/* ========================================
   AWS SAA-C03 Flashcards - Design System
   ======================================== */

:root {
    /* Color Palette - Dark Theme with AWS Orange */
    --bg-primary: #0a0e17;
    --bg-secondary: #111827;
    --bg-tertiary: #1a2332;
    --bg-card: linear-gradient(145deg, #1a2332 0%, #0f1520 100%);
    
    --accent-primary: #ff9900;
    --accent-secondary: #ffb84d;
    --accent-gradient: linear-gradient(135deg, #ff9900 0%, #ff6600 100%);
    
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    
    --success: #10b981;
    --success-bg: rgba(16, 185, 129, 0.15);
    --warning: #f59e0b;
    --warning-bg: rgba(245, 158, 11, 0.15);
    --info: #3b82f6;
    --info-bg: rgba(59, 130, 246, 0.15);
    
    --border-color: rgba(255, 255, 255, 0.08);
    --border-accent: rgba(255, 153, 0, 0.3);
    
    /* Glassmorphism */
    --glass-bg: rgba(26, 35, 50, 0.7);
    --glass-border: rgba(255, 255, 255, 0.1);
    --glass-shadow: 0 8px 32px rgba(0, 0, 0, 0.4);
    
    /* Typography */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 2rem;
    
    /* Spacing */
    --space-1: 0.25rem;
    --space-2: 0.5rem;
    --space-3: 0.75rem;
    --space-4: 1rem;
    --space-5: 1.25rem;
    --space-6: 1.5rem;
    --space-8: 2rem;
    --space-10: 2.5rem;
    --space-12: 3rem;
    
    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-2xl: 1.5rem;
    --radius-full: 9999px;
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
    --transition-slow: 400ms ease;
    
    /* Sidebar */
    --sidebar-width: 280px;
    --sidebar-collapsed: 0px;
}

/* Reset & Base */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-family);
    background: var(--bg-primary);
    color: var(--text-primary);
    min-height: 100vh;
    overflow-x: hidden;
    background-image: 
        radial-gradient(ellipse at 20% 20%, rgba(255, 153, 0, 0.08) 0%, transparent 50%),
        radial-gradient(ellipse at 80% 80%, rgba(59, 130, 246, 0.06) 0%, transparent 50%);
}

/* App Container */
.app-container {
    display: flex;
    min-height: 100vh;
}

/* ========================================
   Sidebar
   ======================================== */
.sidebar {
    width: var(--sidebar-width);
    background: var(--bg-secondary);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    position: fixed;
    left: 0;
    top: 0;
    bottom: 0;
    z-index: 100;
    transition: transform var(--transition-base);
}

.sidebar-header {
    padding: var(--space-5);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--space-3);
}

.logo-icon {
    font-size: 1.75rem;
}

.logo h1 {
    font-size: var(--font-size-lg);
    font-weight: 700;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.sidebar-toggle {
    display: none;
    width: 32px;
    height: 32px;
    background: transparent;
    border: none;
    cursor: pointer;
    position: relative;
}

.sidebar-toggle span {
    display: block;
    width: 20px;
    height: 2px;
    background: var(--text-secondary);
    position: absolute;
    left: 6px;
    transition: var(--transition-fast);
}

/* Progress Overview */
.progress-overview {
    padding: var(--space-6);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--space-5);
}

.progress-ring-container {
    position: relative;
    width: 100px;
    height: 100px;
}

.progress-ring {
    width: 100%;
    height: 100%;
    transform: rotate(-90deg);
}

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

.progress-ring-fill {
    fill: none;
    stroke: url(#progressGradient);
    stroke-width: 8;
    stroke-linecap: round;
    stroke-dasharray: 283;
    stroke-dashoffset: 283;
    transition: stroke-dashoffset 0.5s ease;
}

.progress-percent {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: var(--font-size-xl);
    font-weight: 700;
    color: var(--accent-primary);
}

.progress-stats {
    display: flex;
    gap: var(--space-6);
    width: 100%;
    justify-content: center;
}

.stat {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--space-1);
}

.stat-value {
    font-size: var(--font-size-xl);
    font-weight: 600;
    color: var(--text-primary);
}

.stat:nth-child(1) .stat-value { color: var(--success); }
.stat:nth-child(2) .stat-value { color: var(--warning); }
.stat:nth-child(3) .stat-value { color: var(--info); }

