:root {
    --primary: #2563eb;
    --success: #059669;
    --error: #dc2626;
    --bg: #f8fafc;
    --text: #1e293b;
}

body { font-family: system-ui, -apple-system, sans-serif; background: var(--bg); color: var(--text); line-height: 1.5; margin: 0; padding: 20px; }
.container { max-width: 800px; margin: 0 auto; }
.card { background: white; padding: 2rem; border-radius: 12px; box-shadow: 0 4px 6px -1px rgb(0 0 0 / 0.1); margin-top: 2rem; }
.hidden { display: none; }

button { 
    display: block; width: 100%; text-align: left; padding: 1rem; margin: 0.5rem 0;
    border: 1px solid #e2e8f0; border-radius: 8px; background: white; cursor: pointer; transition: all 0.2s;
}

button:hover:not(:disabled) { background: #f1f5f9; border-color: var(--primary); }
button.correct { background: var(--success) !important; color: white; border-color: var(--success); }
button.wrong { background: var(--error) !important; color: white; border-color: var(--error); }

#next-btn { 
    background: var(--primary); color: white; text-align: center; margin-top: 2rem; font-weight: 600;
}

#feedback { margin-top: 1rem; font-weight: bold; padding: 1rem; border-radius: 8px; }
#meta { color: #64748b; font-size: 0.875rem; margin-bottom: 0.5rem; }