body{font-family:system-ui,sans-serif;background:#f5f7fa;color:#172334;max-width:64rem;margin:auto;padding:1.5rem}header,nav{display:flex;gap:1rem;flex-wrap:wrap;align-items:center}main{background:white;margin-block:2rem;padding:2rem;border-radius:1rem}a{color:#174a87}input,textarea,button{font:inherit;padding:.6rem}textarea{display:block;max-width:100%;width:34rem;height:8rem}.plain-text{white-space:pre-wrap;overflow-wrap:anywhere;line-height:1.8}table{border-collapse:collapse;width:100%}th,td{padding:.7rem;border:1px solid #b7c4d4;text-align:start}button{cursor:pointer}.lesson-list li{margin-block:1rem}pre{font-family:inherit}