.stat-label {
    font-size: var(--font-size-xs);
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

/* Category Navigation */
.category-nav {
    flex: 1;
    overflow-y: auto;
    padding: var(--space-4);
}

.nav-section-title {
    font-size: var(--font-size-xs);
    font-weight: 600;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 1px;
    padding: var(--space-2) var(--space-3);
    margin-bottom: var(--space-2);
}

.category-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: var(--space-1);
}

.category-item {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    padding: var(--space-3) var(--space-4);
    border-radius: var(--radius-lg);
    cursor: pointer;
    transition: all var(--transition-fast);
    border: 1px solid transparent;
}

.category-item:hover {
    background: var(--bg-tertiary);
}

.category-item.active {
    background: rgba(255, 153, 0, 0.1);
    border-color: var(--border-accent);
}

.category-icon {
    font-size: 1.1rem;
    width: 24px;
    text-align: center;
}

.category-name {
    flex: 1;
    font-size: var(--font-size-sm);
    font-weight: 500;
    color: var(--text-secondary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.category-item.active .category-name {
    color: var(--accent-primary);
}

.category-count {
    font-size: var(--font-size-xs);
    font-weight: 600;
    color: var(--text-muted);
    background: var(--bg-tertiary);
    padding: var(--space-1) var(--space-2);
    border-radius: var(--radius-full);
    min-width: 28px;
    text-align: center;
}

/* Sidebar Footer */
.sidebar-footer {
    padding: var(--space-4);
    border-top: 1px solid var(--border-color);
}

.reset-btn {
    width: 100%;
    padding: var(--space-3) var(--space-4);
    background: transparent;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    color: var(--text-secondary);
    font-size: var(--font-size-sm);
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-fast);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-2);
}

.reset-btn:hover {
    background: rgba(239, 68, 68, 0.1);
    border-color: rgba(239, 68, 68, 0.3);
    color: #ef4444;
}

/* ========================================
   Main Content
   ======================================== */
.main-content {
    flex: 1;
    margin-left: var(--sidebar-width);
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

/* Main Header */
.main-header {
    padding: var(--space-5) var(--space-8);
    display: flex;
    align-items: center;
    justify-content: space-between;
    border-bottom: 1px solid var(--border-color);
    background: rgba(17, 24, 39, 0.8);
    backdrop-filter: blur(10px);
    position: sticky;
    top: 0;
    z-index: 50;
}

.header-left {
    display: flex;
    align-items: center;
    gap: var(--space-4);
}

.mobile-menu-btn {
    display: none;
    width: 40px;
    height: 40px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    cursor: pointer;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 4px;
}

.mobile-menu-btn span {
    display: block;
    width: 18px;
    height: 2px;
    background: var(--text-secondary);
    border-radius: 1px;
}

.current-category {
    display: flex;
    align-items: center;
    gap: var(--space-3);
}

.current-category span {
    font-size: 1.5rem;
}

.current-category h2 {
    font-size: var(--font-size-xl);
    font-weight: 600;
}

.header-right {
    display: flex;
    align-items: center;
    gap: var(--space-6);
}

.card-counter {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    font-size: var(--font-size-lg);
    font-weight: 600;
}

.card-counter .separator {
    color: var(--text-muted);
}

#currentCardNum {
    color: var(--accent-primary);
}

.view-controls {
    display: flex;
    gap: var(--space-2);
}

.control-btn {
    width: 44px;
    height: 44px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    color: var(--text-secondary);
    font-size: 1.25rem;
    cursor: pointer;
    transition: all var(--transition-fast);
    display: flex;
    align-items: center;
    justify-content: center;
}

.control-btn:hover {
    background: rgba(255, 153, 0, 0.1);
    border-color: var(--border-accent);
    color: var(--accent-primary);
}

/* Filter Dropdown */
.filter-dropdown {
    position: absolute;
    top: 70px;
    right: var(--space-8);
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--space-2);
    display: none;
    flex-direction: column;
    z-index: 60;
    box-shadow: var(--glass-shadow);
}

.filter-dropdown.show {
    display: flex;
}

.filter-option {
    padding: var(--space-3) var(--space-4);
    background: transparent;
    border: none;
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    font-size: var(--font-size-sm);
    font-weight: 500;
    cursor: pointer;
    text-align: left;
    transition: all var(--transition-fast);
}

