/* index.html 専用：シンプルな装飾・読みやすさ優先 */

:root {
  --index-text: #2c2c2c;
  --index-text-muted: #444;
  --index-border: rgba(0, 0, 0, 0.08);
  --index-border-soft: rgba(0, 0, 0, 0.06);
  --index-shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.04), 0 8px 20px rgba(0, 0, 0, 0.05);
  --index-shadow-card: 0 1px 3px rgba(0, 0, 0, 0.05), 0 12px 32px rgba(0, 0, 0, 0.04);
  --index-radius: 14px;
  --index-radius-hero: 18px 4px 18px 4px;
  --index-line: rgba(33, 118, 255, 0.14);
}

/* --- Hero 周り --- */
.index-mv {
  padding-top: clamp(1.25rem, 4vw, 2rem);
  padding-bottom: clamp(1.25rem, 3.5vw, 2rem);
  background: linear-gradient(180deg, rgba(76, 198, 237, 0.06) 0%, rgba(255, 255, 255, 0) 72%);
}

.index-hook {
  padding-top: clamp(1rem, 3vw, 1.5rem);
  padding-bottom: clamp(0.75rem, 2.5vw, 1.25rem);
}

.index-hook__card {
  position: relative;
  overflow: hidden;
  background: #fff;
  border: 1px solid var(--index-border-soft);
  border-radius: var(--index-radius);
  box-shadow: var(--index-shadow-sm);
  padding: clamp(1rem, 3vw, 1.5rem);
}

.index-hero-card .index-hook__card {
  margin-top: clamp(1.2rem, 3.2vw, 1.6rem);
}

.index-hook__title {
  margin: 0;
  font-size: clamp(1.05rem, 0.95rem + 0.45vw, 1.25rem);
  letter-spacing: 0.06em;
  color: #222;
}

.index-hook__video-wrap {
  margin-top: 0.85rem;
  border-radius: 12px;
  overflow: hidden;
  background: #000;
}

.index-hook__video {
  display: block;
  width: 100%;
  height: auto;
  aspect-ratio: 16 / 9;
  object-fit: cover;
}

.index-hook__controls {
  margin-top: 0.85rem;
  display: grid;
  gap: 0.6rem;
}

.index-hook__controls-row {
  display: grid;
  gap: 0.5rem;
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.index-hook__controls-row:last-child {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.index-hook__btn {
  border: 1px solid var(--index-border);
  background: #fff;
  color: #333;
  border-radius: 10px;
  padding: 0.65rem 0.75rem;
  font-size: 0.92rem;
  font-weight: 700;
  line-height: 1.2;
  cursor: pointer;
  transition: background-color 0.15s ease, color 0.15s ease, border-color 0.15s ease;
}

.index-hook__btn:hover {
  background: #f7f8f9;
}

.index-hook__btn.is-active {
  background: var(--main-color);
  border-color: var(--main-color);
  color: #fff;
}

.index-hook__btn:focus-visible {
  outline: 2px solid var(--main-color);
  outline-offset: 2px;
}

.index-hero-card {
  position: relative;
  overflow: hidden;
  max-width: 760px;
  margin: 0 auto;
  padding: clamp(1.9rem, 5.2vw, 3rem) clamp(1.4rem, 4vw, 2.15rem);
  padding-left: clamp(1.5rem, 4.5vw, 2.1rem);
  background: var(--base-color);
  border-radius: var(--index-radius-hero);
  border: 1px solid var(--index-border-soft);
  box-shadow: var(--index-shadow-card);
}

.index-hero-card::before {
  content: "";
  position: absolute;
  left: 0;
  top: 1rem;
  bottom: 1rem;
  width: 4px;
  border-radius: 999px;
  background: linear-gradient(180deg, var(--main-color), var(--accent-color));
  opacity: 0.8;
}

.index-kicker {
  display: inline-block;
  margin: 0 0 0.85rem;
  padding: 0.38rem 0.88rem;
  background: var(--main-color);
  color: var(--text-sub-color);
  font-size: 0.8125rem;
  font-weight: 700;
  border-radius: 999px;
  letter-spacing: 0.04em;
}

