:root {
  --ink: #102e35;
  --muted: #63777b;
  --paper: #f4f7f6;
  --card: rgba(255, 255, 255, 0.9);
  --teal: #137f73;
  --line: rgba(16, 46, 53, 0.12);
}

* {
  box-sizing: border-box;
}

html {
  background: var(--paper);
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--ink);
  background:
    radial-gradient(circle at 18% 8%, rgba(55, 176, 159, 0.18), transparent 34rem),
    radial-gradient(circle at 90% 25%, rgba(255, 151, 117, 0.1), transparent 30rem),
    var(--paper);
  font-family:
    -apple-system, BlinkMacSystemFont, "Hiragino Sans", "Yu Gothic UI",
    "Noto Sans JP", sans-serif;
  -webkit-font-smoothing: antialiased;
}

[lang="en"] {
  font-family: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Helvetica Neue", sans-serif;
}

main {
  width: min(100% - 32px, 980px);
  margin: 0 auto;
  padding: 76px 0 44px;
}

.hero {
  padding: 30px 8px 66px;
}

.app-icon {
  display: block;
  margin-bottom: 26px;
  border-radius: 20px;
  box-shadow: 0 14px 32px rgba(16, 46, 53, 0.12);
}

.eyebrow {
  margin: 0 0 10px;
  color: var(--teal);
  font-size: 0.82rem;
  font-weight: 750;
  letter-spacing: 0.12em;
}

h1 {
  max-width: 780px;
  margin: 0;
  font-size: clamp(2.6rem, 7vw, 5.4rem);
  line-height: 1.04;
  letter-spacing: -0.055em;
}

.title-en {
  margin: 10px 0 0;
  color: var(--teal);
  font-size: clamp(1.1rem, 2.4vw, 1.45rem);
  font-weight: 680;
}

.lead {
  max-width: 700px;
  margin: 30px 0 22px;
  color: var(--muted);
  font-size: clamp(1.1rem, 2.4vw, 1.5rem);
  line-height: 1.9;
}

.lead strong {
  color: var(--ink);
  font-weight: 680;
}

.lead-en {
  max-width: 700px;
  margin: 0 0 24px;
  color: var(--muted);
  line-height: 1.75;
}

nav,
.principles {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

nav {
  margin-bottom: 16px;
}

nav a,
.principles span {
  padding: 10px 15px;
  border: 1px solid rgba(19, 127, 115, 0.16);
  border-radius: 999px;
  color: var(--teal);
  background: rgba(255, 255, 255, 0.62);
  font-size: 0.86rem;
  font-weight: 680;
  text-decoration: none;
}

nav a:hover,
nav a:focus-visible {
  background: #fff;
  outline: 2px solid rgba(19, 127, 115, 0.25);
  outline-offset: 2px;
}

.card {
  margin-bottom: 24px;
  padding: clamp(26px, 5vw, 56px);
  border: 1px solid rgba(255, 255, 255, 0.85);
  border-radius: 32px;
  background: var(--card);
  box-shadow: 0 24px 80px rgba(30, 75, 73, 0.08);
  backdrop-filter: blur(18px);
}

.section-heading {
  display: flex;
  align-items: baseline;
  gap: 16px;
  margin-bottom: 36px;
}

.section-heading > span {
  color: var(--teal);
  font-size: 0.78rem;
  font-weight: 760;
  letter-spacing: 0.12em;
}

.section-heading div > p {
  margin: 6px 0 0;
  color: var(--muted);
  font-size: 0.9rem;
  font-weight: 600;
}

h2 {
  margin: 0;
  font-size: clamp(1.55rem, 3vw, 2.25rem);
  letter-spacing: -0.035em;
}

.grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0 38px;
}

article {
  padding: 26px 0;
  border-top: 1px solid var(--line);
}

h3 {
  margin: 0 0 12px;
  font-size: 1.02rem;
}

h3.english {
  margin-top: 24px;
  color: var(--teal);
  font-size: 0.92rem;
}

article p,
details p,
.contact p {
  margin: 0;
  color: var(--muted);
  line-height: 1.85;
}

.contact {
  margin: 0 0 28px;
  padding: 22px;
  border-radius: 20px;
  background: rgba(19, 127, 115, 0.07);
}

.contact a {
  display: inline-block;
  margin-top: 12px;
  color: var(--teal);
  font-size: 1.05rem;
  font-weight: 720;
}

.faq {
  border-bottom: 1px solid var(--line);
}

details {
  border-top: 1px solid var(--line);
}

summary {
  position: relative;
  padding: 23px 42px 23px 0;
  cursor: pointer;
  list-style: none;
  font-weight: 680;
}

summary::-webkit-details-marker {
  display: none;
}

summary::after {
  position: absolute;
  top: 50%;
  right: 6px;
  content: "＋";
  color: var(--teal);
  font-size: 1.3rem;
  transform: translateY(-50%);
}

details[open] summary::after {
  content: "−";
}

details p {
  max-width: 760px;
  padding: 0 40px 24px 0;
}

footer {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 10px 24px;
  padding: 34px 8px;
  color: var(--muted);
  font-size: 0.86rem;
}

footer p {
  margin: 0;
}

footer .small {
  flex-basis: 100%;
  font-size: 0.76rem;
  opacity: 0.72;
}

@media (max-width: 680px) {
  main {
    padding-top: 36px;
  }

  .hero {
    padding-bottom: 48px;
  }

  .grid {
    grid-template-columns: 1fr;
  }

  .card {
    border-radius: 24px;
  }
}

@media (prefers-color-scheme: dark) {
  :root {
    --ink: #eaf5f2;
    --muted: #9db0ae;
    --paper: #071513;
    --card: rgba(18, 37, 34, 0.92);
    --teal: #62d4c2;
    --line: rgba(228, 245, 241, 0.12);
  }

  .card {
    border-color: rgba(255, 255, 255, 0.06);
  }

  nav a,
  .principles span {
    background: rgba(255, 255, 255, 0.04);
  }
}