/* ============================================================================
   NISH Preparation - Modern Minimalist Design
   ============================================================================ */

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

:root {
    /* Colors */
    --color-primary: #4F46E5;
    --color-primary-dark: #4338CA;
    --color-success: #10B981;
    --color-warning: #F59E0B;
    --color-error: #EF4444;
    --color-gray-50: #F9FAFB;
    --color-gray-100: #F3F4F6;
    --color-gray-200: #E5E7EB;
    --color-gray-300: #D1D5DB;
    --color-gray-400: #9CA3AF;
    --color-gray-500: #6B7280;
    --color-gray-600: #4B5563;
    --color-gray-700: #374151;
    --color-gray-800: #1F2937;
    --color-gray-900: #111827;
    
    /* Typography */
    --font-primary: 'Poppins', sans-serif;
    --font-heading: 'Libre Baskerville', serif;
    --font-mono: 'IBM Plex Mono', monospace;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 0.75rem;
    --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;
    
    /* 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);
}

body {
    font-family: var(--font-primary);
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    color: var(--color-gray-900);
    line-height: 1.6;
}

.container {
    max-width: 900px;
    margin: 0 auto;
    padding: var(--spacing-xl);
}

/* ============================================================================
   Screen Management
   ============================================================================ */

.screen {
    display: none;
    animation: fadeIn 0.3s ease-in-out;
}

.screen.active {
    display: block;
}

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

/* ============================================================================
   Loading Overlay
   ============================================================================ */

.loading-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.7);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 9999;
}

.loading-overlay.hidden {
    display: none;
}

.spinner {
    width: 60px;
    height: 60px;
    border: 4px solid rgba(255, 255, 255, 0.3);
    border-top-color: white;
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

.spinner-small {
    width: 30px;
    height: 30px;
    border: 3px solid var(--color-gray-200);
    border-top-color: var(--color-primary);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
    margin: 0 auto;
}

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

/* ============================================================================
   Buttons
   ============================================================================ */

.btn {
    padding: var(--spacing-sm) var(--spacing-lg);
    font-family: var(--font-primary);
    font-size: 1rem;
    font-weight: 600;
    border: none;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all 0.2s ease;
    display: inline-block;
    text-align: center;
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.btn-primary {
    background-color: var(--color-primary);
    color: white;
}

.btn-primary:hover:not(:disabled) {
    background-color: var(--color-primary-dark);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.btn-secondary {
    background-color: var(--color-gray-200);
    color: var(--color-gray-700);
}

.btn-secondary:hover:not(:disabled) {
    background-color: var(--color-gray-300);
}

.btn-outline {
    background-color: white;
    color: var(--color-primary);
    border: 2px solid var(--color-primary);
}

.btn-outline:hover:not(:disabled) {
    background-color: var(--color-primary);
    color: white;
}

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

/* ============================================================================
   Login/Registration Screen
   ============================================================================ */

.auth-card {
    background: white;
    border-radius: var(--radius-xl);
    padding: var(--spacing-2xl);
    box-shadow: var(--shadow-xl);
    max-width: 450px;
    margin: 3rem auto;
}

.logo {
    font-family: var(--font-heading);
    font-size: 2rem;
    text-align: center;
    color: var(--color-primary);
    margin-bottom: var(--spacing-xl);
}

.auth-form h2 {
    font-size: 1.5rem;
    margin-bottom: var(--spacing-lg);
    color: var(--color-gray-800);
}

.form-group {
    margin-bottom: var(--spacing-lg);
}

.form-group label {
    display: block;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--color-gray-700);
    margin-bottom: var(--spacing-xs);
}

.form-group input {
    width: 100%;
    padding: var(--spacing-sm) var(--spacing-md);
    font-family: var(--font-primary);
    font-size: 1rem;
    border: 1px solid var(--color-gray-300);
    border-radius: var(--radius-md);
    transition: border-color 0.2s;
}

.form-group input:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.auth-form .btn {
    width: 100%;
    margin-top: var(--spacing-md);
}

.switch-auth {
    text-align: center;
    margin-top: var(--spacing-lg);
    font-size: 0.875rem;
    color: var(--color-gray-600);
}

.switch-auth a {
    color: var(--color-primary);
    text-decoration: none;
    font-weight: 600;
}

.switch-auth a:hover {
    text-decoration: underline;
}

.error-message {
    color: var(--color-error);
    font-size: 0.875rem;
    margin-top: var(--spacing-md);
    text-align: center;
}