.index-hero-title {
  margin: 0;
  max-width: 22em;
  font-size: clamp(1.42rem, 1.08rem + 1.35vw, 2.05rem);
  font-weight: 800;
  line-height: 1.52;
  color: var(--text-main-color);
  letter-spacing: 0.03em;
}

/* 本文 */
.index-body {
  margin: 0;
  max-width: 40rem;
  font-size: clamp(1rem, 0.95rem + 0.22vw, 1.0625rem);
  font-weight: 500;
  line-height: 1.92;
  color: var(--index-text);
}

.index-body + .index-body,
.index-h2 + .index-body,
.index-body + .index-checklist,
.index-checklist + .index-body {
  margin-top: clamp(1rem, 3vw, 1.35rem);
}

.index-body--lead {
  margin-top: clamp(1.2rem, 3.4vw, 1.7rem);
}

.index-highlight-row {
  margin-top: clamp(1.4rem, 3.8vw, 1.9rem);
  display: grid;
  gap: 0.75rem;
}

.index-highlight-item {
  padding: 0.95rem 1rem 0.95rem 1.05rem;
  background: #fff;
  border-radius: 10px;
  border: 1px solid var(--index-border-soft);
  border-left: 4px solid var(--main-color);
  box-shadow: var(--index-shadow-sm);
  font-weight: 700;
  font-size: clamp(0.94rem, 0.89rem + 0.18vw, 1rem);
  line-height: 1.62;
  color: var(--index-text-muted);
}

.index-highlight-item--accent {
  border-left-color: var(--accent-color);
}

.index-hero-cta {
  margin-top: clamp(1.5rem, 4vw, 2rem);
}

.index-btn-primary {
  display: block;
  width: min(100%, 520px);
  margin: 0 auto;
  text-align: center;
  background: var(--accent-color);
  color: var(--text-sub-color);
  padding: 0.95rem 1.25rem;
  border-radius: 999px;
  font-weight: 800;
  font-size: 1.03rem;
  line-height: 1.45;
  box-shadow: 0 4px 14px rgba(239, 35, 60, 0.28);
  text-decoration: none;
  transition: opacity 0.2s ease, transform 0.15s ease;
}

.index-btn-primary:hover {
  opacity: 0.94;
}

.index-btn-primary:focus-visible {
  outline: 2px solid var(--main-color);
  outline-offset: 3px;
}

/* メイン縦ストリーム */
.index-stack {
  position: relative;
  z-index: 15;
  display: flex;
  flex-direction: column;
  gap: clamp(2.6rem, 6vw, 4.25rem);
  padding-bottom: 2.5rem;
}

.index-block {
  position: relative;
  overflow: hidden;
  width: 100%;
  padding: clamp(1.95rem, 4.8vw, 2.85rem) clamp(1.35rem, 4.2vw, 2.15rem);
  background: #f7f8f9;
  border-radius: var(--index-radius);
  border: 1px solid var(--index-border-soft);
  box-shadow: var(--index-shadow-sm);
}

.index-block > .index-h2,
.index-block > .index-body,
.index-block > .index-checklist,
.index-block > .index-flow,
.index-block > .index-mini-list {
  max-width: 44rem;
}

.index-h2 {
  margin: 0;
  padding-bottom: 0.55rem;
  margin-bottom: 0.15rem;
  border-bottom: 2px solid var(--index-line);
  font-size: clamp(1.22rem, 1rem + 1vw, 1.72rem);
  font-weight: 800;
  line-height: 1.5;
  color: var(--text-main-color);
  letter-spacing: 0.02em;
}

.index-checklist {
  margin: clamp(0.95rem, 2.8vw, 1.2rem) 0 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 0.55rem;
}

.index-checklist li {
  padding: 0.8rem 0.9rem 0.8rem 1rem;
  background: #fff;
  border-radius: 10px;
  border: 1px solid var(--index-border-soft);
  border-left: 4px solid var(--main-color);
  font-size: clamp(0.96rem, 0.92rem + 0.15vw, 1.03rem);
  line-height: 1.62;
  color: var(--index-text);
}

/* 学習の流れ */
.index-flow {
  margin-top: clamp(1.1rem, 3.2vw, 1.5rem);
  display: grid;
  gap: 0.35rem;
}

