/* YT Furigana site — sumi ink + vermillion editorial */
:root {
  --sumi: #1c1917;
  --sumi-soft: #44403c;
  --paper: #f3efe6;
  --paper-deep: #e7e0d2;
  --vermilion: #c23b22;
  --vermilion-deep: #9a2e1b;
  --line: color-mix(in oklab, var(--sumi) 14%, transparent);
  --display: "Shippori Mincho", "Hiragino Mincho ProN", serif;
  --body: "Zen Kaku Gothic New", "Hiragino Sans", sans-serif;
  --max: 68rem;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--sumi);
  background:
    radial-gradient(1200px 500px at 10% -10%, color-mix(in oklab, var(--vermilion) 10%, transparent), transparent 60%),
    linear-gradient(180deg, var(--paper) 0%, var(--paper-deep) 100%);
  font-family: var(--body);
  line-height: 1.7;
}

a {
  color: var(--vermilion-deep);
  text-underline-offset: 0.18em;
}

a:hover {
  color: var(--vermilion);
}

.wrap {
  width: min(100% - 2rem, var(--max));
  margin-inline: auto;
}

.site-header {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 1rem;
  padding: 1.25rem 0 0.5rem;
}

.brand {
  font-family: var(--display);
  font-weight: 600;
  font-size: 1.15rem;
  letter-spacing: 0.04em;
  text-decoration: none;
  color: var(--sumi);
}

.nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.9rem 1.25rem;
  font-size: 0.92rem;
}

.nav a {
  text-decoration: none;
  color: var(--sumi-soft);
}

.nav a:hover {
  color: var(--vermilion);
}

.hero {
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: clamp(1.5rem, 4vw, 3.5rem);
  align-items: end;
  padding: clamp(2.5rem, 8vw, 5.5rem) 0 3rem;
  border-bottom: 1px solid var(--line);
}

@media (max-width: 860px) {
  .hero {
    grid-template-columns: 1fr;
  }
}

.hero h1 {
  margin: 0;
  font-family: var(--display);
  font-weight: 600;
  font-size: clamp(2.4rem, 7vw, 4.6rem);
  line-height: 1.15;
  letter-spacing: 0.02em;
}

.hero .lead {
  margin: 1.1rem 0 0;
  max-width: 34rem;
  font-size: 1.05rem;
  color: var(--sumi-soft);
}

.hero-aside {
  border-left: 3px solid var(--vermilion);
  padding: 0.2rem 0 0.2rem 1.1rem;
  font-family: var(--display);
  font-size: 1.15rem;
  line-height: 1.8;
}

.cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-top: 1.75rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.72rem 1.15rem;
  border-radius: 999px;
  border: 1px solid var(--sumi);
  background: var(--sumi);
  color: var(--paper);
  text-decoration: none;
  font-size: 0.95rem;
  font-weight: 600;
  transition: transform 0.25s cubic-bezier(0.16, 1, 0.3, 1), background 0.2s ease;
}

.btn:hover {
  transform: translateY(-2px);
  color: var(--paper);
  background: var(--vermilion);
  border-color: var(--vermilion);
}

.btn.ghost {
  background: transparent;
  color: var(--sumi);
}

.btn.ghost:hover {
  background: color-mix(in oklab, var(--vermilion) 12%, transparent);
  color: var(--vermilion-deep);
  border-color: var(--vermilion);
}

.section {
  padding: clamp(2.5rem, 6vw, 4.5rem) 0;
  border-bottom: 1px solid var(--line);
}

.section h2 {
  margin: 0 0 0.75rem;
  font-family: var(--display);
  font-size: clamp(1.6rem, 3vw, 2.2rem);
  font-weight: 600;
}

.section .sub {
  margin: 0 0 1.5rem;
  color: var(--sumi-soft);
  max-width: 38rem;
}

.plan-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1.25rem;
}

@media (max-width: 720px) {
  .plan-grid {
    grid-template-columns: 1fr;
  }
}

.plan {
  padding: 1.35rem 1.4rem 1.5rem;
  border: 1px solid var(--line);
  background: color-mix(in oklab, white 55%, var(--paper));
}

.plan.featured {
  border-color: color-mix(in oklab, var(--vermilion) 55%, var(--line));
  box-shadow: 0 18px 40px color-mix(in oklab, var(--sumi) 8%, transparent);
}

.plan h3 {
  margin: 0;
  font-family: var(--display);
  font-size: 1.35rem;
}

.plan .price {
  margin: 0.35rem 0 0.9rem;
  font-size: 1.8rem;
  font-family: var(--display);
}

.plan ul {
  margin: 0;
  padding-left: 1.1rem;
  color: var(--sumi-soft);
}

.plan li + li {
  margin-top: 0.35rem;
}

.prose {
  max-width: 42rem;
}

.prose h1 {
  font-family: var(--display);
  font-size: clamp(1.8rem, 4vw, 2.6rem);
  margin: 2rem 0 1rem;
}

.prose h2 {
  font-family: var(--display);
  font-size: 1.35rem;
  margin: 2rem 0 0.6rem;
}

.prose p,
.prose li {
  color: var(--sumi-soft);
}

.site-footer {
  padding: 2rem 0 3rem;
  color: var(--sumi-soft);
  font-size: 0.88rem;
}

.site-footer nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.85rem 1.2rem;
  margin-bottom: 0.85rem;
}

.ruby-demo {
  font-family: var(--display);
  font-size: clamp(1.4rem, 3vw, 1.9rem);
  line-height: 2.1;
}

.ruby-demo ruby {
  ruby-align: center;
}

.ruby-demo rt {
  font-size: 0.45em;
  color: var(--vermilion-deep);
}

.fade-up {
  animation: fadeUp 0.8s cubic-bezier(0.16, 1, 0.3, 1) both;
}

.fade-up.delay {
  animation-delay: 0.12s;
}

@keyframes fadeUp {
  from {
    opacity: 0;
    transform: translateY(16px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@media (prefers-reduced-motion: reduce) {
  .fade-up,
  .btn {
    animation: none;
    transition: none;
  }
}

.field-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  margin-top: 1rem;
}

.field-row input {
  flex: 1 1 14rem;
  padding: 0.7rem 0.85rem;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: white;
  font: inherit;
}

.status {
  margin-top: 0.85rem;
  font-size: 0.92rem;
}

.status.ok {
  color: #166534;
}

.status.err {
  color: var(--vermilion-deep);
}

.site-footer .trademark-note {
  font-size: 0.85rem;
  margin-top: 0.75rem;
  color: var(--muted, #5c5348);
  max-width: 42rem;
  line-height: 1.55;
}

code.key {
  display: inline-block;
  margin-top: 0.5rem;
  padding: 0.45rem 0.65rem;
  background: white;
  border: 1px dashed var(--line);
  border-radius: 8px;
  font-size: 0.9rem;
  word-break: break-all;
}