.hidden {
    display: none !important;
}

/* ============================================================================
   Welcome Screen
   ============================================================================ */

.welcome-container {
    max-width: 1000px;
}

.welcome-header {
    text-align: center;
    background: white;
    border-radius: var(--radius-xl);
    padding: var(--spacing-xl);
    box-shadow: var(--shadow-md);
    margin-bottom: var(--spacing-xl);
}

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

.welcome-header h1 {
    font-family: var(--font-heading);
    font-size: 1.75rem;
    color: var(--color-gray-800);
    margin-bottom: var(--spacing-xs);
}

.welcome-subtitle {
    font-size: 1rem;
    color: var(--color-gray-600);
}

/* Stats Summary */
.stats-summary {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-xl);
}

.stat-box {
    background: white;
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    text-align: center;
    box-shadow: var(--shadow-sm);
}

.stat-box .stat-value {
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--color-primary);
}

.stat-box .stat-label {
    font-size: 0.875rem;
    color: var(--color-gray-600);
    margin-top: var(--spacing-xs);
}

/* Recommended Section */
.recommended-section {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    border-radius: var(--radius-xl);
    padding: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
    color: white;
}

.recommended-section h3 {
    font-size: 1.125rem;
    margin-bottom: var(--spacing-md);
}

.recommended-card {
    background: rgba(255, 255, 255, 0.15);
    border-radius: var(--radius-lg);
    padding: var(--spacing-md);
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--spacing-md);
}

.recommended-info {
    flex: 1;
}

.recommended-name {
    font-weight: 600;
    font-size: 1.125rem;
}

.recommended-reason {
    font-size: 0.875rem;
    opacity: 0.9;
    margin-top: var(--spacing-xs);
}

.recommended-card .btn {
    background: white;
    color: var(--color-primary);
    flex-shrink: 0;
}

.recommended-card .btn:hover {
    background: var(--color-gray-100);
}

/* Topics Section */
.topics-section {
    background: white;
    border-radius: var(--radius-xl);
    padding: var(--spacing-lg);
    box-shadow: var(--shadow-md);
    margin-bottom: var(--spacing-xl);
}

.topics-section h3 {
    font-size: 1.25rem;
    color: var(--color-gray-800);
    margin-bottom: var(--spacing-lg);
}

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

.loading-topics {
    text-align: center;
    padding: var(--spacing-xl);
    color: var(--color-gray-500);
}

.topic-group {
    border: 1px solid var(--color-gray-200);
    border-radius: var(--radius-lg);
    overflow: hidden;
}

.topic-header {
    background: var(--color-gray-50);
    padding: var(--spacing-md);
    display: flex;
    align-items: center;
    justify-content: space-between;
    cursor: pointer;
    user-select: none;
}

.topic-header:hover {
    background: var(--color-gray-100);
}

.topic-title {
    font-weight: 600;
    color: var(--color-gray-800);
}

.topic-accuracy {
    font-size: 0.875rem;
    color: var(--color-gray-600);
}

.topic-accuracy.high {
    color: var(--color-success);
}

.topic-accuracy.medium {
    color: var(--color-warning);
}

.topic-accuracy.low {
    color: var(--color-error);
}

.subtopics-list {
    display: none;
    padding: var(--spacing-sm);
    background: white;
}

.topic-group.expanded .subtopics-list {
    display: block;
}

.subtopic-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: background 0.2s;
    border: 1px solid var(--color-gray-200);
    background: white;
}

.subtopic-item:hover {
    background: var(--color-gray-50);
}

.subtopic-item.recommended {
    background: rgba(79, 70, 229, 0.1);
    border: 1px solid var(--color-primary);
}

.subtopic-item.has-session {
    border-color: var(--color-primary);
}

.subtopic-info {
    flex: 1;
}

.subtopic-name {
    font-weight: 500;
    color: var(--color-gray-800);
    font-size: 0.9375rem;
}

.subtopic-desc {
    font-size: 0.8125rem;
    color: var(--color-gray-500);
    margin-top: 2px;
}

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

.subtopic-buttons {
    display: flex;
    gap: var(--spacing-xs);
    align-items: center;
}

.learn-btn {
    padding: var(--spacing-xs) var(--spacing-md);
    font-size: 0.8125rem;
    background: var(--color-primary);
    color: white;
    border: none;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: background 0.2s;
    white-space: nowrap;
}

