/* The language switch: a quiet "EN" / "中" at the bottom-right end of the page that
   only looks like a button under the pointer, opening a two-item menu upward. */
.lang-corner { position: relative; display: inline-flex; font-family: var(--font-sans); }
.lang-button { display: block; min-width: 32px; height: 28px; padding: 0 9px; border: 0; border-radius: 8px;
  background: transparent; color: var(--text-tertiary); font: 500 12px/28px var(--font-sans); letter-spacing: 0.02em;
  cursor: pointer; transition: background var(--duration-fast) var(--ease-standard), box-shadow var(--duration-fast) var(--ease-standard), color var(--duration-fast) var(--ease-standard); }
.lang-button:hover, .lang-button[aria-expanded="true"] { background: var(--surface-card); color: var(--text-secondary); box-shadow: var(--shadow-card-hover); }
.lang-button:focus-visible { outline: none; box-shadow: var(--shadow-focus); }
.lang-menu { position: absolute; right: 0; bottom: calc(100% + 6px); z-index: 40; min-width: 128px; padding: 4px; border: 1px solid var(--border-subtle);
  border-radius: 10px; background: var(--surface-card); box-shadow: var(--shadow-dropdown); }
.lang-menu[hidden] { display: none; }
.lang-menu button { display: flex; align-items: center; justify-content: space-between; gap: 12px; width: 100%; padding: 8px 10px;
  border: 0; border-radius: 6px; background: transparent; color: var(--text-primary); font: 400 13px/1.2 var(--font-sans); text-align: left; cursor: pointer; }
.lang-menu button:hover, .lang-menu button:focus-visible { outline: none; background: var(--surface-hover); }
.lang-menu svg { width: 14px; height: 14px; fill: none; stroke: var(--text-secondary); stroke-width: 1.8; stroke-linecap: round; stroke-linejoin: round; visibility: hidden; }
.lang-menu [aria-checked="true"] svg { visibility: visible; }