* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    /* Color Palette - Vibrant and Modern */
    --primary: #6366f1;
    --primary-dark: #4f46e5;
    --primary-light: #818cf8;
    --secondary: #ec4899;
    --secondary-dark: #db2777;
    --accent: #14b8a6;
    --success: #10b981;
    --warning: #f59e0b;
    --danger: #ef4444;

    /* Gradients */
    --gradient-primary: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --gradient-success: linear-gradient(135deg, #10b981 0%, #059669 100%);
    --gradient-danger: linear-gradient(135deg, #ef4444 0%, #dc2626 100%);
    --gradient-game: linear-gradient(135deg, #667eea 0%, #764ba2 50%, #f093fb 100%);

    /* Neutral Colors */
    --bg-dark: #0f172a;
    --bg-darker: #020617;
    --text-light: #f1f5f9;
    --text-gray: #cbd5e1;
    --glass-bg: rgba(255, 255, 255, 0.1);
    --glass-border: rgba(255, 255, 255, 0.2);

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

    /* Typography */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.25rem;
    --font-size-xl: 1.5rem;
    --font-size-2xl: 2rem;
    --font-size-3xl: 3rem;

    /* Effects */
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.2);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.3);
    --shadow-glow: 0 0 20px rgba(99, 102, 241, 0.5);

    /* Border Radius */
    --radius-sm: 0.5rem;
    --radius-md: 1rem;
    --radius-lg: 1.5rem;
    --radius-full: 9999px;

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 300ms ease;
    --transition-slow: 500ms ease;
}

body {
    font-family: var(--font-family);
    background: var(--bg-darker);
    background-image: var(--gradient-game);
    background-attachment: fixed;
    color: var(--text-light);
    overflow-x: hidden;
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
}

#game-container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    padding: var(--spacing-md);
}

/* Canvas Styling */
canvas {
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    display: block;
    margin: 0 auto;
}

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

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

@keyframes slideIn {
    from {
        transform: translateX(-100%);
        opacity: 0;
    }

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

@keyframes pulse {

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

    50% {
        transform: scale(1.05);
    }
}

@keyframes glow {

    0%,
    100% {
        box-shadow: 0 0 20px rgba(99, 102, 241, 0.5);
    }

    50% {
        box-shadow: 0 0 40px rgba(99, 102, 241, 0.8);
    }
}

@keyframes float {

    0%,
    100% {
        transform: translateY(0px);
    }

    50% {
        transform: translateY(-10px);
    }
}

@keyframes confetti {
    0% {
        transform: translateY(0) rotate(0deg);
        opacity: 1;
    }

    100% {
        transform: translateY(100vh) rotate(720deg);
        opacity: 0;
    }
}

/* Responsive Design */
@media (max-width: 768px) {
    :root {
        --font-size-3xl: 2rem;
        --font-size-2xl: 1.5rem;
        --font-size-xl: 1.25rem;
    }

    #game-container {
        padding: var(--spacing-sm);
    }
}

@media (max-width: 480px) {
    :root {
        --font-size-3xl: 1.75rem;
        --font-size-2xl: 1.25rem;
    }
}

/* Utility Classes for Phaser Text Styling */
.glass-effect {
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    border: 1px solid var(--glass-border);
}

.gradient-text {
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* 3D Flash Card Styles */
#flashcard-overlay {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    z-index: 1000;
    perspective: 1500px;
    pointer-events: none;
}

#flashcard-overlay * {
    pointer-events: auto;
}

.card-scene {
    width: 700px;
    height: 500px;
    position: relative;
}

.card-3d {
    width: 100%;
    height: 100%;
    position: relative;
    transform-style: preserve-3d;
    transition: transform 0.8s cubic-bezier(0.68, -0.55, 0.265, 1.55);
    cursor: pointer;
}

.card-3d.flipped {
    transform: rotateY(180deg);
}

.card-face {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    box-shadow:
        0 20px 60px rgba(0, 0, 0, 0.3),
        0 0 0 1px rgba(255, 255, 255, 0.1) inset,
        0 0 40px rgba(99, 102, 241, 0.2);
    background: linear-gradient(135deg, #ffffff 0%, #f8fafc 100%);
    display: flex;
    flex-direction: column;
    justify-content: space-between;
}

.card-front {
    transform: rotateY(0deg);
}

.card-back {
    transform: rotateY(180deg);
    background: linear-gradient(135deg, #f0f9ff 0%, #e0f2fe 100%);
}

