:root {
  color-scheme: light;
  font-family: "Hiragino Sans", "Yu Gothic UI", "Yu Gothic", system-ui, sans-serif;
  color: #173b52;
  background: #f4f7f8;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-width: 320px;
  background:
    radial-gradient(circle at 85% 0%, #dff5f6 0, transparent 30rem),
    #f4f7f8;
}

a { color: inherit; text-decoration: none; }

.site-shell { width: min(1080px, calc(100% - 32px)); margin: 0 auto; padding: 30px 0 28px; }
.site-header { display: flex; align-items: center; justify-content: space-between; }
.brand { color: #12364b; font-size: 1.35rem; font-weight: 900; letter-spacing: .06em; }
.brand span { color: #087c86; }
.subject-pill { border: 1px solid #b8dfe2; border-radius: 999px; padding: 7px 13px; color: #087c86; background: #effbfc; font-size: .8rem; font-weight: 800; }

.hero { padding: clamp(58px, 10vw, 108px) 0 68px; max-width: 700px; }
.eyebrow, .section-kicker { margin: 0 0 12px; color: #087c86; font-size: .78rem; font-weight: 900; letter-spacing: .12em; }
h1, h2, h3, p { margin-top: 0; }
h1 { margin-bottom: 20px; color: #12364b; font-size: clamp(2.5rem, 7vw, 5.4rem); line-height: 1.08; letter-spacing: -.05em; }
h1 span { color: #087c86; }
.hero-copy { max-width: 530px; margin-bottom: 0; color: #496373; font-size: 1.08rem; line-height: 1.8; }

.unit-heading { display: flex; align-items: end; justify-content: space-between; gap: 20px; margin-bottom: 18px; }
.unit-heading h2 { margin-bottom: 0; color: #12364b; font-size: clamp(1.5rem, 3vw, 2.15rem); }
.unit-progress { margin: 0 0 5px; color: #71848d; font-size: .87rem; }

.simulator-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
.simulator-card {
  display: flex;
  flex-direction: column;
  min-height: 280px;
  border: 1px solid #d8e3e7;
  border-radius: 18px;
  background: rgba(255, 255, 255, .95);
  box-shadow: 0 12px 30px rgba(29, 63, 78, .08);
  overflow: hidden;
}
.simulator-card.featured { transition: transform .18s ease, box-shadow .18s ease; }
.simulator-card.featured:hover { transform: translateY(-4px); box-shadow: 0 16px 34px rgba(29, 63, 78, .14); }
.card-number { padding: 16px 18px 0; color: #8ca5af; font-size: .8rem; font-weight: 900; letter-spacing: .1em; }
.card-body { display: flex; flex: 1; flex-direction: column; padding: 16px 18px 20px; }
.card-label { margin-bottom: 8px; color: #087c86; font-size: .78rem; font-weight: 900; letter-spacing: .08em; }
.card-body h3 { margin-bottom: 10px; color: #173b52; font-size: 1.2rem; line-height: 1.45; }
.card-body p:not(.card-label) { margin-bottom: 18px; color: #607783; font-size: .9rem; line-height: 1.7; }
.card-link { margin-top: auto; color: #087c86; font-size: .86rem; font-weight: 850; }
.card-link span { display: inline-block; margin-left: 5px; transition: transform .18s ease; }
.featured:hover .card-link span { transform: translateX(4px); }
.coming-soon { border-style: dashed; background: rgba(248, 251, 252, .7); box-shadow: none; }
.coming-soon .card-body h3 { color: #496373; }
.coming-label { margin-top: auto; color: #8ca5af; font-size: .84rem; font-weight: 800; }

.how-to { margin-top: 80px; border-top: 1px solid #d8e3e7; padding-top: 28px; }
.how-to h2 { margin-bottom: 22px; color: #12364b; font-size: 1.45rem; }
.steps { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; }
.step { display: flex; align-items: center; gap: 12px; border-radius: 12px; padding: 15px; background: #eaf7f8; }
.step span { color: #087c86; font-size: .78rem; font-weight: 900; }
.step p { margin: 0; color: #315461; font-weight: 750; }
footer { padding-top: 55px; color: #71848d; font-size: .8rem; text-align: center; }

@media (max-width: 820px) {
  .simulator-grid { grid-template-columns: 1fr 1fr; }
  .coming-soon { grid-column: span 2; min-height: 210px; }
}

