/* ==========================================================================
   Vokabel - Vocabulary Trainer Design System
   A modern, Quizlet-inspired CSS design system for students aged 11-18.
   ========================================================================== */

/* --------------------------------------------------------------------------
   Google Font Import
   -------------------------------------------------------------------------- */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap');

/* --------------------------------------------------------------------------
   CSS Custom Properties (Design Tokens)
   -------------------------------------------------------------------------- */
:root {
    /* Primary Green */
    --color-primary: #2e7d32;
    --color-primary-light: #e8f5e9;
    --color-primary-dark: #1b5e20;

    /* Accent Colors */
    --color-blue: #1565c0;
    --color-purple: #7b1fa2;
    --color-orange: #e65100;
    --color-gold: #f9a825;

    /* Neutral Grays */
    --color-gray-50: #fafafa;
    --color-gray-100: #f5f5f5;
    --color-gray-200: #e8e8e8;
    --color-gray-300: #e0e0e0;
    --color-gray-400: #bdbdbd;
    --color-gray-500: #9e9e9e;
    --color-gray-600: #757575;
    --color-gray-700: #555555;
    --color-gray-800: #333333;
    --color-gray-900: #1a1a2e;

    /* Semantic Colors */
    --color-success: #2e7d32;
    --color-error: #c62828;
    --color-error-light: #ffebee;
    --color-error-border: #ef9a9a;
    --color-warning: #f9a825;

    /* Typography */
    --font-family: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.8rem;
    --font-size-base: 1rem;
    --font-size-md: 0.9rem;
    --font-size-lg: 1.1rem;
    --font-size-xl: 1.3rem;
    --font-size-2xl: 1.4rem;
    --font-size-3xl: 1.6rem;
    --font-size-4xl: 1.8rem;
    --line-height-base: 1.6;

    /* Shadows */
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.08);
    --shadow-md: 0 2px 8px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 4px 16px rgba(0, 0, 0, 0.12);
    --shadow-xl: 0 8px 30px rgba(0, 0, 0, 0.15);

    /* Border Radii */
    --radius-sm: 6px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-xl: 16px;
    --radius-pill: 999px;

    /* Spacing */
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    --space-2xl: 3rem;

    /* Transitions */
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s ease;
}

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

/* --------------------------------------------------------------------------
   Typography & Body
   -------------------------------------------------------------------------- */
body {
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    line-height: var(--line-height-base);
    color: var(--color-gray-900);
    background-color: var(--color-gray-100);
    padding-top: 76px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

h1, h2, h3, h4, h5, h6 {
    line-height: 1.3;
    font-weight: 700;
}

a {
    color: var(--color-primary);
    text-decoration: none;
}

a:hover {
    color: var(--color-primary-dark);
}

/* --------------------------------------------------------------------------
   Container
   -------------------------------------------------------------------------- */
.container {
    max-width: 900px;
    margin: 0 auto;
    padding: 0 1rem;
}

/* --------------------------------------------------------------------------
   Utility Classes
   -------------------------------------------------------------------------- */
.hidden {
    display: none;
}

/* --------------------------------------------------------------------------
   Card Component
   -------------------------------------------------------------------------- */
.card {
    background: #ffffff;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    padding: var(--space-lg);
    animation: fadeInUp 0.4s ease;
}

/* --------------------------------------------------------------------------
   Button Components
   -------------------------------------------------------------------------- */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.4rem;
    padding: 0.6rem 1.5rem;
    border-radius: var(--radius-md);
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    font-weight: 600;
    cursor: pointer;
    border: 2px solid transparent;
    transition: all var(--transition-fast);
    text-decoration: none;
    line-height: 1.4;
}

.btn:active {
    transform: scale(0.97);
}

.btn-primary {
    background-color: var(--color-primary);
    color: #ffffff;
    border-color: var(--color-primary);
}

.btn-primary:hover {
    background-color: var(--color-primary-dark);
    border-color: var(--color-primary-dark);
    color: #ffffff;
}

.btn-outline {
    background-color: transparent;
    color: var(--color-primary);
    border-color: var(--color-primary);
}

.btn-outline:hover {
    background-color: var(--color-primary-light);
    color: var(--color-primary);
}

.btn-danger {
    background-color: transparent;
    color: var(--color-error);
    border-color: var(--color-error);
}

.btn-danger:hover {
    background-color: var(--color-error-light);
    color: var(--color-error);
}

/* --------------------------------------------------------------------------
   Badge Components
   -------------------------------------------------------------------------- */
.badge {
    display: inline-flex;
    align-items: center;
    gap: 0.25rem;
    padding: 0.2rem 0.6rem;
    border-radius: var(--radius-pill);
    font-size: var(--font-size-xs);
    font-weight: 600;
    line-height: 1.4;
}