.learn-btn:hover {
    background: var(--color-primary-dark);
}

.subtopic-accuracy {
    font-size: 0.875rem;
    font-weight: 500;
    min-width: 45px;
    text-align: right;
}

.subtopic-accuracy.not-practiced {
    color: var(--color-gray-400);
}

.subtopic-accuracy.high {
    color: var(--color-success);
}

.subtopic-accuracy.medium {
    color: var(--color-warning);
}

.subtopic-accuracy.low {
    color: var(--color-error);
}

.practice-btn {
    padding: var(--spacing-xs) var(--spacing-md);
    font-size: 0.8125rem;
    background: var(--color-primary);
    color: white;
    border: none;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: background 0.2s;
}

.practice-btn:hover {
    background: var(--color-primary-dark);
}

/* Subtopic Item Container with Action Buttons */
.subtopic-item-container {
    margin-bottom: var(--spacing-sm);
}

.subtopic-actions {
    background: linear-gradient(135deg, #f0f4ff 0%, #e8f0fe 100%);
    border: 1px solid var(--color-primary);
    border-bottom: none;
    border-radius: var(--radius-md) var(--radius-md) 0 0;
    padding: var(--spacing-sm) var(--spacing-md);
}

.subtopic-actions-compact {
    background: var(--color-gray-50);
    border: 1px solid var(--color-gray-200);
    border-bottom: none;
}

.session-info {
    margin-bottom: var(--spacing-sm);
}

.session-progress-badge {
    display: inline-block;
    font-size: 0.8125rem;
    font-weight: 500;
    color: var(--color-primary);
    background: rgba(79, 70, 229, 0.1);
    padding: 0.25rem 0.5rem;
    border-radius: var(--radius-sm);
}

.action-buttons {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-xs);
}

.action-btn {
    padding: 0.375rem 0.75rem;
    font-size: 0.75rem;
    font-weight: 500;
    font-family: var(--font-primary);
    border: none;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all 0.2s ease;
    white-space: nowrap;
}

.action-btn-continue {
    background: var(--color-success);
    color: white;
}

.action-btn-continue:hover {
    background: #059669;
    transform: translateY(-1px);
    box-shadow: var(--shadow-sm);
}

.action-btn-delete {
    background: var(--color-error);
    color: white;
}

.action-btn-delete:hover {
    background: #dc2626;
    transform: translateY(-1px);
    box-shadow: var(--shadow-sm);
}

.action-btn-restart {
    background: var(--color-warning);
    color: white;
}

.action-btn-restart:hover {
    background: #d97706;
    transform: translateY(-1px);
    box-shadow: var(--shadow-sm);
}

.action-btn-learn {
    background: var(--color-gray-600);
    color: white;
}

.action-btn-learn:hover {
    background: var(--color-gray-700);
    transform: translateY(-1px);
    box-shadow: var(--shadow-sm);
}

/* Subtopic item adjustments when has session */
.subtopic-item-container .subtopic-item {
    border-radius: 0 0 var(--radius-md) var(--radius-md);
}

.subtopic-item.has-session {
    border-top: none;
    border-top-left-radius: 0;
    border-top-right-radius: 0;
    background: #fefefe;
}

/* Mobile responsiveness for action buttons */
@media (max-width: 640px) {
    .action-buttons {
        flex-direction: column;
    }
    
    .action-btn {
        width: 100%;
        text-align: center;
    }
}

/* Rules Section (collapsed) */
.rules-section {
    background: white;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
    margin-bottom: var(--spacing-xl);
}

.rules-section summary {
    padding: var(--spacing-md);
    cursor: pointer;
    font-weight: 500;
    color: var(--color-gray-700);
}

.rules-section[open] summary {
    border-bottom: 1px solid var(--color-gray-200);
}

.rules-list {
    list-style: none;
    padding: var(--spacing-md);
}

.rule-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-sm);
    font-size: 0.9375rem;
    color: var(--color-gray-700);
}

.rule-item:last-child {
    margin-bottom: 0;
}

.rule-icon {
    font-size: 1.25rem;
}

/* Mobile responsiveness */
@media (max-width: 640px) {
    .stats-summary {
        grid-template-columns: 1fr;
    }
    
    .recommended-card {
        flex-direction: column;
        text-align: center;
    }
    
    .subtopic-item {
        flex-direction: column;
        align-items: flex-start;
        gap: var(--spacing-sm);
    }
    
    .subtopic-stats {
        width: 100%;
        justify-content: space-between;
        flex-wrap: wrap;
    }
    
