:root {
    --radius: 1rem;
    --blur: 12px;
    --shadow: 0 12px 30px rgba(0, 0, 0, 0.1);
    --dark-shadow: 0 12px 30px rgba(0, 0, 0, 0.4);
    --transition: 0.3s ease-in-out;
    --font: 'Inter', system-ui, sans-serif;
}

body {
    font-family: var(--font);
    background: linear-gradient(120deg, #dbeafe, #f8fafc);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
    padding: 1rem;
    transition: var(--transition);
}

body.dark {
    background: linear-gradient(120deg, #0f172a, #1e293b);
    color: #e2e8f0;
}

.glass-card {
    background: rgba(255, 255, 255, 0.15);
    backdrop-filter: blur(var(--blur));
    border: 1px solid rgba(255, 255, 255, 0.2);
    border-radius: var(--radius);
    padding: 2rem;
    box-shadow: var(--shadow);
    transition: var(--transition);
}

.dark .glass-card {
    background: rgba(0, 0, 0, 0.15);
    border: 1px solid rgba(255, 255, 255, 0.05);
    box-shadow: var(--dark-shadow);
}

.gradient-button {
    background-size: 200% auto;
    border: none;
    border-radius: 0.75rem;
    padding: 0.75rem 1.5rem;
    font-weight: 600;
    color: #fff;
    cursor: pointer;
    transition: var(--transition);
    box-shadow: 0 6px 20px rgba(0, 0, 0, 0.15);
    display: grid;
    align-items: center;
    justify-content: center;
}

.gradient-button:hover {
    background-position: right center;
    transform: translateY(-2px);
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.25);
}

.gradient-button:focus {
    outline: none;
    box-shadow: 0 0 0 4px rgba(99, 102, 241, 0.4);
}

#classic-mode { background-image: linear-gradient(135deg, #6366f1, #8b5cf6); }

#timed-mode { background-image: linear-gradient(135deg, #f59e0b, #fbbf24); }

#custom-mode { background-image: linear-gradient(135deg, #72cf69, #4ab857); }

#high-scores { background-image: linear-gradient(135deg, #c084fc, #d8b4fe); }

#play-again { background-image: linear-gradient(135deg, #fbbf24, #fde68a); }

#back-to-menu {
    background-image: linear-gradient(135deg, #94a3b8, #64748b);
    color: #f1f5f9;
}

.dark #back-to-menu {
    background-image: linear-gradient(135deg, #475569, #334155);
}

.glowing-border-correct {
    border: 2px solid #34d399;
    box-shadow: 0 0 16px 2px #34d399aa;
}

.glowing-border-wrong {
    border: 2px solid #ef4444;
    box-shadow: 0 0 16px 2px #ef4444aa;
}

.streak-glow {
    text-shadow: 0 0 12px #ffd700cc;
    animation: pulse 1.5s ease-in-out infinite;
}

.flag-display-area {
    background: rgba(255, 255, 255, 0.07);
    padding: 2rem;
    border-radius: var(--radius);
    box-shadow: inset 0 0 8px rgba(0, 0, 0, 0.1);
    transition: var(--transition);
}

.dark .flag-display-area {
    background: rgba(0, 0, 0, 0.1);
    box-shadow: inset 0 0 8px rgba(255, 255, 255, 0.05);
}

#flag-image {
    width: 100%;
    max-height: 180px;
    object-fit: contain;
    border-radius: 0.75rem;
    box-shadow: 0 6px 20px rgba(0, 0, 0, 0.15);
    transition: var(--transition);
}

.dark #flag-image {
    box-shadow: 0 6px 20px rgba(0, 0, 0, 0.4);
}

.answer-btn.correct {
    background: linear-gradient(to right, #10b981, #34d399);
    border: none;
    color: #fff;
    box-shadow: 0 4px 16px rgba(52, 211, 153, 0.4);
}

.answer-btn.wrong {
    background: linear-gradient(to right, #dc2626, #ef4444);
    border: none;
    color: #fff;
    box-shadow: 0 4px 16px rgba(239, 68, 68, 0.4);
}

.spinner {
    border: 4px solid rgba(0, 0, 0, 0.1);
    border-left-color: #6366f1;
    border-radius: 50%;
    width: 24px;
    height: 24px;
    animation: spin 1s linear infinite;
}

.dark .spinner {
    border-color: rgba(255, 255, 255, 0.15);
    border-left-color: #a855f7;
}

@keyframes pulse {
    0%, 100% { opacity: 1; }
    
    50% { opacity: 0.6; }
    
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    
    100% { transform: rotate(360deg); }
    
}