.badge-primary {
    background-color: var(--color-primary-light);
    color: var(--color-primary);
}

.badge-gold {
    background-color: #fff8e1;
    color: var(--color-gold);
}

/* --------------------------------------------------------------------------
   Progress Bar
   -------------------------------------------------------------------------- */
.progress-bar {
    width: 100%;
    height: 8px;
    background-color: var(--color-gray-200);
    border-radius: var(--radius-pill);
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background-color: var(--color-primary);
    border-radius: var(--radius-pill);
    transition: width 0.5s ease;
}

/* --------------------------------------------------------------------------
   Form Components
   -------------------------------------------------------------------------- */
.form-group {
    margin-bottom: var(--space-md);
}

.form-group label {
    display: block;
    font-weight: 500;
    margin-bottom: 0.3rem;
    font-size: var(--font-size-md);
    color: var(--color-gray-800);
}

.form-group input,
.form-group select {
    width: 100%;
    padding: 0.65rem 0.8rem;
    border: 1px solid #dddddd;
    border-radius: var(--radius-md);
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    color: var(--color-gray-900);
    background: #ffffff;
    transition: border-color var(--transition-fast);
    outline: none;
}

.form-group input:focus,
.form-group select:focus {
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(46, 125, 50, 0.12);
}

.form-row {
    display: flex;
    gap: 0.8rem;
    align-items: flex-end;
}

/* --------------------------------------------------------------------------
   Navigation Bar
   -------------------------------------------------------------------------- */
.nav-bar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background-color: #ffffff;
    box-shadow: var(--shadow-sm);
    height: 60px;
    display: flex;
    align-items: center;
    padding: 0 1.5rem;
}

.nav-bar .container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    width: 100%;
    max-width: 900px;
    margin: 0 auto;
}

.nav-logo {
    font-weight: 700;
    font-size: var(--font-size-xl);
    color: var(--color-primary);
    text-decoration: none;
}

.nav-logo:hover {
    color: var(--color-primary-dark);
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 1.5rem;
}

.nav-links a {
    text-decoration: none;
    color: var(--color-gray-700);
    font-weight: 500;
    font-size: var(--font-size-md);
    transition: color var(--transition-fast);
}

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

.nav-links a.active {
    color: var(--color-primary);
    font-weight: 600;
}

.nav-user {
    display: flex;
    align-items: center;
    gap: 0.8rem;
}

.nav-xp-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.3rem;
    padding: 0.25rem 0.7rem;
    border-radius: var(--radius-pill);
    background-color: var(--color-primary);
    color: #ffffff;
    font-size: var(--font-size-sm);
    font-weight: 600;
}

.nav-user-name {
    font-weight: 500;
    font-size: var(--font-size-md);
    color: var(--color-gray-800);
}

.btn-logout {
    background: none;
    border: 1px solid var(--color-gray-300);
    border-radius: var(--radius-md);
    padding: 0.3rem 0.8rem;
    font-family: var(--font-family);
    font-size: var(--font-size-sm);
    color: var(--color-gray-600);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.btn-logout:hover {
    border-color: var(--color-error);
    color: var(--color-error);
    background-color: var(--color-error-light);
}

/* --------------------------------------------------------------------------
   Keyframe Animations
   -------------------------------------------------------------------------- */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes shakeX {
    0%, 100% {
        transform: translateX(0);
    }
    20%, 60% {
        transform: translateX(-8px);
    }
    40%, 80% {
        transform: translateX(8px);
    }
}

@keyframes popIn {
    0% {
        transform: scale(0.5);
        opacity: 0;
    }
    60% {
        transform: scale(1.1);
    }
    100% {
        transform: scale(1);
        opacity: 1;
    }
}

@keyframes floatUp {
    0% {
        opacity: 1;
        transform: translateY(0);
    }
    100% {
        opacity: 0;
        transform: translateY(-60px);
    }
}

@keyframes pulseGlow {
    0%, 100% {
        box-shadow: none;
    }
    50% {
        box-shadow: 0 0 20px rgba(46, 125, 50, 0.4);
    }
}

@keyframes spin {
    from {
        transform: rotate(0deg);
    }
    to {
        transform: rotate(360deg);
    }
}

/* --------------------------------------------------------------------------
   Animation Helper Classes
   -------------------------------------------------------------------------- */
.animate-fadeInUp {
    animation: fadeInUp 0.4s ease;
}

.animate-shakeX {
    animation: shakeX 0.5s ease;
}

.animate-popIn {
    animation: popIn 0.4s ease;
}

.animate-floatUp {
    animation: floatUp 1.2s ease forwards;
}

.animate-pulseGlow {
    animation: pulseGlow 2s ease infinite;
}

/* --------------------------------------------------------------------------
   XP Floating Animation
   -------------------------------------------------------------------------- */
.xp-float {
    position: absolute;
    color: var(--color-primary);
    font-weight: 700;
    font-size: var(--font-size-lg);
    pointer-events: none;
    animation: floatUp 1.2s ease forwards;
}

