:root {
  --bg: #f5f5f7;
  --panel: #ffffff;
  --text: #1d1d1f;
  --muted: #6e6e73;
  --line: #e5e5ea;
  --accent: #0071e3;
  --radius: clamp(14px, 2vw, 24px);
}
* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "SF Pro Text", Inter, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
}
.layout {
  min-height: 100vh;
  display: grid;
  grid-template-columns: 300px 1fr;
  gap: 14px;
  padding: 14px;
}
.sidebar, .main {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}
.sidebar { padding: 14px; display:flex; flex-direction:column; }
.brand { display:flex; justify-content:space-between; align-items:center; }
.brand h1 { margin:0; font-size:20px; }
.side-actions { margin: 12px 0; display:flex; gap:8px; }
.chat-list { overflow:auto; display:flex; flex-direction:column; gap:8px; }
.chat-item {
  display:grid;
  grid-template-columns: 1fr auto;
  gap:6px;
  align-items:center;
  padding:10px;
  border:1px solid var(--line);
  border-radius: 12px;
  background:#fff;
}
.chat-item.active { border-color:#b9d8ff; background:#f2f8ff; }
.chat-item .title { cursor:pointer; font-size:14px; }
.chat-item .actions { display:flex; gap:4px; }
button {
  border: 0;
  border-radius: 12px;
  padding: 10px 14px;
  background: var(--accent);
  color: #fff;
  font-weight: 600;
  cursor: pointer;
}
button.ghost { background: #f2f2f7; color:#111; }
button.tiny { padding: 6px 8px; font-size: 12px; border-radius: 8px; }
button[disabled] { opacity:0.6; cursor:not-allowed; }
.main { display:flex; flex-direction:column; padding:14px; }
.topbar { display:flex; justify-content:space-between; align-items:flex-start; margin-bottom:8px; }
.topbar h2 { margin:0; font-size:18px; }
.muted { color:var(--muted); margin:4px 0 0; font-size:12px; }
.chat {
  flex:1;
  min-height: 50vh;
  max-height: 64vh;
  overflow:auto;
  padding: 8px;
  border:1px solid var(--line);
  border-radius: calc(var(--radius) - 6px);
  background:#fcfcfd;
}
.msg-wrap { margin:10px 0; max-width:78%; }
.msg-wrap.user-wrap { margin-left:auto; }
.msg { padding:10px 12px; border-radius:14px; white-space:pre-wrap; }
.user { background:#e8f2ff; }
.assistant { background:#f2f2f7; }
.system { background:#fff7e6; color:#5b4700; max-width:100%; }
.msg-actions { display:flex; gap:6px; margin-top:5px; }
.msg-actions button { padding:4px 8px; font-size:11px; border-radius:8px; background:#eef0f4; color:#1d1d1f; }
.msg-actions button:hover { background:#e1e5ea; }
.typing { color:var(--muted); }
.attachments { display:flex; flex-wrap:wrap; gap:8px; margin:10px 0 2px; }
.attachments.dragover { outline:2px dashed #9dc6ff; border-radius:12px; padding:8px; background:#f7fbff; }
.file-chip {
  display:flex; gap:6px; align-items:center;
  padding:8px 10px; border:1px solid var(--line); border-radius:10px; background:#fff;
  font-size:12px;
}
.composer { display:grid; grid-template-columns:auto 1fr auto; gap:10px; margin-top:10px; }
.upload-btn {
  display:inline-flex; align-items:center; justify-content:center;
  padding: 10px 12px; border-radius:12px; border:1px solid var(--line); background:#fff; cursor:pointer;
}
#prompt {
  width:100%; resize:vertical; min-height:46px; max-height:170px;
  border:1px solid var(--line); border-radius:12px; padding:10px; font:inherit;
}
dialog {
  border:1px solid var(--line); border-radius:16px; width:min(520px,95vw); background:#fff; color:var(--text);
}
label { display:block; margin:10px 0; }
.switch-row { display:flex; align-items:center; justify-content:space-between; gap:12px; }
.switch-row input { width:auto; margin-top:0; }
input {
  width:100%; margin-top:6px; padding:10px; border-radius:10px; border:1px solid var(--line);
}
.hint { color:var(--muted); font-size:12px; }
.actions { display:flex; gap:8px; justify-content:flex-end; }

@media (max-width: 920px) {
  .layout { grid-template-columns: 1fr; }
  .sidebar { max-height: 36vh; }
  .chat { max-height: 54vh; }
}