/* ==================== CSS Variables ==================== */
:root {
    /* Colors - Light Theme */
    --primary: #667eea;
    --primary-dark: #5568d3;
    --primary-light: #7c8ef0;
    --secondary: #764ba2;
    --accent: #f093fb;
    
    --bg-primary: #ffffff;
    --bg-secondary: #f8f9fa;
    --bg-tertiary: #e9ecef;
    --bg-elevated: #ffffff;
    
    --text-primary: #1a202c;
    --text-secondary: #4a5568;
    --text-tertiary: #718096;
    
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.07);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 40px rgba(0, 0, 0, 0.15);
    
    --success: #48bb78;
    --error: #f56565;
    --warning: #ed8936;
    
    /* Gradients */
    --gradient-primary: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --gradient-secondary: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    --gradient-success: linear-gradient(135deg, #48bb78 0%, #38a169 100%);
    
    /* Typography */
    --font-primary: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-mono: 'JetBrains Mono', 'Courier New', monospace;
    
    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    
    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-2xl: 1.5rem;
    
    /* Transitions */
    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 350ms cubic-bezier(0.4, 0, 0.2, 1);
}

/* Dark Theme */
[data-theme="dark"] {
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;
    --bg-elevated: #1e293b;
    
    --text-primary: #f1f5f9;
    --text-secondary: #cbd5e1;
    --text-tertiary: #94a3b8;
    
    --border-color: #334155;
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.5);
    --shadow-xl: 0 20px 40px rgba(0, 0, 0, 0.6);
}

/* ==================== Reset & Base Styles ==================== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-primary);
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    transition: background-color var(--transition-base), color var(--transition-base);
}

/* ==================== Navigation ==================== */
.navbar {
    background: var(--bg-elevated);
    border-bottom: 1px solid var(--border-color);
    padding: var(--spacing-md) 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    backdrop-filter: blur(10px);
    box-shadow: var(--shadow-sm);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: 1.5rem;
    font-weight: 700;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: var(--spacing-sm);
}

.nav-link {
    padding: var(--spacing-sm) var(--spacing-md);
    color: var(--text-secondary);
    text-decoration: none;
    border-radius: var(--radius-md);
    font-weight: 500;
    transition: all var(--transition-fast);
    position: relative;
}

.nav-link:hover {
    color: var(--primary);
    background: var(--bg-secondary);
}

.nav-link.active {
    color: var(--primary);
    background: var(--bg-secondary);
}

.theme-toggle {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-sm);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-fast);
    color: var(--text-primary);
}

.theme-toggle:hover {
    background: var(--bg-tertiary);
    transform: scale(1.05);
}

.moon-icon {
    display: none;
}

[data-theme="dark"] .sun-icon {
    display: none;
}

[data-theme="dark"] .moon-icon {
    display: block;
}

/* ==================== Container & Layout ==================== */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-2xl) var(--spacing-lg);
}

.page {
    display: none;
}

.page.active {
    display: block;
    animation: fadeIn var(--transition-base);
}

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

/* ==================== Hero Section ==================== */
.hero {
    text-align: center;
    margin-bottom: var(--spacing-2xl);
}

.hero h1 {
    font-size: 2.5rem;
    font-weight: 800;
    margin-bottom: var(--spacing-md);
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.subtitle {
    font-size: 1.125rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
}

/* ==================== Config Panel ==================== */
.config-panel {
    background: var(--bg-elevated);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    padding: var(--spacing-xl);
    margin-bottom: var(--spacing-xl);
    display: flex;
    gap: var(--spacing-2xl);
    justify-content: center;
    flex-wrap: wrap;
    box-shadow: var(--shadow-md);
}

.config-group {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.config-group label {
    font-weight: 600;
    color: var(--text-secondary);
    font-size: 0.875rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.button-group {
    display: flex;
    gap: var(--spacing-sm);
}

