.vert-toggle {
  position: fixed;
  right: 16px;
  bottom: 16px;
  z-index: 80;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: var(--paper);
  border: 1px solid var(--paper-edge);
  color: var(--ink);
  font-family: var(--kai-zh);
  font-size: 12px;
  line-height: 1.1;
  cursor: pointer;
  box-shadow: var(--shadow-1);
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
}

.vert-toggle:hover { transform: scale(1.06); background: var(--paper-deep); }
.vert-toggle .vt-v { display: none; }
body.vertical-mode .vert-toggle .vt-h { display: none; }
body.vertical-mode .vert-toggle .vt-v { display: block; }

body.vertical-mode .reader-layout {
  display: block;
  max-width: none;
  overflow-x: auto;
  overflow-y: hidden;
}

body.vertical-mode .reader-main {
  writing-mode: vertical-rl;
  -webkit-writing-mode: vertical-rl;
  text-orientation: upright;
  height: calc(100vh - 84px);
  min-height: 620px;
  max-width: none;
  padding: 32px 28px;
}

body.vertical-mode .reader-aside { display: none; }
body.vertical-mode .lesson-block,
body.vertical-mode .summary-block {
  margin: 0 20px 0 0;
  padding: 18px 12px;
}

body.vertical-mode .lesson-block p,
body.vertical-mode .summary-block p,
body.vertical-mode .lesson-block li,
body.vertical-mode .summary-block li {
  line-height: 2.05;
  letter-spacing: 0.06em;
}

body.vertical-mode .nav-bar,
body.vertical-mode .page-head,
body.vertical-mode .site-foot,
body.vertical-mode .basic-banner {
  writing-mode: horizontal-tb;
  -webkit-writing-mode: horizontal-tb;
}

@media (max-width: 760px) {
  .vert-toggle { width: 40px; height: 40px; right: 10px; bottom: 10px; font-size: 11px; }
}