:root {
  --bg: #f6f7f9;
  --surface: #ffffff;
  --text: #1f2328;
  --muted: #6b7280;
  --border: #e2e5ea;
  --user-bg: #2563eb;
  --user-text: #ffffff;
  --assistant-bg: #ffffff;
  --accent: #2563eb;
  --danger: #dc2626;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #101216;
    --surface: #171a20;
    --text: #e7eaee;
    --muted: #9aa3ad;
    --border: #262b33;
    --assistant-bg: #1d2129;
  }
}

* { box-sizing: border-box; }

html, body { height: 100%; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  background: var(--bg);
  color: var(--text);
}

.app {
  display: flex;
  flex-direction: column;
  height: 100dvh;
  max-width: 860px;
  margin: 0 auto;
}

.topbar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px 14px;
  padding: 12px 16px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
}

.brand { font-size: 17px; font-weight: 700; margin-right: auto; }

.controls {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
}

.model-label { font-size: 13px; color: var(--muted); }

select {
  max-width: 240px;
  padding: 7px 8px;
  font-size: 14px;
  color: var(--text);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
}

.btn {
  padding: 8px 14px;
  font-size: 14px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
  cursor: pointer;
}
.btn:disabled { opacity: 0.5; cursor: not-allowed; }
.btn-ghost:hover { border-color: var(--muted); }
.btn-send { background: var(--accent); border-color: var(--accent); color: #fff; font-weight: 600; }
.btn-stop { color: var(--danger); border-color: var(--danger); }

.chat-list {
  flex: 1;
  overflow-y: auto;
  padding: 16px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  -webkit-overflow-scrolling: touch;
}

.empty { margin: auto; text-align: center; color: var(--muted); padding: 24px; }
.empty-title { font-size: 18px; font-weight: 600; color: var(--text); margin: 0 0 6px; }
.empty-sub { margin: 0; font-size: 14px; }

.msg {
  max-width: 85%;
  padding: 10px 14px;
  border-radius: 14px;
  line-height: 1.6;
  font-size: 15px;
  white-space: pre-wrap;
  word-break: break-word;
}
.msg.user {
  align-self: flex-end;
  background: var(--user-bg);
  color: var(--user-text);
  border-bottom-right-radius: 4px;
}
.msg.assistant {
  align-self: flex-start;
  background: var(--assistant-bg);
  border: 1px solid var(--border);
  border-bottom-left-radius: 4px;
}
.msg.error {
  align-self: center;
  max-width: 95%;
  background: transparent;
  border: 1px solid var(--danger);
  color: var(--danger);
  font-size: 14px;
}
.msg .cursor { display: inline-block; animation: blink 1s steps(1) infinite; }
@keyframes blink { 50% { opacity: 0; } }

.composer-wrap {
  background: var(--surface);
  border-top: 1px solid var(--border);
  padding: 10px 12px calc(10px + env(safe-area-inset-bottom));
}

.status { font-size: 13px; color: var(--muted); padding: 0 4px 8px; }

.composer { display: flex; gap: 8px; align-items: flex-end; }

textarea {
  flex: 1;
  resize: none;
  max-height: 140px;
  padding: 10px 12px;
  font: inherit;
  font-size: 15px;
  color: var(--text);
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 10px;
  outline: none;
}
textarea:focus { border-color: var(--accent); }

@media (max-width: 600px) {
  .brand { width: 100%; margin-right: 0; }
  select { max-width: 200px; flex: 1; }
  .msg { max-width: 92%; font-size: 14.5px; }
  .chat-list { padding: 12px; }
}