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-md);
}

.difficulty-badge {
    padding: var(--spacing-xs) var(--spacing-md);
    border-radius: var(--radius-full);
    font-weight: bold;
    font-size: var(--font-size-sm);
    color: white;
    text-transform: uppercase;
}

.difficulty-easy {
    background: var(--success);
}

.difficulty-medium {
    background: var(--warning);
}

.difficulty-hard {
    background: var(--danger);
}

.question-number {
    font-size: var(--font-size-sm);
    color: var(--text-gray);
    font-weight: 600;
}

.card-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    justify-content: center;
    gap: var(--spacing-lg);
}

.question-text {
    font-size: var(--font-size-xl);
    font-weight: 700;
    color: var(--bg-dark);
    text-align: center;
    line-height: 1.5;
}

.answer-input-container {
    position: relative;
}

.answer-input {
    width: 100%;
    padding: var(--spacing-md) var(--spacing-lg);
    font-size: var(--font-size-lg);
    font-family: var(--font-family);
    border: 3px solid var(--primary);
    border-radius: var(--radius-md);
    background: white;
    color: var(--bg-dark);
    transition: all var(--transition-base);
    outline: none;
}

.answer-input:focus {
    border-color: var(--primary-dark);
    box-shadow: 0 0 0 4px rgba(99, 102, 241, 0.1);
    transform: scale(1.02);
}

.answer-input::placeholder {
    color: var(--text-gray);
    opacity: 0.6;
}

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

.card-button {
    padding: var(--spacing-md) var(--spacing-xl);
    font-size: var(--font-size-lg);
    font-weight: 700;
    font-family: var(--font-family);
    border: none;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-base);
    box-shadow: var(--shadow-md);
}

.flip-button {
    background: var(--gradient-primary);
    color: white;
    min-width: 200px;
}

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

.flip-button:active {
    transform: translateY(0);
}

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

.correct-button {
    background: var(--gradient-success);
    color: white;
    min-width: 150px;
}

.correct-button:hover {
    transform: translateY(-2px) scale(1.05);
}

.incorrect-button {
    background: var(--gradient-danger);
    color: white;
    min-width: 150px;
}

.incorrect-button:hover {
    transform: translateY(-2px) scale(1.05);
}

.next-button {
    background: var(--primary);
    color: white;
    min-width: 200px;
}

.next-button:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
}

.answer-section {
    text-align: center;
}

.answer-label {
    font-size: var(--font-size-base);
    color: var(--text-gray);
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-bottom: var(--spacing-sm);
}

.answer-text {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    color: var(--primary);
    margin-bottom: var(--spacing-md);
}

.explanation-text {
    font-size: var(--font-size-base);
    color: var(--bg-dark);
    line-height: 1.6;
    padding: var(--spacing-md);
    background: rgba(255, 255, 255, 0.5);
    border-radius: var(--radius-sm);
}

.verification-result {
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    font-weight: 600;
    text-align: center;
    margin-bottom: var(--spacing-md);
}

.verification-correct {
    background: rgba(16, 185, 129, 0.1);
    color: var(--success);
    border: 2px solid var(--success);
}

.verification-incorrect {
    background: rgba(239, 68, 68, 0.1);
    color: var(--danger);
    border: 2px solid var(--danger);
}

.flip-hint {
    text-align: center;
    color: var(--text-gray);
    font-size: var(--font-size-sm);
    opacity: 0.7;
    margin-top: var(--spacing-sm);
}

/* Loading Spinner for AI Verification */
.ai-loading {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-md);
    padding: var(--spacing-lg);
}

.spinner {
    width: 50px;
    height: 50px;
    border: 4px solid rgba(99, 102, 241, 0.1);
    border-top: 4px solid var(--primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    0% {
        transform: rotate(0deg);
    }

    100% {
        transform: rotate(360deg);
    }
}

.ai-loading-text {
    font-size: var(--font-size-lg);
    color: var(--primary);
    font-weight: 600;
    animation: pulse 1.5s ease-in-out infinite;
}

@keyframes pulse {

    0%,
    100% {
        opacity: 1;
    }

    50% {
        opacity: 0.5;
    }
}

/* Responsive adjustments for 3D cards */
@media (max-width: 768px) {
    .card-scene {
        width: 90vw;
        max-width: 600px;
        height: 450px;
    }

    .question-text {
        font-size: var(--font-size-lg);
    }

    .answer-text {
        font-size: var(--font-size-xl);
    }
}