/**
 * English Grammar Practice Styles
 * english.e-scholar.foundation
 * 
 * Color scheme from e-scholar.foundation:
 * Primary Blue: #1e3a8a
 * Primary Green: #16a34a
 * Gradient: linear-gradient(135deg, #1e3a8a 0%, #16a34a 100%)
 */

/* ==========================================
   CSS Variables & Theming
   ========================================== */
:root {
    /* Primary Colors */
    --primary-blue: #1e3a8a;
    --primary-green: #16a34a;
    --primary-gradient: linear-gradient(135deg, #1e3a8a 0%, #16a34a 100%);
    
    /* Light Theme (Default) */
    --bg-primary: #ffffff;
    --bg-secondary: #f8f9fa;
    --bg-tertiary: #e9ecef;
    --text-primary: #333333;
    --text-secondary: #666666;
    --text-muted: #999999;
    --border-color: #e9ecef;
    --card-bg: #ffffff;
    --card-shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
    
    /* Feedback Colors */
    --success-color: #16a34a;
    --success-bg: #f0fdf4;
    --success-border: #bbf7d0;
    --error-color: #ef4444;
    --error-bg: #fef2f2;
    --error-border: #fecaca;
    --warning-color: #f59e0b;
    --warning-bg: #fffbeb;
    
    /* Typography */
    --font-primary: 'Plus Jakarta Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-mono: 'JetBrains Mono', 'Courier New', monospace;
    
    /* Spacing */
    --spacing-xs: 4px;
    --spacing-sm: 8px;
    --spacing-md: 16px;
    --spacing-lg: 24px;
    --spacing-xl: 32px;
    --spacing-2xl: 48px;
    
    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    --radius-full: 50px;
    
    /* Transitions */
    --transition-fast: 0.15s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
}

/* Dark Theme */
[data-theme="dark"] {
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;
    --text-primary: #f1f5f9;
    --text-secondary: #cbd5e1;
    --text-muted: #94a3b8;
    --border-color: #334155;
    --card-bg: #1e293b;
    --card-shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
    --success-bg: #052e16;
    --success-border: #166534;
    --error-bg: #450a0a;
    --error-border: #991b1b;
}

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

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

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

.app-container {
    max-width: 900px;
    margin: 0 auto;
    padding: var(--spacing-md);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* ==========================================
   Header Styles
   ========================================== */
.header {
    position: relative;
    z-index: 100;
    background: var(--primary-gradient);
    color: white;
    padding: var(--spacing-lg) var(--spacing-xl);
    border-radius: var(--radius-xl) var(--radius-xl) 0 0;
    overflow: visible;
}

.header-background {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: 
        radial-gradient(circle at 20% 50%, rgba(255, 255, 255, 0.1) 0%, transparent 50%),
        radial-gradient(circle at 80% 80%, rgba(255, 255, 255, 0.08) 0%, transparent 50%);
    pointer-events: none;
}

.header-content {
    position: relative;
    z-index: 10;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: var(--spacing-md);
}

.logo-section {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    text-decoration: none;
    color: white;
}

.logo-icon {
    font-size: 2.5rem;
    animation: gentle-pulse 3s ease-in-out infinite;
}

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

.logo-text {
    display: flex;
    flex-direction: column;
}

.logo-main {
    font-size: 1.5rem;
    font-weight: 700;
    letter-spacing: -0.5px;
    line-height: 1.2;
}

.logo-sub {
    font-size: 0.875rem;
    font-weight: 400;
    opacity: 0.85;
}

.header-controls {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.toggle-btn {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-sm) var(--spacing-md);
    background: rgba(255, 255, 255, 0.15);
    border: 1px solid rgba(255, 255, 255, 0.25);
    border-radius: var(--radius-full);
    color: white;
    cursor: pointer;
    transition: var(--transition-normal);
    font-family: var(--font-primary);
    font-size: 0.875rem;
    font-weight: 500;
}

.toggle-btn:hover {
    background: rgba(255, 255, 255, 0.25);
    transform: translateY(-1px);
}

.toggle-icon {
    font-size: 1.125rem;
}

.toggle-label {
    font-weight: 600;
}

/* Language Dropdown */
.language-toggle {
    position: relative;
    z-index: 1000;
    cursor: pointer;
}

.language-toggle button {
    position: relative;
    z-index: 2;
    cursor: pointer !important;
}

.dropdown-menu {
    position: absolute;
    top: calc(100% + 8px);
    right: 0;
    background: var(--card-bg);
    border-radius: var(--radius-xl);
    box-shadow: 0 10px 40px rgba(0, 0, 0, 0.3);
    border: 1px solid var(--border-color);
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: var(--transition-normal);
    z-index: 1;
    min-width: 200px;
    width: max-content;
    overflow: hidden;
    pointer-events: none;
}