.config-btn {
    padding: var(--spacing-sm) var(--spacing-lg);
    background: var(--bg-secondary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    color: var(--text-primary);
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
    font-family: var(--font-primary);
    font-size: 0.9375rem;
}

.config-btn:hover {
    background: var(--bg-tertiary);
    transform: translateY(-2px);
    box-shadow: var(--shadow-sm);
}

.config-btn.active {
    background: var(--gradient-primary);
    color: white;
    border-color: transparent;
    box-shadow: var(--shadow-md);
}

/* ==================== Test Box ==================== */
.test-box {
    background: var(--bg-elevated);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    padding: var(--spacing-2xl);
    box-shadow: var(--shadow-lg);
    position: relative;
    overflow: hidden;
}

.test-box::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--gradient-primary);
}

.test-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-xl);
    padding-bottom: var(--spacing-md);
    border-bottom: 1px solid var(--border-color);
}

.timer {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary);
}

.live-stats {
    display: flex;
    gap: var(--spacing-xl);
}

.live-stat {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.stat-label {
    font-size: 0.75rem;
    color: var(--text-tertiary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    font-weight: 600;
}

.stat-value {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-primary);
}

/* ==================== Text Display ==================== */
.text-display {
    font-family: var(--font-mono);
    font-size: 1.25rem;
    line-height: 2;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xl);
    padding: var(--spacing-xl);
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    min-height: 200px;
    user-select: none;
    letter-spacing: 0.02em;
}

.text-display .char {
    position: relative;
    transition: color var(--transition-fast);
}

.text-display .char.correct {
    color: var(--success);
}

.text-display .char.incorrect {
    color: var(--error);
    background: rgba(245, 101, 101, 0.1);
    border-radius: 2px;
}

.text-display .char.current {
    background: var(--primary);
    color: white;
    border-radius: 2px;
    animation: blink 1s infinite;
}

@keyframes blink {
    0%, 50% { opacity: 1; }
    51%, 100% { opacity: 0.3; }
}

/* ==================== Input Container ==================== */
.input-container {
    margin-bottom: var(--spacing-xl);
}

.typing-input {
    width: 100%;
    padding: var(--spacing-md) var(--spacing-lg);
    font-size: 1.125rem;
    font-family: var(--font-mono);
    background: var(--bg-secondary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-lg);
    color: var(--text-primary);
    transition: all var(--transition-fast);
}

.typing-input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

/* ==================== Buttons ==================== */
.test-controls {
    display: flex;
    justify-content: center;
    gap: var(--spacing-md);
}

.btn-primary,
.btn-secondary {
    padding: var(--spacing-md) var(--spacing-xl);
    border-radius: var(--radius-md);
    font-weight: 600;
    font-size: 1rem;
    cursor: pointer;
    transition: all var(--transition-fast);
    border: none;
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-family: var(--font-primary);
}

.btn-primary {
    background: var(--gradient-primary);
    color: white;
    box-shadow: var(--shadow-md);
}

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

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

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

.btn-secondary {
    background: var(--bg-secondary);
    color: var(--text-primary);
    border: 2px solid var(--border-color);
}

.btn-secondary:hover {
    background: var(--bg-tertiary);
    transform: translateY(-2px);
}

.btn-large {
    padding: var(--spacing-lg) var(--spacing-2xl);
    font-size: 1.125rem;
}

/* ==================== Practice Page ==================== */
.practice-options {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-xl);
}

.practice-card {
    background: var(--bg-elevated);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    padding: var(--spacing-xl);
    text-align: center;
    transition: all var(--transition-base);
    cursor: pointer;
    box-shadow: var(--shadow-md);
}

.practice-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-xl);
    border-color: var(--primary);
}

.practice-icon {
    font-size: 3rem;
    margin-bottom: var(--spacing-md);
}

.practice-card h3 {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
}

.practice-card p {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-lg);
}

/* ==================== Lessons Page ==================== */
.lessons-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-xl);
}