@media (max-width: 560px) {
  .site-shell { width: min(100% - 22px, 1080px); padding-top: 22px; }
  .hero { padding: 70px 0 58px; }
  .unit-heading { align-items: start; flex-direction: column; gap: 6px; }
  .simulator-grid, .steps { grid-template-columns: 1fr; }
  .coming-soon { grid-column: auto; }
}

html { scroll-behavior: smooth; scroll-padding-top: 24px; }
.site-shell { width: min(1200px, calc(100% - 48px)); }
.site-header { gap: 24px; padding-bottom: 22px; border-bottom: 1px solid #d8e3e7; }
.site-header nav { display: flex; gap: 26px; flex-wrap: wrap; font-size: .88rem; font-weight: 700; }
a:focus-visible, summary:focus-visible { outline: 3px solid #c58220; outline-offset: 5px; }
.site-header nav a:hover { color: #087c86; text-decoration: underline; }
.hero { max-width: none; display: grid; grid-template-columns: 1fr 1fr; gap: 28px; align-items: center; padding: 64px 0 70px; }
h1 { font-size: clamp(2rem, 3.5vw, 3.4rem); line-height: 1.3; letter-spacing: -.04em; }
.hero-copy { font-size: 1rem; }
.hero-image { margin: 0; transform: rotate(1deg); }
.hero-image img { width: 100%; height: auto; display: block; border-radius: 24px; box-shadow: 0 18px 50px #1f5e5714; }
.hero-image figcaption { margin-top: 14px; text-align: center; font-size: .8rem; color: #526e76; }
.primary-link { display: inline-flex; gap: 25px; margin-top: 26px; padding: 17px 22px; border-radius: 10px; color: white; background: #087c86; font-weight: 800; }
.primary-link:hover { background: #075b65; }
.hero-note { font-size: .8rem; color: #58727d; margin: 12px 0 0; }
.card-image { width: 100%; height: 195px; object-fit: cover; display: block; }
.volume-preview { height: 195px; flex-shrink: 0; background: #edf2ed; display: flex; gap: 18px; align-items: center; justify-content: center; }
.volume-preview span { width: 35px; height: 35px; background: #ebbd72; border: 2px solid #a3804e; border-radius: 5px; }
.volume-preview span:nth-child(2) { width: 52px; height: 52px; }
.volume-preview span:nth-child(3) { width: 74px; height: 74px; }
.about-panel { display: grid; grid-template-columns: 1fr 1fr; gap: 48px; margin-top: 66px; padding: 40px; background: #e6f1ec; border-radius: 20px; }
.about-panel h2 { font-size: clamp(1.5rem, 2.3vw, 2rem); line-height: 1.55; }
.about-panel p { line-height: 1.9; }
.teacher-badge { display: inline-block; padding: 9px 14px; border-radius: 20px; background: #fff; color: #246c57; font-size: .85rem; font-weight: 750; }
.about-note { font-size: .85rem; color: #4f6862; margin-bottom: 0; }
.how-to { margin-top: 58px; }
.usage-notes { display: grid; grid-template-columns: 1fr 1fr; gap: 32px; margin: 24px 0; line-height: 1.9; color: #496373; }
.usage-notes strong { color: #087c86; }
details { padding: 18px 0; border-top: 1px solid #d8e3e7; }
summary { cursor: pointer; font-weight: 700; }
details p { margin: 14px 0 0; line-height: 1.8; }
footer { margin-top: 45px; border-top: 1px solid #d8e3e7; padding-top: 30px; }
footer .brand { display: inline-block; margin-bottom: 14px; }
@media (max-width: 820px) {
  .hero { grid-template-columns: 1fr; padding-top: 42px; }
  .hero-image { max-width: 600px; width: 100%; margin: auto; }
  .coming-soon { grid-column: auto; }
  .about-panel { grid-template-columns: 1fr; gap: 20px; }
}
@media (max-width: 560px) {
  .site-shell { width: calc(100% - 28px); }
  .site-header { align-items: flex-start; flex-direction: column; gap: 16px; }
  .site-header nav { gap: 14px; font-size: .8rem; }
  .about-panel { padding: 25px; }
  .usage-notes { grid-template-columns: 1fr; gap: 0; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .simulator-card.featured, .card-link span { transition: none; }
}

/* Keep catalog navigation usable when a narrow screen wraps the menu. */
@media (max-width: 820px) {
  .site-header nav { row-gap: 4px; }
  .site-header nav a { display: inline-flex; align-items: center; min-height: 44px; min-width: 44px; }
}