:root{ --bg:#f7f8fb; --card:#fff; --accent:#2563eb; --text:#111; --muted:#64748b; --line:#e6e9ef }
*{box-sizing:border-box;font-family:system-ui,-apple-system,Segoe UI,Roboto,'Helvetica Neue',Arial}
body{margin:0;background:var(--bg);color:var(--text);display:flex;align-items:center;justify-content:center;height:100vh}
main{background:var(--card);padding:24px;border-radius:10px;box-shadow:0 6px 24px rgba(16,24,40,.08);width:320px}
h1{margin:0 0 12px;font-size:20px}
label{display:block;margin-bottom:10px;font-size:14px}
input,textarea{width:100%;padding:8px 10px;border:1px solid var(--line);border-radius:6px;margin-top:6px}
textarea{resize:vertical;line-height:1.6}
button,.nav-button{background:var(--accent);color:#fff;border:none;padding:10px 12px;border-radius:8px;cursor:pointer;width:100%;display:inline-block;text-align:center;text-decoration:none}
button:disabled,textarea:disabled{opacity:.65;cursor:not-allowed}
.msg{color:#b91c1c;margin-top:8px}
a{color:var(--accent)}
.nav-button{margin:10px 0}
.text-link{font-size:14px;text-decoration:none;white-space:nowrap}
.chat-page{align-items:stretch;height:100vh;padding:16px}
.chat-app{width:min(880px,100%);height:calc(100vh - 32px);display:flex;flex-direction:column;padding:0;overflow:hidden}
.chat-header{display:flex;align-items:flex-start;justify-content:space-between;gap:16px;padding:18px 20px;border-bottom:1px solid var(--line)}
.chat-header h1{margin-bottom:4px}
.chat-header p{margin:0;color:var(--muted);font-size:14px}
.messages{flex:1;overflow:auto;padding:20px;background:#f9fafb}
.bubble{max-width:76%;margin:0 0 12px;padding:12px 14px;border-radius:8px;border:1px solid var(--line);background:#fff}
.bubble-user{margin-left:auto;background:#eff6ff;border-color:#bfdbfe}
.bubble-assistant{margin-right:auto}
.bubble-label{color:var(--muted);font-size:12px;font-weight:700;margin-bottom:6px}
.bubble p{margin:0;line-height:1.7;white-space:pre-wrap;word-break:break-word}
.chat-form{display:grid;grid-template-columns:1fr 120px;gap:10px;padding:16px 20px;border-top:1px solid var(--line);background:#fff}
.chat-form textarea{margin:0;min-height:48px}
.chat-form button{height:48px}
.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}

@media (max-width: 640px){
  .chat-page{padding:0}
  .chat-app{height:100vh;border-radius:0}
  .bubble{max-width:92%}
  .chat-form{grid-template-columns:1fr}
}