:root{
  --bg:#0b0f14;
  --panel:#0f1622;
  --panel2:#0c121c;
  --text:#e6edf3;
  --muted:#9fb0c0;
  --border:#1f2a37;
  --primary:#2f81f7;
  --bubble:#111b2a;
  --bubble2:#0e1726;
  --shadow: 0 10px 30px rgba(0,0,0,.35);
  --radius: 16px;
  --radius2: 12px;
  --font: ui-sans-serif, system-ui, -apple-system, "Segoe UI", "Noto Sans JP", Arial, sans-serif;
}

*{box-sizing:border-box}
html,body{height:100%}
body{
  margin:0;
  background: radial-gradient(1200px 800px at 20% 10%, #12233c 0%, var(--bg) 55%);
  color:var(--text);
  font-family:var(--font);
}

.app{
  height:100vh;
  display:grid;
  grid-template-columns: 320px 1fr;
}

.sidebar{
  background: linear-gradient(180deg, rgba(255,255,255,.04), rgba(255,255,255,0));
  border-right:1px solid var(--border);
  padding:18px;
  display:flex;
  flex-direction:column;
  gap:14px;
}

.brand{
  display:flex;
  gap:12px;
  align-items:center;
  padding:10px 10px;
  border:1px solid var(--border);
  border-radius: var(--radius);
  background: rgba(15,22,34,.55);
  box-shadow: var(--shadow);
}
.brand-dot{
  width:12px;height:12px;border-radius:999px;background:var(--primary);
  box-shadow: 0 0 0 6px rgba(47,129,247,.14);
}
.brand-title{font-weight:700; letter-spacing:.2px}
.brand-sub{font-size:12px; color:var(--muted); margin-top:2px}

.section-title{font-size:12px; color:var(--muted); margin-top:6px}
.thread-list{
  display:flex; flex-direction:column; gap:8px;
  overflow:auto; padding-right:4px; flex:1;
}
.thread{
  padding:10px 12px;
  border:1px solid var(--border);
  border-radius: var(--radius2);
  background: rgba(15,22,34,.35);
  cursor:pointer;
}
.thread:hover{border-color:#2c3b4e}
.thread.active{border-color: rgba(47,129,247,.7); background: rgba(47,129,247,.12)}
.thread-title{font-size:14px; font-weight:600}
.thread-meta{font-size:12px; color:var(--muted); margin-top:2px}

.footer-note{
  font-size:12px;
  color:var(--muted);
  opacity:.9;
}

.main{
  display:grid;
  grid-template-rows: 58px 1fr auto;
  min-width:0;
}

.topbar{
  display:flex;
  align-items:center;
  justify-content:space-between;
  padding:12px 18px;
  border-bottom:1px solid var(--border);
  background: rgba(15,22,34,.35);
  backdrop-filter: blur(10px);
}
.topbar-title{font-weight:700; min-width:0; overflow:hidden; text-overflow:ellipsis; white-space:nowrap}
.topbar-actions{display:flex; gap:10px}

.chat{
  padding: 18px;
  overflow:auto;
  display:flex;
  flex-direction:column;
  gap:14px;
}

.msg{
  max-width: 880px;
  border:1px solid var(--border);
  border-radius: var(--radius);
  padding: 12px 14px;
  background: rgba(17,27,42,.55);
  box-shadow: var(--shadow);
  line-height:1.55;
  white-space:pre-wrap;
  word-break:break-word;
}
.msg.user{
  align-self:flex-end;
  background: rgba(47,129,247,.14);
  border-color: rgba(47,129,247,.35);
}
.msg.assistant{
  align-self:flex-start;
  background: rgba(17,27,42,.55);
}

.composer{
  border-top:1px solid var(--border);
  background: rgba(15,22,34,.35);
  padding: 12px 18px;
  display:flex;
  gap:10px;
  align-items:flex-end;
}
textarea{
  width:100%;
  resize:none;
  max-height: 180px;
  padding: 12px 12px;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: rgba(12,18,28,.8);
  color: var(--text);
  outline:none;
  font-family: var(--font);
  font-size: 14px;
}
textarea:focus{border-color: rgba(47,129,247,.6)}
.btn{
  border:1px solid var(--border);
  border-radius: 999px;
  padding: 10px 14px;
  font-weight: 700;
  cursor:pointer;
  background: rgba(255,255,255,.04);
  color: var(--text);
}
.btn:hover{border-color:#2c3b4e}
.btn-ghost{background: rgba(255,255,255,.03)}
.btn-primary{
  border-color: rgba(47,129,247,.6);
  background: rgba(47,129,247,.18);
}
.btn-primary:hover{border-color: rgba(47,129,247,.9)}

@media (max-width: 900px){
  .app{grid-template-columns: 1fr}
  .sidebar{display:none}
}