:root{
  --bg:#0f1216; --panel:#171b22; --panel2:#1e242d; --line:#2a313c;
  --text:#e8edf4; --muted:#8b97a8; --accent:#4f8cff; --accent2:#38d39f;
  --user:#243244; --radius:16px;
}
*{box-sizing:border-box;-webkit-tap-highlight-color:transparent}
html,body{margin:0;height:100%}
body{
  background:var(--bg);color:var(--text);
  font-family:"Segoe UI",system-ui,-apple-system,Roboto,sans-serif;
  display:flex;flex-direction:column;height:100dvh;
}

/* header */
.top{
  display:flex;align-items:center;justify-content:space-between;
  padding:12px 18px;border-bottom:1px solid var(--line);background:var(--panel);
}
.brand{font-weight:800;font-size:18px}
.brand span{color:var(--accent);font-weight:600}
.model{font-size:12.5px;color:var(--muted);display:flex;align-items:center;gap:7px}
.dot{width:8px;height:8px;border-radius:50%;background:#c04b4b;display:inline-block}
.dot.ok{background:var(--accent2);box-shadow:0 0 8px var(--accent2)}

/* chat area */
.chat{flex:1;overflow-y:auto;padding:22px 0 12px}
.chat>*{max-width:760px;margin:0 auto;padding:0 18px}
.welcome{text-align:center;color:var(--muted);margin-top:12vh}
.welcome h1{color:var(--text);font-size:30px;margin:0 0 8px}
.welcome p{font-size:15px;max-width:440px;margin:0 auto}

.msg{margin:0 auto 20px;display:flex;flex-direction:column;gap:6px}
.msg .who{font-size:12px;color:var(--muted);font-weight:700;letter-spacing:.3px}
.bubble{
  padding:13px 16px;border-radius:var(--radius);line-height:1.55;font-size:15px;
  white-space:pre-wrap;word-wrap:break-word;
}
.msg.user{align-items:flex-end}
.msg.user .bubble{background:var(--user);border-bottom-right-radius:4px;max-width:85%}
.msg.bot .bubble{background:var(--panel);border:1px solid var(--line);border-bottom-left-radius:4px}

/* reasoning (thinking) collapsible */
.think{
  background:var(--panel2);border:1px solid var(--line);border-radius:12px;
  font-size:13px;color:var(--muted);overflow:hidden;margin-bottom:2px;
}
.think summary{
  cursor:pointer;padding:9px 13px;user-select:none;list-style:none;
  display:flex;align-items:center;gap:8px;font-weight:600;
}
.think summary::-webkit-details-marker{display:none}
.think summary .spin{width:12px;height:12px;border:2px solid var(--line);border-top-color:var(--accent);border-radius:50%;animation:sp .8s linear infinite}
.think[open] summary .spin{display:none}
.think .body{padding:0 13px 11px;white-space:pre-wrap;line-height:1.5;max-height:280px;overflow-y:auto;opacity:.85}
@keyframes sp{to{transform:rotate(360deg)}}

.cursor{display:inline-block;width:8px;height:15px;background:var(--accent);
  vertical-align:text-bottom;animation:blink 1s steps(2) infinite;margin-left:1px}
@keyframes blink{0%,50%{opacity:1}50.1%,100%{opacity:0}}

/* composer */
.composer{
  display:flex;gap:10px;align-items:flex-end;max-width:760px;width:100%;
  margin:0 auto;padding:12px 18px 18px;
}
.composer textarea{
  flex:1;resize:none;background:var(--panel);color:var(--text);
  border:1px solid var(--line);border-radius:14px;padding:13px 15px;
  font-size:15px;font-family:inherit;max-height:180px;line-height:1.4;
}
.composer textarea:focus{outline:none;border-color:var(--accent)}
.composer button{
  flex:none;width:46px;height:46px;border-radius:12px;border:none;cursor:pointer;
  background:var(--accent);color:#fff;font-size:19px;transition:.15s;
}
.composer button:disabled{opacity:.4;cursor:default}
.composer button:not(:disabled):active{transform:scale(.92)}
.think-toggle{flex:none;display:flex;align-items:center;justify-content:center;
  width:46px;height:46px;border-radius:12px;background:var(--panel);border:1px solid var(--line);
  cursor:pointer;font-size:19px;user-select:none;filter:grayscale(1) opacity(.5);transition:.15s}
.think-toggle:has(input:checked){filter:none;border-color:var(--accent2);background:#12241d}
.think-toggle input{display:none}
.err{color:#ff8080;font-size:13px}

/* login */
.login{position:fixed;inset:0;background:var(--bg);z-index:100;display:flex;align-items:center;justify-content:center}
.login.hidden{display:none}
.login-card{background:var(--panel);border:1px solid var(--line);border-radius:20px;padding:34px 30px;width:340px;max-width:90vw;text-align:center}
.brand-big{font-size:26px;font-weight:800;margin-bottom:6px}
.brand-big span{color:var(--accent);font-weight:600}
.login-card p{color:var(--muted);font-size:14px;margin:8px 0 18px}
.login-card input{width:100%;padding:13px 15px;border-radius:12px;border:1px solid var(--line);
  background:var(--panel2);color:var(--text);font-size:15px;font-family:inherit;margin-bottom:12px;text-align:center}
.login-card input:focus{outline:none;border-color:var(--accent)}
.login-card button{width:100%;padding:13px;border:none;border-radius:12px;background:var(--accent);
  color:#fff;font-size:16px;font-weight:700;cursor:pointer}
.login-card button:active{transform:scale(.98)}