.filter-option:hover {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.filter-option.active {
    background: rgba(255, 153, 0, 0.1);
    color: var(--accent-primary);
}

/* ========================================
   Flashcard Container
   ======================================== */
.flashcard-container {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: var(--space-8);
    gap: var(--space-6);
    position: relative;
}

/* Navigation Arrows */
.nav-arrow {
    width: 56px;
    height: 56px;
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-full);
    cursor: pointer;
    transition: all var(--transition-fast);
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.nav-arrow svg {
    width: 28px;
    height: 28px;
    fill: var(--text-secondary);
    transition: fill var(--transition-fast);
}

.nav-arrow:hover {
    background: rgba(255, 153, 0, 0.15);
    border-color: var(--border-accent);
    transform: scale(1.05);
}

.nav-arrow:hover svg {
    fill: var(--accent-primary);
}

.nav-arrow:active {
    transform: scale(0.95);
}

/* Flashcard Wrapper */
.flashcard-wrapper {
    perspective: 1500px;
    width: 100%;
    max-width: 700px;
}

/* Flashcard */
.flashcard {
    width: 100%;
    height: 420px;
    cursor: pointer;
    position: relative;
}

.flashcard-inner {
    width: 100%;
    height: 100%;
    position: relative;
    transform-style: preserve-3d;
    transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
}

.flashcard.flipped .flashcard-inner {
    transform: rotateY(180deg);
}

.flashcard-front,
.flashcard-back {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    border-radius: var(--radius-2xl);
    padding: var(--space-8);
    display: flex;
    flex-direction: column;
    border: 1px solid var(--glass-border);
    box-shadow: var(--glass-shadow);
    overflow: hidden;
}

.flashcard-front {
    background: var(--bg-card);
}

.flashcard-front::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--accent-gradient);
}

.flashcard-back {
    background: linear-gradient(145deg, #1e293b 0%, #0f172a 100%);
    transform: rotateY(180deg);
}

.flashcard-back::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: linear-gradient(135deg, var(--success) 0%, #059669 100%);
}

/* Card Content */
.card-service-tag {
    display: inline-flex;
    align-self: flex-start;
    padding: var(--space-2) var(--space-4);
    background: rgba(255, 153, 0, 0.15);
    border: 1px solid rgba(255, 153, 0, 0.3);
    border-radius: var(--radius-full);
    font-size: var(--font-size-sm);
    font-weight: 600;
    color: var(--accent-primary);
    margin-bottom: var(--space-6);
}

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

.scenario-label,
.answer-label {
    font-size: var(--font-size-xs);
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 1.5px;
    margin-bottom: var(--space-4);
}

.scenario-label {
    color: var(--accent-secondary);
}

.answer-label {
    color: var(--success);
}

.scenario-text {
    font-size: var(--font-size-lg);
    line-height: 1.7;
    color: var(--text-primary);
    flex: 1;
}

.answer-title {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    color: var(--success);
    margin-bottom: var(--space-4);
}

.answer-details {
    font-size: var(--font-size-base);
    line-height: 1.8;
    color: var(--text-secondary);
    flex: 1;
    overflow-y: auto;
}

.answer-details ul {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: var(--space-2);
}

.answer-details li {
    display: flex;
    align-items: flex-start;
    gap: var(--space-2);
}

.answer-details li::before {
    content: '✓';
    color: var(--success);
    font-weight: 600;
    flex-shrink: 0;
}

.card-hint {
    text-align: center;
    padding-top: var(--space-4);
    border-top: 1px solid var(--border-color);
    margin-top: auto;
}

.card-hint span {
    font-size: var(--font-size-sm);
    color: var(--text-muted);
}

/* Card Actions */
.card-actions {
    display: flex;
    gap: var(--space-4);
    padding-top: var(--space-4);
    border-top: 1px solid var(--border-color);
    margin-top: auto;
}

.action-btn {
    flex: 1;
    padding: var(--space-3) var(--space-4);
    border-radius: var(--radius-lg);
    font-size: var(--font-size-sm);
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-2);
    border: 1px solid transparent;
}

.action-btn.needs-review {
    background: var(--warning-bg);
    border-color: rgba(245, 158, 11, 0.3);
    color: var(--warning);
}

