.app {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: 240px 1fr;
  height: 100vh;
  padding: 18px;
  gap: 18px;
}

.sidebar,
.stage {
  background: var(--glass);
  backdrop-filter: blur(22px) saturate(140%);
  -webkit-backdrop-filter: blur(22px) saturate(140%);
  border: 1px solid rgba(255, 255, 255, 0.12);
  box-shadow: var(--shadow);
  border-radius: 28px;
}

.sidebar {
  display: flex;
  flex-direction: column;
  padding: 22px 18px;
  gap: 16px;
  min-height: 0;          /* 允许在 grid 单元格内收缩，避免把底部按钮挤出 */
}

.brand,
.new-chat,
.sidebar-foot {
  flex-shrink: 0;         /* 品牌区/新对话按钮/底部按钮永远不被压缩 */
}

.brand {
  display: flex;
  gap: 12px;
  align-items: center;
}

.logo {
  width: 46px;
  height: 46px;
  border-radius: 16px;
  display: grid;
  place-items: center;
  background: linear-gradient(145deg, var(--neon-orange), var(--neon-yellow));
  color: #2a1c10;
  font-size: 26px;
  font-weight: 600;
  box-shadow: 0 0 24px rgba(255, 156, 64, 0.35);
}

.brand-name {
  font-family: var(--font-display);
  font-size: 17px;
  letter-spacing: 0.04em;
  color: var(--ink);
  font-weight: 500;
}

.brand-en {
  font-family: var(--font-display);
  font-size: 18px;
  letter-spacing: 0.02em;
  color: var(--ink);
}

.brand-zh {
  font-size: 12px;
  color: var(--muted);
}

.new-chat {
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 12px 14px;
  border-radius: 16px;
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid var(--line);
  color: var(--ink);
  transition: 0.2s;
}

.new-chat:hover {
  background: rgba(255, 255, 255, 0.12);
  border-color: rgba(255, 156, 64, 0.4);
}

.history {
  flex: 1;
  overflow: auto;
  min-height: 0;          /* 会话列表超过空间时才出现滚动条 */
}

.history-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  margin-bottom: 8px;
}

.history-head .section-label {
  margin-bottom: 0;
}

.clear-history {
  border: none;
  background: transparent;
  color: var(--muted);
  font-size: 12px;
  padding: 2px 6px;
  border-radius: 8px;
  transition: 0.15s;
}

.clear-history:hover {
  color: var(--ink-soft);
  background: rgba(255, 255, 255, 0.08);
}

.section-label {
  font-size: 12px;
  color: var(--muted);
  margin-bottom: 8px;
}

#historyList {
  list-style: none;
  display: grid;
  gap: 6px;
}

#historyList button {
  width: 100%;
  text-align: left;
  padding: 8px 10px;
  border-radius: 12px;
  font-size: 13px;
  color: var(--ink-soft);
  transition: 0.15s;
}

#historyList button:hover {
  background: rgba(255, 255, 255, 0.08);
  color: var(--ink);
}

#historyList button.active {
  background: rgba(255, 156, 64, 0.14);
  color: var(--neon-orange);
  box-shadow: inset 0 0 0 1px rgba(255, 156, 64, 0.35);
}

.sidebar-foot button {
  width: 100%;
  padding: 10px;
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.06);
  color: var(--ink-soft);
  transition: 0.15s;
}

.sidebar-foot button:hover {
  background: rgba(255, 255, 255, 0.12);
  color: var(--ink);
}

.stage {
  display: grid;
  grid-template-rows: auto 1fr auto;
  min-width: 0;
  min-height: 0;          /* 允许在 .app 的 grid 行内收缩 */
}

.topbar {
  display: flex;
  align-items: center;
  padding: 14px 28px 0;
  min-height: 16px;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  padding: 14px 28px 0;
  min-height: 16px;
}

.lang-switch {
  position: relative;
}

.lang-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 12px;
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid var(--line);
  color: var(--ink-soft);
  font-size: 13px;
  transition: 0.15s;
}

.lang-btn:hover,
.lang-btn[aria-expanded="true"] {
  background: rgba(255, 255, 255, 0.12);
  color: var(--ink);
  border-color: rgba(255, 156, 64, 0.35);
}

.lang-chevron {
  opacity: 0.7;
}

.lang-menu {
  position: absolute;
  top: calc(100% + 6px);
  right: 0;
  min-width: 120px;
  padding: 6px;
  border-radius: 14px;
  background: var(--glass-strong);
  border: 1px solid rgba(255, 255, 255, 0.14);
  box-shadow: var(--shadow);
  z-index: 20;
}

.lang-menu[hidden] {
  display: none;
}

.lang-menu button {
  display: block;
  width: 100%;
  text-align: left;
  padding: 8px 10px;
  border-radius: 10px;
  font-size: 13px;
  color: var(--ink-soft);
  transition: 0.15s;
}

.lang-menu button:hover,
.lang-menu button.active {
  background: rgba(255, 156, 64, 0.14);
  color: var(--neon-orange);
}

@media (max-width: 960px) {
  body { overflow: auto; }
  .app {
    grid-template-columns: 1fr;
    height: auto;
    min-height: 100vh;
  }
  .sidebar { order: 2; }
}