/* --------------------------------------------------------------------------
   Level-Up Banner
   -------------------------------------------------------------------------- */
.level-up-banner {
    position: fixed;
    top: 80px;
    left: 50%;
    transform: translateX(-50%);
    z-index: 2000;
    background: linear-gradient(135deg, var(--color-primary), var(--color-primary-dark));
    color: #ffffff;
    padding: 1rem 2rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-xl);
    animation: popIn 0.4s ease;
    text-align: center;
    font-weight: 600;
    font-size: var(--font-size-lg);
    white-space: nowrap;
}

.level-up-banner.dismiss {
    animation: fadeInUp 0.3s ease reverse forwards;
}

/* --------------------------------------------------------------------------
   Badge Toast
   -------------------------------------------------------------------------- */
.badge-toast {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    z-index: 2000;
    background: #ffffff;
    box-shadow: var(--shadow-lg);
    padding: 1rem 1.5rem;
    border-radius: var(--radius-lg);
    border-left: 4px solid var(--color-gold);
    animation: fadeInUp 0.4s ease;
    max-width: 320px;
}

.badge-toast .badge-toast-title {
    font-weight: 600;
    margin-bottom: 0.25rem;
}

.badge-toast .badge-toast-text {
    font-size: var(--font-size-md);
    color: var(--color-gray-600);
}

/* --------------------------------------------------------------------------
   Stats Grid
   -------------------------------------------------------------------------- */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
    gap: var(--space-md);
}

.stat-item {
    text-align: center;
    padding: var(--space-md);
    background-color: var(--color-gray-100);
    border-radius: var(--radius-md);
}

.stat-value {
    font-size: var(--font-size-4xl);
    font-weight: 700;
    color: var(--color-primary);
    line-height: 1.2;
}

.stat-label {
    font-size: var(--font-size-sm);
    color: #888888;
    margin-top: 0.2rem;
}

/* --------------------------------------------------------------------------
   Training - Mode Selection Cards
   -------------------------------------------------------------------------- */
.mode-card {
    cursor: pointer;
    border: 2px solid var(--color-gray-300);
    border-radius: var(--radius-lg);
    transition: all var(--transition-fast);
    padding: var(--space-lg);
    text-align: center;
    background: #ffffff;
}

.mode-card:hover {
    border-color: var(--color-primary);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.mode-card.active {
    border-color: var(--color-primary);
    background-color: var(--color-primary-light);
}

.mode-card .mode-icon {
    font-size: 2rem;
    margin-bottom: var(--space-sm);
}

.mode-card .mode-title {
    font-weight: 600;
    margin-bottom: 0.3rem;
}

.mode-card .mode-description {
    font-size: var(--font-size-md);
    color: var(--color-gray-600);
}

/* --------------------------------------------------------------------------
   Training - Question & Answer
   -------------------------------------------------------------------------- */
.question-text {
    font-size: var(--font-size-2xl);
    font-weight: 500;
    line-height: 1.5;
    margin-bottom: 1.2rem;
    color: var(--color-gray-900);
}

.answer-input {
    width: 100%;
    padding: 0.8rem 1rem;
    border: 2px solid var(--color-gray-300);
    border-radius: var(--radius-md);
    font-family: var(--font-family);
    font-size: var(--font-size-lg);
    color: var(--color-gray-900);
    outline: none;
    transition: border-color var(--transition-fast);
}

.answer-input:focus {
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(46, 125, 50, 0.12);
}

/* --------------------------------------------------------------------------
   Training - Multiple Choice Options
   -------------------------------------------------------------------------- */
.option-item {
    display: block;
    padding: 0.8rem 1.2rem;
    border: 2px solid var(--color-gray-300);
    border-radius: var(--radius-md);
    cursor: pointer;
    margin-bottom: 0.5rem;
    transition: all var(--transition-fast);
    background: #ffffff;
    font-size: var(--font-size-base);
}

.option-item:hover {
    border-color: var(--color-primary);
    background-color: #f9f9f9;
}

.option-item.selected {
    border-color: var(--color-primary);
    background-color: var(--color-primary-light);
}

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

/* --------------------------------------------------------------------------
   Training - Result Cards
   -------------------------------------------------------------------------- */
.result-card {
    padding: 1.2rem;
    border-radius: var(--radius-md);
    margin-bottom: var(--space-md);
}

.result-correct {
    background-color: var(--color-primary-light);
    border: 1px solid #a5d6a7;
}

.result-wrong {
    background-color: var(--color-error-light);
    border: 1px solid var(--color-error-border);
}