.action-btn.needs-review:hover {
    background: rgba(245, 158, 11, 0.25);
    transform: translateY(-2px);
}

.action-btn.mastered {
    background: var(--success-bg);
    border-color: rgba(16, 185, 129, 0.3);
    color: var(--success);
}

.action-btn.mastered:hover {
    background: rgba(16, 185, 129, 0.25);
    transform: translateY(-2px);
}

/* ========================================
   Shortcuts Bar
   ======================================== */
.shortcuts-bar {
    display: flex;
    justify-content: center;
    gap: var(--space-8);
    padding: var(--space-5);
    background: var(--bg-secondary);
    border-top: 1px solid var(--border-color);
}

.shortcut {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    color: var(--text-muted);
    font-size: var(--font-size-sm);
}

kbd {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-width: 28px;
    height: 28px;
    padding: 0 var(--space-2);
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-family: inherit;
    font-size: var(--font-size-xs);
    font-weight: 600;
    color: var(--text-secondary);
}

/* ========================================
   Responsive Design
   ======================================== */
@media (max-width: 1024px) {
    .flashcard {
        height: 380px;
    }
    
    .flashcard-front,
    .flashcard-back {
        padding: var(--space-6);
    }
}

@media (max-width: 768px) {
    .sidebar {
        transform: translateX(-100%);
    }
    
    .sidebar.open {
        transform: translateX(0);
    }
    
    .main-content {
        margin-left: 0;
    }
    
    .mobile-menu-btn {
        display: flex;
    }
    
    .main-header {
        padding: var(--space-4);
    }
    
    .flashcard-container {
        padding: var(--space-4);
        flex-direction: column;
    }
    
    .nav-arrow {
        display: none;
    }
    
    .flashcard {
        height: 450px;
    }
    
    .flashcard-wrapper {
        max-width: 100%;
    }
    
    .shortcuts-bar {
        display: none;
    }
    
    .header-right {
        gap: var(--space-3);
    }
    
    .card-counter {
        font-size: var(--font-size-base);
    }
    
    .control-btn {
        width: 40px;
        height: 40px;
    }
}

@media (max-width: 480px) {
    .current-category h2 {
        font-size: var(--font-size-base);
    }
    
    .flashcard {
        height: 480px;
    }
    
    .scenario-text {
        font-size: var(--font-size-base);
    }
    
    .answer-title {
        font-size: var(--font-size-xl);
    }
}

/* Overlay for mobile */
.sidebar-overlay {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    z-index: 99;
}

.sidebar-overlay.show {
    display: block;
}

/* Touch swipe hint */
@media (max-width: 768px) {
    .flashcard-container::after {
        content: 'Swipe left/right to navigate';
        position: absolute;
        bottom: var(--space-4);
        left: 50%;
        transform: translateX(-50%);
        font-size: var(--font-size-sm);
        color: var(--text-muted);
        opacity: 0.7;
    }
}

/* Status indicators on cards */
.flashcard[data-status="mastered"]::after {
    content: '✓ Mastered';
    position: absolute;
    top: var(--space-4);
    right: var(--space-4);
    padding: var(--space-1) var(--space-3);
    background: var(--success-bg);
    border: 1px solid rgba(16, 185, 129, 0.3);
    border-radius: var(--radius-full);
    font-size: var(--font-size-xs);
    font-weight: 600;
    color: var(--success);
    z-index: 10;
}

.flashcard[data-status="review"]::after {
    content: '↻ Review';
    position: absolute;
    top: var(--space-4);
    right: var(--space-4);
    padding: var(--space-1) var(--space-3);
    background: var(--warning-bg);
    border: 1px solid rgba(245, 158, 11, 0.3);
    border-radius: var(--radius-full);
    font-size: var(--font-size-xs);
    font-weight: 600;
    color: var(--warning);
    z-index: 10;
}

/* Custom scrollbar */
::-webkit-scrollbar {
    width: 6px;
    height: 6px;
}

::-webkit-scrollbar-track {
    background: var(--bg-tertiary);
}

::-webkit-scrollbar-thumb {
    background: var(--text-muted);
    border-radius: 3px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--text-secondary);
}

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

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.6; }
}

.flashcard {
    animation: fadeIn 0.3s ease;
}

/* Loading state */
.loading {
    animation: pulse 1.5s infinite;
}