:root{
  --bg:#fff;
  --fg:#0b0b0b;
  --muted:#6b6b6b;
  --accent:#111827;
  --ai-bg:#f3f4f6;
  --user-bg:#111827;
  --user-text:#fff;
  font-family: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, "Noto Sans", "Helvetica Neue", Arial;
  -webkit-font-smoothing:antialiased;
  -moz-osx-font-smoothing:grayscale;
}

*{box-sizing:border-box}
html,body,#chat{height:100%}
body{
  margin:0;
  background:#f3f4f6;
  color:var(--fg);
  display:flex;
  align-items:stretch;
  justify-content:center;
  padding:24px;
}

.app{
  width:100%;
  max-width:760px;
  display:flex;
  flex-direction:column;
  gap:12px;
  height:100%;
  background:#fff;
  border-radius:16px;
  box-shadow:0 10px 30px rgba(15,15,15,0.08);
  padding:20px;
  max-height:90vh;
  overflow:hidden;
}

.header{
  padding:12px 12px 6px;
}
.header-top{
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap:12px;
}
.title{margin:0;font-weight:700;letter-spacing:-0.02em;font-size:20px}
.sub{margin:4px 0 0;color:var(--muted);font-size:13px}
.controls{display:flex;gap:8px;align-items:center}

.chat{
  background:transparent;
  padding:14px;
  border-radius:12px;
  overflow:auto;
  flex:1;
  display:flex;
  flex-direction:column;
  gap:10px;
  scroll-behavior:smooth;
}

.msg{
  max-width:78%;
  padding:12px 14px;
  border-radius:12px;
  line-height:1.4;
  box-shadow:0 1px 0 rgba(0,0,0,0.03);
  font-size:15px;
  word-break:break-word;
}

.msg.ai{
  background:var(--ai-bg);
  align-self:flex-start;
  color:var(--fg);
  border-top-left-radius:6px;
}

.msg.user{
  background:var(--user-bg);
  color:var(--user-text);
  align-self:flex-end;
  border-top-right-radius:6px;
}

.meta{
  display:flex;
  gap:8px;
  align-items:center;
  font-size:12px;
  color:var(--muted);
  margin-bottom:6px;
}

.composer{
  display:flex;
  gap:8px;
  align-items:end;
  border-top:1px solid #eee;
  padding-top:10px;
}

.input{
  flex:1;
  padding:10px 12px;
  font-size:15px;
  border:1px solid #e6e6e6;
  border-radius:8px;
  resize:none;
  min-height:44px;
  max-height:140px;
}

.send{
  background:var(--accent);
  color:#fff;
  border:none;
  padding:10px 14px;
  border-radius:8px;
  font-weight:600;
  cursor:pointer;
  height:44px;
}

.send:active{transform:translateY(1px)}

.footer{
  color:var(--muted);
  font-size:13px;
  padding:8px 12px;
  border-top:1px solid #f1f1f1;
}

.model-switch{
  margin-top:10px;
  display:flex;
  gap:8px;
  align-items:center;
}
.chip{
  background:#f7f7f8;
  border:1px solid #e6e6e6;
  padding:8px 12px;
  border-radius:10px;
  cursor:pointer;
  font-size:13px;
}
.chip[aria-pressed="true"]{
  background:var(--accent);
  color:#fff;
  border-color:transparent;
}
.model-select{
  font-size:13px;
  padding:6px 8px;
  border-radius:8px;
  border:1px solid #e6e6e6;
}