*{box-sizing:border-box}body{margin:0;font-family:Arial,sans-serif;background:#0b0f14;color:#fff}.app{height:100vh;display:flex;flex-direction:column;max-width:1000px;margin:auto}header{height:64px;display:flex;align-items:center;justify-content:space-between;padding:0 22px;border-bottom:1px solid #222;background:#0d1219}header b{font-size:21px}header span{font-size:13px;color:#69e69b}main{flex:1;overflow:auto;padding:28px 20px}.welcome{text-align:center;margin-top:18vh;color:#aab3c0}.welcome h1{color:#fff}.msg{max-width:780px;margin:0 auto 18px;padding:14px 16px;border-radius:14px;line-height:1.55;white-space:pre-wrap}.user{background:#1c2a3a}.assistant{background:#121922}.error{background:#4a1717}form{display:flex;gap:10px;padding:14px 18px;border-top:1px solid #222;background:#0d1219}textarea{flex:1;resize:none;max-height:160px;border:1px solid #303844;border-radius:13px;background:#151b23;color:#fff;padding:14px;font:inherit;outline:none}button{width:50px;border:0;border-radius:13px;background:#fff;color:#000;font-size:21px;cursor:pointer}button:disabled{opacity:.5}@media(max-width:600px){main{padding:18px 12px}form{padding:10px}}