    .subtopic-buttons {
        flex-wrap: wrap;
        width: 100%;
    }
    
    .subtopic-buttons .practice-btn,
    .subtopic-buttons .learn-btn {
        flex: 1;
        min-width: 100px;
    }
}

/* ============================================================================
   Game Screen - Header with Back Button
   ============================================================================ */

.game-header {
    margin-bottom: var(--spacing-md);
}

.btn-back {
    background: transparent;
    color: white;
    border: 1px solid rgba(255, 255, 255, 0.5);
    padding: var(--spacing-xs) var(--spacing-md);
    font-size: 0.875rem;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all 0.2s;
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
}

.btn-back:hover {
    background: rgba(255, 255, 255, 0.15);
    border-color: rgba(255, 255, 255, 0.8);
}

/* ============================================================================
   Game Screen - Progress Section
   ============================================================================ */

.progress-section {
    background: white;
    border-radius: var(--radius-xl);
    padding: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
    box-shadow: var(--shadow-md);
}

.progress-circles {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-sm);
    justify-content: center;
}

.circle {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.875rem;
    font-weight: 600;
    transition: all 0.3s ease;
    cursor: pointer;
}

.circle.pending {
    background-color: var(--color-gray-200);
    color: var(--color-gray-600);
}

.circle.pending.generated {
    background-color: var(--color-gray-400);
    color: white;
}

.circle.correct {
    background-color: var(--color-success);
    color: white;
}

.circle.retry_once {
    background-color: var(--color-warning);
    color: white;
}

.circle.retry_three {
    background-color: var(--color-error);
    color: white;
}

.circle.active {
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.3);
    transform: scale(1.1);
}

/* ============================================================================
   Game Screen - Task Card
   ============================================================================ */

.task-card {
    background: white;
    border-radius: var(--radius-xl);
    padding: var(--spacing-2xl);
    box-shadow: var(--shadow-xl);
}

.task-header h2 {
    font-size: 1.5rem;
    color: var(--color-gray-800);
    margin-bottom: var(--spacing-lg);
}

.subtopic-label {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--color-primary);
    display: block;
    margin-bottom: var(--spacing-xs);
}

.task-question {
    margin-bottom: var(--spacing-xl);
}

.task-question p {
    font-size: 1.125rem;
    color: var(--color-gray-800);
    line-height: 1.8;
}

/* Task Media (images for geometry tasks) */
.task-media {
    margin-bottom: var(--spacing-xl);
    text-align: center;
}

.task-media .task-image {
    max-width: 100%;
    max-height: 300px;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--color-gray-200);
}

.task-options {
    display: grid;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-xl);
}

.option-btn {
    padding: var(--spacing-md);
    font-family: var(--font-primary);
    font-size: 1rem;
    text-align: left;
    background: var(--color-gray-50);
    border: 2px solid var(--color-gray-200);
    border-radius: var(--radius-lg);
    cursor: pointer;
    transition: all 0.2s;
}

.option-btn:hover {
    background: var(--color-gray-100);
    border-color: var(--color-gray-300);
}

.option-btn.selected {
    background: var(--color-primary);
    color: white;
    border-color: var(--color-primary);
}

.option-btn.correct {
    background: var(--color-success) !important;
    color: white !important;
    border-color: var(--color-success) !important;
    pointer-events: none;
}

.option-btn.correct:hover {
    background: var(--color-success) !important;
    color: white !important;
    border-color: var(--color-success) !important;
}

.option-btn.incorrect {
    background: var(--color-error) !important;
    color: white !important;
    border-color: var(--color-error) !important;
    pointer-events: none;
}

.option-btn.incorrect:hover {
    background: var(--color-error) !important;
    color: white !important;
    border-color: var(--color-error) !important;
}

/* DEBUG MODE: Show correct answer before submission in grey */
.option-btn.debug-correct {
    background: var(--color-gray-300);
    border-color: var(--color-gray-500);
    border-width: 2px;
}

.option-btn.debug-correct:hover {
    background: var(--color-gray-400);
    border-color: var(--color-gray-600);
}

/* Selected state should override debug-correct but not correct/incorrect */
.option-btn.selected {
    background: var(--color-primary);
    color: white;
    border-color: var(--color-primary);
}

.task-feedback {
    display: flex;
    align-items: flex-start;
    gap: var(--spacing-md);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    margin-bottom: var(--spacing-xl);
    animation: slideDown 0.3s ease;
}

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

.task-feedback-success {
    background-color: #ECFDF5;
    border: 2px solid var(--color-success);
}