.lesson-card {
    background: var(--bg-elevated);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    padding: var(--spacing-xl);
    box-shadow: var(--shadow-md);
    transition: all var(--transition-base);
}

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

.lesson-number {
    width: 48px;
    height: 48px;
    background: var(--gradient-primary);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: var(--spacing-md);
}

.lesson-card h3 {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-sm);
}

.lesson-card p {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-lg);
}

.lesson-progress {
    margin-bottom: var(--spacing-lg);
}

.progress-bar {
    width: 100%;
    height: 8px;
    background: var(--bg-secondary);
    border-radius: 999px;
    overflow: hidden;
    margin-bottom: var(--spacing-sm);
}

.progress-fill {
    height: 100%;
    background: var(--gradient-primary);
    transition: width var(--transition-slow);
}

.lesson-progress span {
    font-size: 0.875rem;
    color: var(--text-tertiary);
}

/* ==================== Certificate Page ==================== */
.certificate-info {
    max-width: 700px;
    margin: 0 auto;
}

.info-card {
    background: var(--bg-elevated);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    padding: var(--spacing-2xl);
    box-shadow: var(--shadow-lg);
}

.info-card h3 {
    font-size: 1.5rem;
    margin-bottom: var(--spacing-md);
}

.info-card p {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-lg);
    line-height: 1.8;
}

.info-card ul {
    list-style: none;
    margin-bottom: var(--spacing-xl);
}

.info-card li {
    padding: var(--spacing-sm) 0;
    color: var(--text-secondary);
}

/* ==================== Modal ==================== */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 2000;
    align-items: center;
    justify-content: center;
}

.modal.active {
    display: flex;
}

.modal-backdrop {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.6);
    backdrop-filter: blur(4px);
    animation: fadeIn var(--transition-base);
}

.modal-content {
    position: relative;
    background: var(--bg-elevated);
    border-radius: var(--radius-2xl);
    max-width: 600px;
    width: 90%;
    max-height: 90vh;
    overflow-y: auto;
    box-shadow: var(--shadow-xl);
    animation: slideUp var(--transition-base);
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.modal-close {
    position: absolute;
    top: var(--spacing-md);
    right: var(--spacing-md);
    background: var(--bg-secondary);
    border: none;
    border-radius: var(--radius-md);
    width: 36px;
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    color: var(--text-primary);
    transition: all var(--transition-fast);
    z-index: 10;
}

.modal-close:hover {
    background: var(--bg-tertiary);
    transform: rotate(90deg);
}

.modal-header {
    text-align: center;
    padding: var(--spacing-2xl);
    border-bottom: 1px solid var(--border-color);
}

.success-icon {
    margin-bottom: var(--spacing-md);
}

.modal-header h2 {
    font-size: 2rem;
    margin-bottom: var(--spacing-sm);
}

.modal-header p {
    color: var(--text-secondary);
}

.modal-body {
    padding: var(--spacing-2xl);
}

.results-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--spacing-md);
}

.result-card {
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    text-align: center;
    transition: all var(--transition-fast);
}

.result-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.result-card.featured {
    grid-column: span 1;
    background: var(--gradient-primary);
    color: white;
}

.result-icon {
    font-size: 2rem;
    margin-bottom: var(--spacing-sm);
}

.result-label {
    font-size: 0.875rem;
    color: inherit;
    opacity: 0.8;
    margin-bottom: var(--spacing-sm);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    font-weight: 600;
}

.result-value {
    font-size: 2.5rem;
    font-weight: 700;
    color: inherit;
}

.result-desc {
    font-size: 0.75rem;
    opacity: 0.7;
    margin-top: var(--spacing-xs);
}

.modal-footer {
    padding: var(--spacing-xl) var(--spacing-2xl);
    border-top: 1px solid var(--border-color);
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
}

/* ==================== Certificate Modal ==================== */
.certificate-modal {
    max-width: 800px;
}

