/* ==================== CSS Variables & Design Tokens ==================== */
:root {
    /* Color Palette - Vibrant and Modern */
    --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --secondary-gradient: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    --success-gradient: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
    --warning-gradient: linear-gradient(135deg, #fa709a 0%, #fee140 100%);

    --primary-color: #667eea;
    --primary-dark: #5568d3;
    --secondary-color: #764ba2;
    --accent-color: #f5576c;
    --success-color: #00f2fe;
    --warning-color: #fee140;

    /* Neutral Colors */
    --bg-primary: #0f0f1e;
    --bg-secondary: #1a1a2e;
    --bg-tertiary: #252541;
    --text-primary: #ffffff;
    --text-secondary: #b8b8d1;
    --text-muted: #6b6b8c;

    /* Glass Effect */
    --glass-bg: rgba(255, 255, 255, 0.05);
    --glass-border: rgba(255, 255, 255, 0.1);
    --glass-shadow: 0 8px 32px 0 rgba(31, 38, 135, 0.37);

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

    /* Typography */
    --font-primary: 'Noto Sans JP', sans-serif;
    --font-secondary: 'Inter', sans-serif;

    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 20px;
    --radius-xl: 30px;

    /* Transitions */
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
}

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

body {
    font-family: var(--font-primary);
    background: var(--bg-primary);
    color: var(--text-primary);
    min-height: 100vh;
    overflow-x: hidden;
    position: relative;
}

/* Animated Background */
body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background:
        radial-gradient(circle at 20% 50%, rgba(102, 126, 234, 0.15) 0%, transparent 50%),
        radial-gradient(circle at 80% 80%, rgba(118, 75, 162, 0.15) 0%, transparent 50%),
        radial-gradient(circle at 40% 20%, rgba(245, 87, 108, 0.1) 0%, transparent 50%);
    z-index: -1;
    animation: backgroundShift 20s ease infinite;
}

@keyframes backgroundShift {

    0%,
    100% {
        opacity: 1;
        transform: scale(1);
    }

    50% {
        opacity: 0.8;
        transform: scale(1.1);
    }
}

#app {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* ==================== Typography ==================== */
h1 {
    font-size: clamp(2rem, 5vw, 3.5rem);
    font-weight: 900;
    background: var(--primary-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--spacing-md);
    line-height: 1.2;
}

h2 {
    font-size: clamp(1.5rem, 3vw, 2.5rem);
    font-weight: 700;
    margin-bottom: var(--spacing-md);
}

h3 {
    font-size: clamp(1.2rem, 2vw, 1.8rem);
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
}

p {
    line-height: 1.8;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
}

/* ==================== Glass Card Component ==================== */
.glass-card {
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    box-shadow: var(--glass-shadow);
    transition: all var(--transition-normal);
}

.glass-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 12px 40px 0 rgba(31, 38, 135, 0.5);
    border-color: rgba(255, 255, 255, 0.2);
}

/* ==================== Button Styles ==================== */
.btn {
    padding: var(--spacing-sm) var(--spacing-lg);
    border: none;
    border-radius: var(--radius-md);
    font-family: var(--font-primary);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-normal);
    position: relative;
    overflow: hidden;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-xs);
}

.btn::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 0;
    height: 0;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.2);
    transform: translate(-50%, -50%);
    transition: width 0.6s, height 0.6s;
}

.btn:hover::before {
    width: 300px;
    height: 300px;
}

.btn-primary {
    background: var(--primary-gradient);
    color: white;
    box-shadow: 0 4px 15px rgba(102, 126, 234, 0.4);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(102, 126, 234, 0.6);
}

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

.btn-secondary:hover {
    border-color: var(--primary-color);
    background: rgba(102, 126, 234, 0.1);
}

.btn-success {
    background: var(--success-gradient);
    color: white;
    box-shadow: 0 4px 15px rgba(0, 242, 254, 0.4);
}

.btn-warning {
    background: var(--warning-gradient);
    color: var(--bg-primary);
    box-shadow: 0 4px 15px rgba(254, 225, 64, 0.4);
}

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

/* ==================== Container & Layout ==================== */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-lg);
    width: 100%;
}

.section {
    padding: var(--spacing-xl) 0;
}

/* ==================== Grid System ==================== */
.grid {
    display: grid;
    gap: var(--spacing-lg);
}

.grid-2 {
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
}

.grid-3 {
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
}

.grid-4 {
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
}

/* ==================== Progress Bar ==================== */
.progress-bar {
    width: 100%;
    height: 8px;
    background: var(--bg-tertiary);
    border-radius: var(--radius-sm);
    overflow: hidden;
    position: relative;
}