.dropdown-menu.show {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
    pointer-events: auto;
    z-index: 9999;
}

.dropdown-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-md);
    min-height: 48px;
    color: var(--text-primary);
    text-decoration: none;
    transition: var(--transition-fast);
    width: 100%;
    box-sizing: border-box;
    white-space: nowrap;
}

.dropdown-item:hover {
    background: var(--bg-secondary);
}

.dropdown-item.active {
    background: var(--success-bg);
    color: var(--success-color);
    font-weight: 600;
}

.header-tagline {
    position: relative;
    z-index: 1;
    text-align: center;
    font-size: 1rem;
    font-weight: 400;
    opacity: 0.9;
    margin-top: var(--spacing-md);
    padding-top: var(--spacing-md);
    border-top: 1px solid rgba(255, 255, 255, 0.2);
}

/* ==========================================
   Main Content
   ========================================== */
.main-content {
    flex: 1;
    background: var(--bg-primary);
    padding: var(--spacing-xl);
}

/* Welcome Section */
.welcome-section {
    text-align: center;
    margin-bottom: var(--spacing-2xl);
}

.welcome-title {
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--primary-blue);
    margin-bottom: var(--spacing-md);
}

[data-theme="dark"] .welcome-title {
    color: var(--text-primary);
}

.welcome-message {
    font-size: 1.0625rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
    line-height: 1.7;
}

/* Section Title */
.section-title {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: var(--spacing-lg);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.section-title::before {
    content: '';
    width: 4px;
    height: 24px;
    background: var(--primary-gradient);
    border-radius: 2px;
}

/* ==========================================
   Category Grid
   ========================================== */
.category-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: var(--spacing-md);
}

.category-card {
    background: var(--card-bg);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    cursor: pointer;
    transition: var(--transition-normal);
    text-decoration: none;
    color: inherit;
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.category-card:hover {
    border-color: var(--primary-blue);
    transform: translateY(-4px);
    box-shadow: var(--card-shadow);
}

.category-card:active {
    transform: translateY(-2px);
}

.category-header {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
}

.category-icon {
    font-size: 2rem;
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
}

.category-name {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--primary-blue);
}

[data-theme="dark"] .category-name {
    color: var(--text-primary);
}

.category-description {
    font-size: 0.9375rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

/* ==========================================
   Practice Page Styles
   ========================================== */
.practice-container {
    max-width: 700px;
    margin: 0 auto;
}

/* Breadcrumb */
.breadcrumb {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-lg);
    font-size: 0.9375rem;
}

.breadcrumb a {
    color: var(--primary-blue);
    text-decoration: none;
    transition: var(--transition-fast);
}

.breadcrumb a:hover {
    text-decoration: underline;
}

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

.breadcrumb-current {
    color: var(--text-secondary);
    font-weight: 500;
}

/* Test page: mode banner and question nav */
.test-mode-banner {
    background: linear-gradient(135deg, #fef3c7 0%, #fde68a 100%);
    border: 1px solid #f59e0b;
    color: #92400e;
    padding: var(--spacing-sm) var(--spacing-lg);
    margin-bottom: var(--spacing-md);
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}
[data-theme="dark"] .test-mode-banner {
    background: linear-gradient(135deg, rgba(245, 158, 11, 0.2) 0%, rgba(217, 119, 6, 0.2) 100%);
    border-color: #d97706;
    color: #fcd34d;
}
.test-mode-icon { font-size: 1.125rem; }
.test-question-nav {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-between;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
    padding: var(--spacing-md);
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
}
.test-position { font-weight: 600; color: var(--text-secondary); }
.test-nav-buttons { display: flex; gap: var(--spacing-sm); }
.btn-sm { padding: var(--spacing-xs) var(--spacing-md); font-size: 0.875rem; }
.btn.disabled, span.btn.disabled { opacity: 0.6; cursor: not-allowed; pointer-events: none; }

/* Question Card */
.question-card {
    background: var(--card-bg);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-lg);
    overflow: hidden;
    margin-bottom: var(--spacing-lg);
}

.question-header {
    background: var(--bg-secondary);
    padding: var(--spacing-md) var(--spacing-lg);
    border-bottom: 1px solid var(--border-color);
}

.question-meta {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-md);
    font-size: 0.875rem;
}

.question-meta-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
}

.meta-label {
    color: var(--text-muted);
    font-weight: 500;
}

.meta-value {
    color: var(--primary-blue);
    font-weight: 600;
}

[data-theme="dark"] .meta-value {
    color: var(--primary-green);
}

/* Tip Box */
.tip-box {
    background: linear-gradient(135deg, rgba(30, 58, 138, 0.08) 0%, rgba(22, 163, 74, 0.08) 100%);
    border-left: 4px solid var(--primary-blue);
    padding: var(--spacing-md) var(--spacing-lg);
    margin: var(--spacing-md) var(--spacing-lg);
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
}