.certificate {
    padding: var(--spacing-2xl);
}

.certificate-border {
    border: 4px solid var(--primary);
    border-radius: var(--radius-xl);
    padding: var(--spacing-2xl);
    position: relative;
    background: linear-gradient(135deg, rgba(102, 126, 234, 0.05) 0%, rgba(118, 75, 162, 0.05) 100%);
}

.certificate-header {
    text-align: center;
    margin-bottom: var(--spacing-xl);
}

.certificate-header h2 {
    font-size: 2rem;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--spacing-sm);
}

.certificate-header p {
    color: var(--text-secondary);
    font-style: italic;
}

.certificate-name {
    font-size: 2.5rem;
    font-weight: 700;
    text-align: center;
    margin: var(--spacing-xl) 0;
    color: var(--text-primary);
    border-bottom: 2px solid var(--primary);
    padding-bottom: var(--spacing-md);
}

.certificate-body {
    text-align: center;
}

.certificate-body p {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-lg);
}

.certificate-stats {
    display: flex;
    justify-content: center;
    gap: var(--spacing-2xl);
    margin: var(--spacing-xl) 0;
}

.cert-stat {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.cert-label {
    font-size: 0.875rem;
    color: var(--text-tertiary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.cert-value {
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary);
}

.certificate-date {
    margin-top: var(--spacing-xl);
    color: var(--text-tertiary);
    font-style: italic;
}

.certificate-seal {
    position: absolute;
    bottom: var(--spacing-xl);
    right: var(--spacing-xl);
}

.name-input {
    flex: 1;
    padding: var(--spacing-md) var(--spacing-lg);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    background: var(--bg-secondary);
    color: var(--text-primary);
    font-family: var(--font-primary);
    font-size: 1rem;
}

.name-input:focus {
    outline: none;
    border-color: var(--primary);
}

/* ==================== Footer ==================== */
.footer {
    background: var(--bg-secondary);
    border-top: 1px solid var(--border-color);
    padding: var(--spacing-xl) 0;
    margin-top: var(--spacing-2xl);
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: var(--spacing-md);
}

.footer-content p {
    color: var(--text-secondary);
}

.footer-links {
    display: flex;
    gap: var(--spacing-lg);
}

.footer-links a {
    color: var(--text-secondary);
    text-decoration: none;
    transition: color var(--transition-fast);
}

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

/* ==================== Responsive Design ==================== */
@media (max-width: 768px) {
    .hero h1 {
        font-size: 2rem;
    }
    
    .config-panel {
        flex-direction: column;
        gap: var(--spacing-lg);
    }
    
    .nav-menu {
        display: none;
    }
    
    .test-header {
        flex-direction: column;
        gap: var(--spacing-md);
    }
    
    .results-grid {
        grid-template-columns: 1fr;
    }
    
    .result-card.featured {
        grid-column: span 1;
    }
    
    .certificate-stats {
        flex-direction: column;
        gap: var(--spacing-md);
    }
    
    .footer-content {
        flex-direction: column;
        text-align: center;
    }
}

/* ==================== Animations ==================== */
@keyframes pulse {
    0%, 100% {
        opacity: 1;
    }
    50% {
        opacity: 0.5;
    }
}

.loading {
    animation: pulse 2s cubic-bezier(0.4, 0, 0.6, 1) infinite;
}

/* ==================== Utility Classes ==================== */
.text-center {
    text-align: center;
}

.mt-1 { margin-top: var(--spacing-sm); }
.mt-2 { margin-top: var(--spacing-md); }
.mt-3 { margin-top: var(--spacing-lg); }
.mt-4 { margin-top: var(--spacing-xl); }

.mb-1 { margin-bottom: var(--spacing-sm); }
.mb-2 { margin-bottom: var(--spacing-md); }
.mb-3 { margin-bottom: var(--spacing-lg); }
.mb-4 { margin-bottom: var(--spacing-xl); }

.hidden {
    display: none !important;
}