.progress-fill {
    height: 100%;
    background: var(--primary-gradient);
    border-radius: var(--radius-sm);
    transition: width var(--transition-slow);
    position: relative;
    overflow: hidden;
}

.progress-fill::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    bottom: 0;
    right: 0;
    background: linear-gradient(90deg,
            transparent,
            rgba(255, 255, 255, 0.3),
            transparent);
    animation: shimmer 2s infinite;
}

@keyframes shimmer {
    0% {
        transform: translateX(-100%);
    }

    100% {
        transform: translateX(100%);
    }
}

/* ==================== Badge ==================== */
.badge {
    display: inline-flex;
    align-items: center;
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-xl);
    font-size: 0.875rem;
    font-weight: 600;
    font-family: var(--font-secondary);
}

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

.badge-success {
    background: var(--success-gradient);
    color: white;
}

.badge-warning {
    background: var(--warning-gradient);
    color: var(--bg-primary);
}

/* ==================== Timer Display ==================== */
.timer {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    font-family: var(--font-secondary);
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-primary);
}

.timer.warning {
    color: var(--accent-color);
    animation: pulse 1s infinite;
}

@keyframes pulse {

    0%,
    100% {
        opacity: 1;
    }

    50% {
        opacity: 0.6;
    }
}

/* ==================== Choice Options ==================== */
.choices {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.choice {
    background: var(--glass-bg);
    border: 2px solid var(--glass-border);
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
    cursor: pointer;
    transition: all var(--transition-fast);
    position: relative;
    overflow: hidden;
}

.choice::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    height: 100%;
    width: 4px;
    background: var(--primary-gradient);
    transform: scaleY(0);
    transition: transform var(--transition-normal);
}

.choice:hover {
    border-color: var(--primary-color);
    background: rgba(102, 126, 234, 0.1);
    transform: translateX(5px);
}

.choice:hover::before {
    transform: scaleY(1);
}

.choice.selected {
    border-color: var(--primary-color);
    background: rgba(102, 126, 234, 0.2);
}

.choice.correct {
    border-color: var(--success-color);
    background: rgba(0, 242, 254, 0.1);
}

.choice.incorrect {
    border-color: var(--accent-color);
    background: rgba(245, 87, 108, 0.1);
}

/* ==================== Stats Display ==================== */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: var(--spacing-md);
}

.stat-card {
    text-align: center;
    padding: var(--spacing-md);
}

.stat-value {
    font-size: 2.5rem;
    font-weight: 700;
    background: var(--primary-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    display: block;
    margin-bottom: var(--spacing-xs);
}

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

/* ==================== Loading Animation ==================== */
.loading {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: var(--spacing-xs);
}

.loading-dot {
    width: 12px;
    height: 12px;
    border-radius: 50%;
    background: var(--primary-gradient);
    animation: loadingBounce 1.4s infinite ease-in-out both;
}

.loading-dot:nth-child(1) {
    animation-delay: -0.32s;
}

.loading-dot:nth-child(2) {
    animation-delay: -0.16s;
}

@keyframes loadingBounce {

    0%,
    80%,
    100% {
        transform: scale(0);
    }

    40% {
        transform: scale(1);
    }
}

/* ==================== Fade In Animation ==================== */
.fade-in {
    animation: fadeIn 0.5s ease;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ==================== Responsive Design ==================== */
@media (max-width: 768px) {
    .container {
        padding: var(--spacing-md);
    }

    .section {
        padding: var(--spacing-lg) 0;
    }

    .grid-2,
    .grid-3,
    .grid-4 {
        grid-template-columns: 1fr;
    }

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

@media (max-width: 480px) {
    :root {
        --spacing-lg: 1.5rem;
        --spacing-xl: 2rem;
    }

    .glass-card {
        padding: var(--spacing-md);
    }

    .btn {
        padding: var(--spacing-sm) var(--spacing-md);
        font-size: 0.9rem;
    }
}

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

.text-left {
    text-align: left;
}

.text-right {
    text-align: right;
}

.mt-sm {
    margin-top: var(--spacing-sm);
}

.mt-md {
    margin-top: var(--spacing-md);
}

.mt-lg {
    margin-top: var(--spacing-lg);
}

.mt-xl {
    margin-top: var(--spacing-xl);
}

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

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

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

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

.flex {
    display: flex;
}

.flex-column {
    flex-direction: column;
}

.flex-center {
    justify-content: center;
    align-items: center;
}

.flex-between {
    justify-content: space-between;
    align-items: center;
}

.gap-sm {
    gap: var(--spacing-sm);
}

.gap-md {
    gap: var(--spacing-md);
}

.gap-lg {
    gap: var(--spacing-lg);
}

.hidden {
    display: none;
}

/* Quiz mode spacing to prevent navigation overlap */
.quiz-mode {
    padding-bottom: 120px;
}