:root {
  --ink: #0e1114;
  --ink-soft: #3d4550;
  --mist: #f4f7f9;
  --wave: #c41e2a;
  --line: rgba(14, 17, 20, 0.12);
  --font-display: "Instrument Serif", "Noto Serif SC", Georgia, serif;
  --font-cn: "Noto Serif SC", "Instrument Serif", Georgia, serif;
  --font-body: "Noto Sans SC", system-ui, sans-serif;
}
* {
  box-sizing: border-box;
}
body {
  margin: 0;
  min-height: 100dvh;
  background:
    radial-gradient(120% 80% at 50% -10%, #ffffff 0%, transparent 55%),
    linear-gradient(180deg, #eef3f6 0%, var(--mist) 42%, #e4ebf0 100%);
  color: var(--ink);
  font-family: var(--font-body);
}
.wrap {
  max-width: 42rem;
  margin: 0 auto;
  padding: 1.25rem 1rem 2.5rem;
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  text-decoration: none;
  color: inherit;
  margin-bottom: 1.25rem;
}
.brand img {
  width: 2.25rem;
  height: 2.25rem;
  object-fit: contain;
}
.brand span {
  font-family: var(--font-display);
  font-size: 1.15rem;
  letter-spacing: 0.02em;
}
h1 {
  font-family: var(--font-cn);
  font-size: clamp(1.55rem, 4.5vw, 2rem);
  font-weight: 700;
  line-height: 1.25;
  margin: 0 0 0.45rem;
}
.lead {
  margin: 0 0 1.25rem;
  color: var(--ink-soft);
  font-size: 0.98rem;
  line-height: 1.55;
}
.tutorial-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 0.65rem;
}
.tutorial-item {
  border: 1px solid var(--line);
  border-radius: 12px;
  background: #fff;
  overflow: hidden;
}
.tutorial-item summary {
  list-style: none;
  cursor: pointer;
  padding: 0.95rem 1rem;
  font-size: 1.05rem;
  font-weight: 700;
  line-height: 1.4;
  color: var(--ink);
}
.tutorial-item summary::-webkit-details-marker {
  display: none;
}
.tutorial-item summary::after {
  content: "›";
  float: right;
  color: var(--wave);
  font-weight: 400;
  font-size: 1.25rem;
  line-height: 1.2;
}
.tutorial-item[open] summary::after {
  content: "⌄";
}
.tutorial-panel {
  padding: 0 1rem 1rem;
}
.player {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: 12px;
  overflow: hidden;
  background: #0e1114;
  aspect-ratio: 9 / 16;
  max-height: min(72dvh, 640px);
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: center;
}
.player--wide {
  aspect-ratio: 16 / 9;
  max-height: min(56dvh, 480px);
}
.player video,
.player iframe {
  display: block;
  width: 100%;
  height: 100%;
  border: 0;
  background: #0e1114;
}
.player-soon {
  margin: 0;
  padding: 1.25rem;
  color: #e8eef2;
  font-size: 0.95rem;
  text-align: center;
  line-height: 1.5;
}
.lead a {
  color: var(--wave);
  font-weight: 700;
}
.foot {
  margin-top: 2rem;
  padding-top: 1rem;
  border-top: 1px solid var(--line);
  font-size: 0.85rem;
  color: var(--ink-soft);
}
.foot a {
  color: var(--wave);
}