; font-size: 1.5rem; flex-shrink: 0; }
.hint-banner p { color: var(--gray-900); font-weight: 600; margin: 0; }
.hint-banner a { color: var(--primary-blue); text-decoration: underline; font-weight: 700; }

/* Quiz Pass/Fail Status */
.result-status-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius-full);
    font-weight: 700;
    font-size: 1.1rem;
    margin-bottom: 1rem;
}

.result-status-badge.passed {
    background: rgba(16,185,129,0.15);
    color: var(--primary-green);
}

.result-status-badge.failed {
    background: rgba(239,68,68,0.15);
    color: var(--primary-red);
}

/* ============================================
   Quiz History List
   ============================================ */
.quiz-history-section { margin-top: 1.5rem; }

.quiz-history-item {
    display: flex; align-items: center; justify-content: space-between;
    padding: 1rem 1.25rem;
    background-color: var(--gray-50);
    border-radius: var(--radius-lg);
    border: 2px solid var(--gray-200);
    margin-bottom: 0.75rem;
    transition: transform var(--transition-fast);
}

.quiz-history-item:hover { transform: translateX(4px); }

.history-badge {
    font-size: 0.75rem;
    font-weight: 700;
    padding: 0.3rem 0.75rem;
    border-radius: var(--radius-full);
}

.history-badge.passed { background: rgba(16,185,129,0.15); color: var(--primary-green); }
.history-badge.failed { background: rgba(239,68,68,0.15); color: var(--primary-red); }

/* ============================================
   Notifications Toast
   ============================================ */
.notification {
    position: fixed; top: 20px; right: 20px;
    padding: 1rem 1.5rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    z-index: 9999;
    animation: slideUp 0.3s ease;
    font-weight: 600;
    color: #fff;
}

.notification-success { background: var(--success); }
.notification-error { background: var(--error); }
.notification-info { background: var(--info); }