.index-flow__step {
  background: #fff;
  border: 1px solid var(--index-border);
  border-radius: 12px;
  padding: 0.88rem 1rem;
  text-align: center;
  font-weight: 700;
  font-size: clamp(0.96rem, 0.91rem + 0.15vw, 1.03rem);
  color: var(--index-text);
  letter-spacing: 0.02em;
}

.index-flow__arrow {
  text-align: center;
  color: #9a9a9a;
  font-weight: 600;
  font-size: 0.95rem;
  line-height: 1.3;
  padding: 0.1rem 0;
  user-select: none;
}

/* 帯 */
.index-band {
  position: relative;
  overflow: hidden;
  border-radius: var(--index-radius);
  padding: clamp(1.75rem, 4.8vw, 2.4rem) clamp(1.25rem, 4vw, 2rem);
  text-align: center;
  box-shadow: var(--index-shadow-sm);
}

/* 各セクション左側のグラデーション縦ライン */
.index-hook__card::after,
.index-block::after,
.index-band::after {
  content: "";
  position: absolute;
  left: 0;
  top: 1rem;
  bottom: 1rem;
  width: 4px;
  border-radius: 999px;
  background: linear-gradient(180deg, var(--main-color) 0%, #8a5cff 45%, var(--accent-color) 100%);
  opacity: 0.8;
  pointer-events: none;
}

.index-band--main {
  background: var(--main-color);
  color: var(--text-sub-color);
}

.index-band--accent {
  background: var(--accent-color);
  color: var(--text-sub-color);
}

.index-band__title {
  margin: 0 auto;
  max-width: 22em;
  font-size: clamp(1.18rem, 1rem + 0.95vw, 1.72rem);
  line-height: 1.58;
  font-weight: 800;
  letter-spacing: 0.02em;
}

.index-band__text {
  margin: clamp(0.95rem, 2.8vw, 1.2rem) auto 0;
  max-width: 36em;
  line-height: 1.92;
  font-size: clamp(0.96rem, 0.92rem + 0.15vw, 1.04rem);
  font-weight: 500;
  opacity: 0.97;
}

.index-band__text strong {
  font-weight: 800;
  opacity: 1;
}

.index-band__actions {
  margin-top: clamp(1.4rem, 3.6vw, 1.8rem);
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  align-items: center;
}

.index-btn-on-accent {
  display: block;
  width: min(100%, 520px);
  text-align: center;
  background: var(--main-color);
  color: var(--text-sub-color);
  padding: 0.95rem 1.25rem;
  border-radius: 999px;
  font-weight: 800;
  font-size: 1.03rem;
  text-decoration: none;
  box-shadow: 0 4px 14px rgba(0, 0, 0, 0.15);
  transition: opacity 0.2s ease;
}

.index-btn-on-accent:hover {
  opacity: 0.94;
}

.index-btn-on-accent:focus-visible {
  outline: 2px solid #fff;
  outline-offset: 3px;
}

.index-link-subtle {
  display: inline-block;
  color: var(--text-sub-color);
  font-weight: 700;
  text-decoration: underline;
  text-underline-offset: 4px;
  text-decoration-thickness: 1px;
}

.index-link-subtle:focus-visible {
  outline: 2px solid #fff;
  outline-offset: 3px;
  border-radius: 2px;
}

.index-mini-list {
  margin-top: clamp(0.95rem, 2.8vw, 1.2rem);
  display: grid;
  gap: 0.55rem;
}

.index-mini-list > div {
  padding: 0.8rem 1rem;
  background: #fff;
  border-radius: 10px;
  border: 1px solid var(--index-border-soft);
  border-left: 4px solid var(--main-color);
  line-height: 1.62;
  color: var(--index-text);
  font-size: clamp(0.96rem, 0.92rem + 0.15vw, 1.03rem);
}

/* common.css の br 非表示指定をLP領域で打ち消す */
.index-mv br,
.index-stack br {
  display: inline;
}

@media (max-width: 767px) {
  .index-hero-card::before {
    top: 1rem;
    bottom: 1rem;
  }

  .index-body {
    line-height: 2;
  }

  .index-mv br,
  .index-stack br {
    display: inline;
  }

  .index-h2 {
    font-size: clamp(1.14rem, 1rem + 0.5vw, 1.5rem);
  }

  .index-hook__btn {
    font-size: 0.88rem;
    padding: 0.62rem 0.55rem;
  }
}