:root {
  --bg: #f5f7fb;
  --card: #ffffff;
  --text: #14213d;
  --muted: #5c6f8a;
  --line: rgba(20, 33, 61, 0.1);
  --brand: #1f6feb;
  --brand-dark: #0b3c7a;
  --radius: 18px;
  --shadow: 0 12px 30px rgba(20, 33, 61, 0.12);
  --font: "Noto Sans JP", system-ui, -apple-system, sans-serif;
  --bg-image: url("/assets/img/bg-snow-1.svg");
  --bg-overlay: 0.25;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: var(--font);
  color: var(--text);
  background:
    radial-gradient(1200px 600px at 10% -10%, rgba(31, 111, 235, 0.18), transparent 55%),
    radial-gradient(900px 500px at 90% 10%, rgba(11, 60, 122, 0.14), transparent 60%),
    linear-gradient(180deg, #f7f9ff, #e8efff);
  background-color: var(--bg);
  position: relative;
  min-height: 100%;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  background-image: var(--bg-image);
  background-size: cover;
  background-position: center;
  opacity: var(--bg-overlay);
  transition: opacity 0.6s ease;
  z-index: -2;
  pointer-events: none;
}

body.bg-switching::before {
  opacity: 0.05;
}

body[data-theme="dark"] {
  --bg: #050b1a;
  --card: rgba(8, 16, 34, 0.92);
  --text: #e5ecff;
  --muted: #9fb1d1;
  --line: rgba(148, 174, 216, 0.2);
  --shadow: 0 16px 40px rgba(2, 6, 18, 0.5);
  --bg-overlay: 0.18;
  background:
    radial-gradient(1200px 600px at 10% -10%, rgba(31, 111, 235, 0.25), transparent 55%),
    radial-gradient(900px 500px at 90% 10%, rgba(7, 25, 62, 0.45), transparent 60%),
    linear-gradient(180deg, #060b1d, #101a32);
}

img {
  max-width: 100%;
  display: block;
}

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

.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 20px;
}

.narrow {
  max-width: 680px;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  background: rgba(255, 255, 255, 0.92);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(10px);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 16px 0;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
}

.brand-logo {
  width: 44px;
  height: 44px;
  border-radius: 14px;
  object-fit: contain;
  background: #fff;
  border: 1px solid var(--line);
  padding: 6px;
}

.brand-text {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.brand-title {
  font-size: 18px;
  font-weight: 800;
}

.brand-sub {
  font-size: 12px;
  color: var(--muted);
}

.header-actions {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.theme-toggle {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: rgba(255, 255, 255, 0.8);
  font-size: 12px;
  font-weight: 700;
}

body[data-theme="dark"] .theme-toggle {
  background: rgba(12, 20, 40, 0.8);
}

.hero {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 24px;
  padding: 32px 20px;
  align-items: center;
}

.hero--full {
  display: block;
  padding: 0;
}

.hero-media {
  border-radius: var(--radius);
  overflow: hidden;
  background: #fff;
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
}

.hero-media--full {
  width: 100vw;
  margin-left: calc(50% - 50vw);
  margin-right: calc(50% - 50vw);
  border-radius: 0;
  border-left: none;
  border-right: none;
}

.hero-media--full img {
  width: 100%;
  height: auto;
}

.hero-media--full video {
  width: 100%;
  height: auto;
  display: block;
}

.hero-copy {
  background: #fff;
  border-radius: var(--radius);
  padding: 24px;
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
}

.hero-actions {
  display: flex;
  gap: 12px;
  margin-top: 18px;
  flex-wrap: wrap;
}

.notice-card {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
  padding: 20px;
  border-radius: var(--radius);
  border: 1px solid var(--line);
  background: linear-gradient(135deg, #ffffff 0%, #eef4ff 100%);
  box-shadow: var(--shadow);
}

.notice-content {
  display: flex;
  align-items: flex-start;
  gap: 16px;
}

.notice-icon {
  width: 48px;
  height: 48px;
  border-radius: 16px;
  display: grid;
  place-items: center;
  background: rgba(31, 111, 235, 0.12);
  border: 1px solid rgba(31, 111, 235, 0.25);
}

.notice-icon svg {
  width: 26px;
  height: 26px;
  fill: var(--brand-dark);
}

.notice-card h2 {
  margin: 8px 0 6px;
}

.concept-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(0, 0.95fr);
  gap: 0;
  align-items: center;
}

.concept-copy {
  background: #fff;
  border-radius: var(--radius) 0 0 var(--radius);
  padding: 24px;
  border: 1px solid var(--line);
  border-right: none;
  box-shadow: var(--shadow);
}