.task-feedback-warning {
    background-color: #FFFBEB;
    border: 2px solid var(--color-warning);
}

.task-feedback-error {
    background-color: #FEF2F2;
    border: 2px solid var(--color-error);
}

.task-feedback-info {
    background-color: #EFF6FF;
    border: 2px solid #3B82F6;
}

.task-feedback .feedback-icon {
    font-size: 2rem;
    flex-shrink: 0;
}

.task-feedback .feedback-content {
    flex: 1;
}

.task-feedback .feedback-content h3 {
    font-size: 1.125rem;
    color: var(--color-gray-800);
    margin-bottom: var(--spacing-xs);
}

.task-feedback .feedback-content p {
    font-size: 1rem;
    color: var(--color-gray-700);
    margin: 0;
}

.task-solution {
    background: var(--color-gray-50);
    border-left: 4px solid var(--color-primary);
    padding: var(--spacing-lg);
    border-radius: var(--radius-md);
    margin-bottom: var(--spacing-xl);
}

.correct-answer-display {
    background: var(--color-success);
    color: white;
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    margin-bottom: var(--spacing-lg);
    font-size: 1.1rem;
    text-align: center;
    box-shadow: var(--shadow-md);
}

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

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

.solution-header h3 {
    font-size: 1.125rem;
    color: var(--color-gray-800);
}

#solution-text {
    color: var(--color-gray-700);
    line-height: 1.8;
}

/* Solution Steps - Step-by-step solution display */
.solution-steps {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.solution-step {
    background: white;
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
    border: 1px solid var(--color-gray-200);
    transition: box-shadow 0.2s ease;
}

.solution-step:hover {
    box-shadow: var(--shadow-md);
}

.step-header {
    display: flex;
    align-items: flex-start;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-sm);
}

.step-number {
    background: var(--color-primary);
    color: white;
    font-size: 0.75rem;
    font-weight: 600;
    padding: 0.25rem 0.5rem;
    border-radius: var(--radius-sm);
    white-space: nowrap;
    flex-shrink: 0;
}

.step-description {
    font-weight: 500;
    color: var(--color-gray-800);
    line-height: 1.5;
}

.step-calculation {
    background: var(--color-gray-100);
    border-radius: var(--radius-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    font-family: var(--font-mono);
    font-size: 0.9rem;
    color: var(--color-gray-700);
    white-space: pre-wrap;
    line-height: 1.6;
    overflow-x: auto;
}

.solution-formulas {
    margin-top: var(--spacing-lg);
    padding-top: var(--spacing-lg);
    border-top: 1px solid var(--color-gray-200);
}

.solution-formulas h4 {
    font-size: 1rem;
    color: var(--color-gray-800);
    margin-bottom: var(--spacing-sm);
}

.solution-formulas ul {
    list-style: none;
    padding: 0;
}

.solution-formulas li {
    background: linear-gradient(135deg, #f0f9ff 0%, #e0f2fe 100%);
    border-left: 3px solid var(--color-primary);
    padding: var(--spacing-sm) var(--spacing-md);
    margin-bottom: var(--spacing-xs);
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
    font-family: var(--font-mono);
    font-size: 0.85rem;
    color: var(--color-gray-700);
}

.task-actions {
    display: flex;
    gap: var(--spacing-md);
    flex-wrap: wrap;
}

.task-actions .btn {
    flex: 1;
    min-width: 150px;
}

/* ============================================================================
   Completion Screen
   ============================================================================ */

.completion-card {
    background: white;
    border-radius: var(--radius-xl);
    padding: var(--spacing-2xl);
    box-shadow: var(--shadow-xl);
    text-align: center;
    margin-top: 3rem;
}

.completion-icon {
    font-size: 4rem;
    margin-bottom: var(--spacing-lg);
}

.completion-card h1 {
    font-family: var(--font-heading);
    font-size: 2rem;
    color: var(--color-gray-800);
    margin-bottom: var(--spacing-sm);
}

.completion-subtitle {
    font-size: 1.125rem;
    color: var(--color-gray-600);
    margin-bottom: var(--spacing-2xl);
}

.stats-section {
    margin-bottom: var(--spacing-2xl);
}

.stats-section h3 {
    font-size: 1.25rem;
    color: var(--color-gray-800);
    margin-bottom: var(--spacing-lg);
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: var(--spacing-lg);
}

.stat-item {
    padding: var(--spacing-lg);
    background: var(--color-gray-50);
    border-radius: var(--radius-lg);
}