.tip-label {
    font-size: 0.8125rem;
    font-weight: 700;
    color: var(--primary-blue);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: var(--spacing-xs);
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
}

[data-theme="dark"] .tip-label {
    color: var(--primary-green);
}

.tip-text {
    font-size: 0.9375rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

/* Question Body */
.question-body {
    padding: var(--spacing-lg);
}

.question-text {
    font-size: 1.25rem;
    font-weight: 500;
    color: var(--text-primary);
    margin-bottom: var(--spacing-lg);
    line-height: 1.5;
}

.question-blank {
    display: inline-block;
    min-width: 100px;
    border-bottom: 3px solid var(--primary-blue);
    margin: 0 4px;
}

/* Answer Options */
.answer-label {
    font-size: 0.9375rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-md);
    font-weight: 500;
}

.answer-options {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.answer-option {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    padding: var(--spacing-md) var(--spacing-lg);
    background: var(--bg-secondary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: var(--transition-normal);
}

.answer-option:hover {
    border-color: var(--primary-blue);
    background: var(--bg-primary);
}

.answer-option.selected {
    border-color: var(--primary-blue);
    background: rgba(30, 58, 138, 0.08);
}

.answer-option.correct {
    border-color: var(--success-color);
    background: var(--success-bg);
}

.answer-option.incorrect {
    border-color: var(--error-color);
    background: var(--error-bg);
}

.answer-option.disabled {
    pointer-events: none;
}

.answer-option input[type="radio"] {
    display: none;
}

.option-letter {
    width: 36px;
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-tertiary);
    border-radius: var(--radius-sm);
    font-weight: 700;
    font-size: 0.9375rem;
    color: var(--text-secondary);
    transition: var(--transition-fast);
}

.answer-option.selected .option-letter {
    background: var(--primary-blue);
    color: white;
}

.answer-option.correct .option-letter {
    background: var(--success-color);
    color: white;
}

.answer-option.incorrect .option-letter {
    background: var(--error-color);
    color: white;
}

.option-text {
    flex: 1;
    font-size: 1rem;
    color: var(--text-primary);
}

/* Feedback Box */
.feedback-box {
    margin-top: var(--spacing-lg);
    padding: var(--spacing-lg);
    border-radius: var(--radius-md);
    display: none;
}

.feedback-box.show {
    display: block;
    animation: slideIn 0.3s ease;
}

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

.feedback-box.correct {
    background: var(--success-bg);
    border: 2px solid var(--success-border);
}

.feedback-box.incorrect {
    background: var(--error-bg);
    border: 2px solid var(--error-border);
}

.feedback-header {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
}

.feedback-icon {
    font-size: 1.5rem;
}

.feedback-title {
    font-size: 1.25rem;
    font-weight: 700;
}

.feedback-box.correct .feedback-title {
    color: var(--success-color);
}

.feedback-box.incorrect .feedback-title {
    color: var(--error-color);
}

.feedback-explanation {
    font-size: 0.9375rem;
    color: var(--text-primary);
    line-height: 1.7;
}

.encouragement-message {
    margin-top: var(--spacing-md);
    padding-top: var(--spacing-md);
    border-top: 1px solid var(--border-color);
    font-weight: 600;
    font-size: 0.9375rem;
}

.feedback-box.correct .encouragement-message {
    color: var(--success-color);
}

.feedback-box.incorrect .encouragement-message {
    color: var(--text-secondary);
}

/* Action Buttons */
.action-buttons {
    display: flex;
    gap: var(--spacing-md);
    margin-top: var(--spacing-lg);
    flex-wrap: wrap;
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-md) var(--spacing-xl);
    font-family: var(--font-primary);
    font-size: 1rem;
    font-weight: 600;
    border-radius: var(--radius-full);
    cursor: pointer;
    transition: var(--transition-normal);
    text-decoration: none;
    border: 2px solid transparent;
}

.btn-primary {
    background: var(--primary-gradient);
    color: white;
    border: none;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(30, 58, 138, 0.3);
}

.btn-primary:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
    box-shadow: none;
}

.btn-secondary {
    background: var(--bg-primary);
    color: var(--primary-blue);
    border-color: var(--primary-blue);
}

.btn-secondary:hover {
    background: var(--primary-blue);
    color: white;
    transform: translateY(-2px);
}