.concept-media {
  border-radius: 0 var(--radius) var(--radius) 0;
  overflow: hidden;
  border: 1px solid var(--line);
  border-left: none;
  box-shadow: var(--shadow);
  background: #fff;
}

.concept-media img {
  width: 100%;
  min-height: 260px;
  height: 100%;
  object-fit: cover;
}

.concept-icons {
  margin-top: 18px;
  display: grid;
  gap: 12px;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
}

.concept-icon {
  display: flex;
  gap: 10px;
  align-items: center;
  padding: 10px 12px;
  border-radius: 14px;
  border: 1px solid var(--line);
  background: rgba(31, 111, 235, 0.08);
  font-size: 12px;
  font-weight: 700;
}

.concept-icon svg {
  width: 22px;
  height: 22px;
  fill: var(--brand-dark);
}

.fade-section {
  opacity: 0;
  transform: translateY(18px);
  transition: opacity 0.8s ease, transform 0.8s ease;
}

.fade-section.is-visible {
  opacity: 1;
  transform: translateY(0);
}

.section {
  padding: 20px 0 40px;
}

.section-head h1,
.section-head h2 {
  margin: 0 0 8px;
}

.section-head {
  margin-bottom: 16px;
}

.pill {
  display: inline-flex;
  padding: 6px 12px;
  border-radius: 999px;
  font-size: 12px;
  font-weight: 700;
  color: var(--brand-dark);
  background: rgba(31, 111, 235, 0.1);
  border: 1px solid rgba(31, 111, 235, 0.2);
}

.lead {
  color: var(--muted);
  line-height: 1.7;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 10px 16px;
  border-radius: 14px;
  border: 1px solid var(--line);
  background: #fff;
  font-weight: 700;
  box-shadow: 0 8px 16px rgba(20, 33, 61, 0.1);
  transition: transform 0.2s ease;
}

.btn:hover {
  transform: translateY(-1px);
}

.btn.primary {
  background: linear-gradient(135deg, var(--brand), #4aa3ff);
  color: #fff;
  border-color: transparent;
}

.btn.ghost {
  background: transparent;
}

.card {
  background: var(--card);
  border-radius: var(--radius);
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
  overflow: hidden;
}

.card-head {
  padding: 20px 20px 0;
}

.card-body {
  padding: 20px;
}

.form-grid {
  display: grid;
  gap: 14px;
}

.field {
  display: grid;
  gap: 6px;
}

.label {
  font-size: 12px;
  color: var(--muted);
}

.input {
  width: 100%;
  padding: 12px 14px;
  border-radius: 14px;
  border: 1px solid var(--line);
  background: #fff;
  font-size: 14px;
}

.msg {
  padding: 10px 12px;
  border-radius: 12px;
  font-size: 13px;
}

.msg.is-warn {
  background: rgba(255, 183, 3, 0.15);
  color: #9a5b02;
}

.feature-grid {
  display: grid;
  gap: 16px;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
}

.feature-card {
  background: #fff;
  border-radius: 16px;
  padding: 18px;
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
}

.video-list {
  display: grid;
  gap: 18px;
}

.video-card {
  display: grid;
  gap: 16px;
  grid-template-columns: 1fr 360px;
  border-radius: var(--radius);
  border: 1px solid var(--line);
  background: #fff;
  padding: 18px;
}

.video-player video {
  width: 100%;
  border-radius: 16px;
  background: #000;
}

.grid-two {
  display: grid;
  gap: 18px;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}

.table {
  width: 100%;
  border-collapse: collapse;
  font-size: 13px;
}

.table th,
.table td {
  padding: 8px 6px;
  border-bottom: 1px solid var(--line);
  text-align: left;
}

.thumb-preview {
  border-radius: 14px;
  overflow: hidden;
  border: 1px solid var(--line);
  margin-bottom: 12px;
}

.site-footer {
  border-top: 1px solid var(--line);
  padding: 20px 0;
  background: rgba(255, 255, 255, 0.9);
}

.footer-inner {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
  color: var(--muted);
  font-size: 12px;
}

@media (max-width: 900px) {
  .hero {
    grid-template-columns: 1fr;
  }

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

  .concept-copy {
    border-radius: var(--radius) var(--radius) 0 0;
    border-right: 1px solid var(--line);
    border-bottom: none;
  }

  .concept-media {
    border-radius: 0 0 var(--radius) var(--radius);
    border-left: 1px solid var(--line);
    border-top: none;
  }

  .notice-content {
    flex-direction: column;
  }

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