.stat-value {
    font-size: 2rem;
    font-weight: 700;
    color: var(--color-gray-800);
    margin-bottom: var(--spacing-xs);
}

.stat-label {
    font-size: 0.875rem;
    color: var(--color-gray-600);
}

.stat-success .stat-value {
    color: var(--color-success);
}

.stat-warning .stat-value {
    color: var(--color-warning);
}

.stat-error .stat-value {
    color: var(--color-error);
}

/* ============================================================================
   Modals
   ============================================================================ */

.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.6);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    animation: fadeIn 0.2s ease;
}

.modal-content {
    background: white;
    border-radius: var(--radius-xl);
    padding: var(--spacing-2xl);
    box-shadow: var(--shadow-xl);
    text-align: center;
    max-width: 500px;
    width: 90%;
    position: relative;
    animation: slideUp 0.3s ease;
}

.modal-large {
    max-width: 700px;
}

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

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

.modal-content h2 {
    font-size: 1.5rem;
    color: var(--color-gray-800);
    margin-bottom: var(--spacing-md);
}

.modal-content p {
    color: var(--color-gray-600);
    margin-bottom: var(--spacing-lg);
}

.modal-close {
    position: absolute;
    top: var(--spacing-lg);
    right: var(--spacing-lg);
    width: 32px;
    height: 32px;
    border: none;
    background: var(--color-gray-100);
    border-radius: 50%;
    font-size: 1.5rem;
    line-height: 1;
    cursor: pointer;
    transition: background 0.2s;
}

.modal-close:hover {
    background: var(--color-gray-200);
}

.generating-spinner {
    margin: var(--spacing-lg) 0;
}

.generating-spinner p {
    margin-top: var(--spacing-md);
    color: var(--color-gray-600);
}

.explanation-content {
    text-align: left;
    max-height: 500px;
    overflow-y: auto;
}

.explanation-loading {
    text-align: center;
    padding: var(--spacing-2xl);
}

.explanation-text {
    color: var(--color-gray-700);
    line-height: 1.8;
}

.explanation-text h3 {
    font-size: 1.25rem;
    color: var(--color-gray-900);
    margin-bottom: var(--spacing-md);
    font-weight: 600;
}

.explanation-text h4 {
    font-size: 1rem;
    color: var(--color-gray-800);
    margin-top: var(--spacing-lg);
    margin-bottom: var(--spacing-sm);
    font-weight: 600;
}

.explanation-text .explanation-main {
    margin-bottom: var(--spacing-lg);
    white-space: pre-wrap;
}

.explanation-text ul {
    padding-left: var(--spacing-lg);
    margin-bottom: var(--spacing-md);
}

.explanation-text li {
    margin-bottom: var(--spacing-xs);
}

/* ============================================================================
   Fraction Display - Vertical Format
   ============================================================================ */

.fraction {
    display: inline-flex;
    flex-direction: column;
    align-items: center;
    vertical-align: middle;
    text-align: center;
    font-size: 0.9em;
    margin: 0 0.15em;
}

.fraction .numerator {
    border-bottom: 1px solid currentColor;
    padding: 0 0.3em 0.1em;
    line-height: 1;
}

.fraction .denominator {
    padding: 0.1em 0.3em 0;
    line-height: 1;
}

/* Mixed numbers (e.g., 1 1/2) */
.mixed-number {
    display: inline-flex;
    align-items: center;
    gap: 0.2em;
    vertical-align: middle;
}

.mixed-number .whole {
    font-weight: 500;
}

/* Ensure fractions work well in different contexts */
.step-calculation .fraction,
.solution-formulas .fraction,
.explanation-text .fraction,
.task-question .fraction {
    font-size: 1em;
}

/* Larger fractions for headings */
h3 .fraction,
h4 .fraction {
    font-size: 0.85em;
}

/* ============================================================================
   Responsive Design
   ============================================================================ */

@media (max-width: 768px) {
    .container {
        padding: var(--spacing-md);
    }
    
    .auth-card,
    .welcome-card,
    .task-card,
    .completion-card {
        padding: var(--spacing-lg);
    }
    
    .circle {
        width: 35px;
        height: 35px;
        font-size: 0.75rem;
    }
    
    .task-actions {
        flex-direction: column;
    }
    
    .task-actions .btn {
        width: 100%;
        min-width: 0;
    }
    
    .stats-grid {
        grid-template-columns: 1fr;
    }
}