.result-icon {
    font-size: var(--font-size-xl);
    font-weight: 700;
}

.result-correct .result-icon {
    color: var(--color-primary);
}

.result-wrong .result-icon {
    color: var(--color-error);
}

/* --------------------------------------------------------------------------
   Hero Section (Dashboard)
   -------------------------------------------------------------------------- */
.hero {
    background: #ffffff;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    padding: var(--space-xl);
    text-align: center;
    margin-bottom: var(--space-lg);
}

.hero h1 {
    font-size: var(--font-size-3xl);
    margin-bottom: 0.3rem;
}

.hero .greeting {
    font-size: 1.2rem;
    color: var(--color-primary);
    font-weight: 500;
}

/* --------------------------------------------------------------------------
   Quick Action Grid (Dashboard)
   -------------------------------------------------------------------------- */
.action-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-md);
    margin-bottom: var(--space-lg);
}

.action-card {
    background: #ffffff;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    padding: var(--space-lg);
    border-left: 4px solid var(--color-primary);
    transition: all var(--transition-fast);
    text-decoration: none;
    color: var(--color-gray-900);
    display: block;
}

.action-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
    color: var(--color-gray-900);
}

.action-card .action-title {
    font-weight: 600;
    margin-bottom: 0.25rem;
}

.action-card .action-description {
    font-size: var(--font-size-md);
    color: var(--color-gray-600);
}

/* --------------------------------------------------------------------------
   Badge Section (Dashboard)
   -------------------------------------------------------------------------- */
.badges-section {
    display: flex;
    gap: var(--space-md);
    overflow-x: auto;
    padding-bottom: var(--space-sm);
    -webkit-overflow-scrolling: touch;
    scrollbar-width: thin;
}

.badges-section::-webkit-scrollbar {
    height: 4px;
}

.badges-section::-webkit-scrollbar-thumb {
    background: var(--color-gray-300);
    border-radius: var(--radius-pill);
}

.badge-card {
    min-width: 120px;
    text-align: center;
    background: #ffffff;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    padding: var(--space-md);
    flex-shrink: 0;
}

.badge-card .badge-icon {
    font-size: 2rem;
    margin-bottom: 0.3rem;
}

.badge-card .badge-name {
    font-size: var(--font-size-sm);
    font-weight: 500;
    color: var(--color-gray-800);
}

/* --------------------------------------------------------------------------
   Mastery Dots (Vocabulary List)
   -------------------------------------------------------------------------- */
.mastery-dot {
    width: 10px;
    height: 10px;
    border-radius: 50%;
    display: inline-block;
    margin-right: 0.3rem;
}

.mastery-dot.mastered {
    background-color: var(--color-primary);
}

.mastery-dot.learning {
    background-color: var(--color-gold);
}

.mastery-dot.new {
    background-color: var(--color-gray-300);
}

/* --------------------------------------------------------------------------
   Table Styles (Vocabulary)
   -------------------------------------------------------------------------- */
table {
    width: 100%;
    border-collapse: collapse;
}

th,
td {
    padding: 0.7rem;
    border-bottom: 1px solid #eeeeee;
    text-align: left;
}

th {
    font-size: 0.85rem;
    color: #888888;
    font-weight: 500;
}

/* --------------------------------------------------------------------------
   Empty State
   -------------------------------------------------------------------------- */
.empty-state {
    text-align: center;
    padding: var(--space-2xl) var(--space-md);
    color: #999999;
}

.empty-state p {
    margin-bottom: var(--space-md);
}

/* --------------------------------------------------------------------------
   Error Message
   -------------------------------------------------------------------------- */
.error-message {
    color: var(--color-error);
    font-size: 0.85rem;
    margin-top: var(--space-sm);
}

/* --------------------------------------------------------------------------
   Loading Spinner
   -------------------------------------------------------------------------- */
.spinner {
    width: 24px;
    height: 24px;
    border: 3px solid var(--color-gray-300);
    border-top-color: var(--color-primary);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

/* --------------------------------------------------------------------------
   Responsive Design (Mobile-First)
   -------------------------------------------------------------------------- */

/* -- Base / Mobile (< 640px) -- */
.form-row {
    flex-direction: column;
}

.action-grid {
    grid-template-columns: 1fr;
}

.nav-links {
    gap: 1rem;
}

/* -- Tablet (>= 640px) -- */
@media (min-width: 640px) {
    .form-row {
        flex-direction: row;
    }

    .action-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .stats-grid {
        grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
    }

    .nav-links {
        gap: 1.5rem;
    }
}

/* -- Desktop (>= 1024px) -- */
@media (min-width: 1024px) {
    .container {
        max-width: 900px;
    }

    .hero h1 {
        font-size: 1.8rem;
    }

    .question-text {
        font-size: 1.5rem;
    }

    .stats-grid {
        grid-template-columns: repeat(4, 1fr);
    }
}