*{box-sizing:border-box}body{margin:0;font-family:Inter,sans-serif;background:#f3f4f6;display:flex;justify-content:center;align-items:center;height:100vh}
.app{width:min(700px,95vw);height:85vh;background:#fff;border-radius:16px;display:flex;flex-direction:column;box-shadow:0 8px 30px rgba(0,0,0,.08);overflow:hidden}
header{padding:18px;background:#2563eb;color:#fff;font-size:20px;font-weight:600}
#chatbox{flex:1;overflow:auto;padding:20px;background:#fafafa}
.bot,.user{padding:12px 16px;border-radius:14px;max-width:75%;margin:10px 0;animation:fade .2s}
.bot{background:#ececec}
.user{background:#dbeafe;margin-left:auto}
form{display:flex;border-top:1px solid #ddd}
input{flex:1;border:none;padding:16px;font-size:15px;outline:none}
button{width:110px;border:none;background:#2563eb;color:#fff;cursor:pointer}
button:hover{background:#1d4ed8}
.watermark{position:fixed;right:18px;bottom:18px;opacity:.2;font-size:13px;font-weight:600;pointer-events:none}
@keyframes fade{from{opacity:0;transform:translateY(8px)}to{opacity:1;transform:none}}