.btn-icon {
    font-size: 1.125rem;
}

/* ==========================================
   Stats Bar
   ========================================== */
.stats-bar {
    background: var(--card-bg);
    border-top: 1px solid var(--border-color);
    padding: var(--spacing-md) var(--spacing-lg);
}

.stats-container {
    display: flex;
    align-items: center;
    justify-content: center;
    flex-wrap: wrap;
    gap: var(--spacing-lg);
}

.stat-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    font-size: 0.875rem;
}

.stat-icon {
    font-size: 1rem;
}

.stat-label {
    color: var(--text-secondary);
}

.stat-value {
    font-weight: 700;
    color: var(--primary-blue);
}

[data-theme="dark"] .stat-value {
    color: var(--primary-green);
}

.reset-btn {
    padding: var(--spacing-sm);
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: var(--transition-fast);
    font-size: 0.875rem;
}

.reset-btn:hover {
    background: var(--error-bg);
    border-color: var(--error-color);
}

/* ==========================================
   Footer
   ========================================== */
.footer {
    background: var(--bg-secondary);
    padding: var(--spacing-lg);
    border-radius: 0 0 var(--radius-xl) var(--radius-xl);
    text-align: center;
}

.footer-text {
    font-size: 0.9375rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xs);
}

.footer-copyright {
    font-size: 0.8125rem;
    color: var(--text-muted);
}

/* ==========================================
   Modal
   ========================================== */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    display: none;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    padding: var(--spacing-md);
}

.modal.show {
    display: flex;
}

.modal-content {
    background: var(--card-bg);
    padding: var(--spacing-xl);
    border-radius: var(--radius-lg);
    max-width: 400px;
    width: 100%;
    text-align: center;
}

.modal-content p {
    margin-bottom: var(--spacing-lg);
    font-size: 1rem;
    color: var(--text-primary);
}

.modal-actions {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
}

/* ==========================================
   Loading State
   ========================================== */
.loading {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-2xl);
    gap: var(--spacing-md);
}

.spinner {
    width: 48px;
    height: 48px;
    border: 4px solid var(--border-color);
    border-top-color: var(--primary-blue);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

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

.loading-text {
    color: var(--text-secondary);
    font-size: 0.9375rem;
}

/* ==========================================
   No Questions State
   ========================================== */
.no-questions {
    text-align: center;
    padding: var(--spacing-2xl);
    color: var(--text-secondary);
}

.no-questions-icon {
    font-size: 3rem;
    margin-bottom: var(--spacing-md);
}

.no-questions-text {
    font-size: 1.125rem;
    margin-bottom: var(--spacing-lg);
}

/* ==========================================
   Responsive Design
   ========================================== */
@media (max-width: 768px) {
    .app-container {
        padding: var(--spacing-sm);
    }
    
    .header {
        padding: var(--spacing-md);
        border-radius: var(--radius-lg) var(--radius-lg) 0 0;
    }
    
    .header-content {
        flex-direction: column;
        align-items: flex-start;
    }
    
    .logo-section {
        width: 100%;
    }
    
    .logo-main {
        font-size: 1.25rem;
    }
    
    .header-controls {
        width: 100%;
        justify-content: flex-end;
    }
    
    .header-tagline {
        font-size: 0.875rem;
    }
    
    .main-content {
        padding: var(--spacing-md);
    }
    
    .welcome-title {
        font-size: 1.5rem;
    }
    
    .welcome-message {
        font-size: 1rem;
    }
    
    .category-grid {
        grid-template-columns: 1fr;
    }
    
    .question-text {
        font-size: 1.125rem;
    }
    
    .action-buttons {
        flex-direction: column;
    }
    
    .btn {
        width: 100%;
    }
    
    .stats-container {
        gap: var(--spacing-md);
    }
    
    .stat-item {
        font-size: 0.8125rem;
    }
    
    .stat-label {
        display: none;
    }
    
    .footer {
        border-radius: 0 0 var(--radius-lg) var(--radius-lg);
    }
}

@media (max-width: 480px) {
    .toggle-label {
        display: none;
    }
    
    .question-meta {
        flex-direction: column;
        gap: var(--spacing-xs);
    }
    
    .tip-box {
        margin: var(--spacing-sm);
        padding: var(--spacing-sm) var(--spacing-md);
    }
    
    .question-body {
        padding: var(--spacing-md);
    }
    
    .answer-option {
        padding: var(--spacing-sm) var(--spacing-md);
    }
    
    .option-letter {
        width: 32px;
        height: 32px;
        font-size: 0.875rem;
    }
}

/* ==========================================
   Print Styles
   ========================================== */
@media print {
    body {
        background: white;
    }
    
    .header-controls,
    .stats-bar,
    .action-buttons,
    .reset-btn {
        display: none;
    }
}