/* オペラボとはセクション：サイト全体の黒×金×赤デザインに統一し、理念を目立たせる */
#about.section-alt {
  background: var(--bg-base) !important;
  background: linear-gradient(180deg, #000000 0%, #0a0a0a 50%, #000000 100%) !important;
  backdrop-filter: none;
  color: var(--text-base);
}

/* 理念ブロック：フル幅・枠なし（白背景にならないよう明示） */
#about .philosophy-accordion-section {
  background-color: #000000;
  background: radial-gradient(140% 200% at 50% 0%, #1a0a0a 0%, #0d0505 25%, #0a0a0a 50%, #000000 100%);
  color: var(--text-base);
  margin: 2.5rem calc(-50vw + 50%);
  padding: clamp(3rem, 7vw, 5rem) clamp(0.75rem, 4vw, 1.5rem);
  width: 100vw;
  box-sizing: border-box;
  position: relative;
}

#about .philosophy-accordion-container {
  width: min(100%, 720px);
  margin: 0 auto;
  padding: 1.75rem 1rem;
  position: relative;
  overflow: hidden;
}

#about .philosophy-accordion {
  display: flex;
  flex-direction: column;
  gap: 0;
  list-style: none;
  margin: 0;
  padding: 0;
  background: transparent;
}

/* 区切り線：サイト全体のダークテーマに合わせる（閉じたときに説明文が隙間から見えないよう overflow でクリップ） */
#about .philosophy-accordion-item {
  border-bottom: 1px solid var(--border-soft);
  background: transparent;
  overflow: hidden;
}

#about .philosophy-accordion-item:first-child {
  border-top: none;
}

#about .philosophy-accordion-head {
  display: flex;
  align-items: center;
  gap: 1rem;
  width: 100%;
  padding: 1.1rem 0;
  background-color: transparent;
  background: transparent;
  border: none;
  cursor: pointer;
  text-align: left;
  font: inherit;
  color: var(--text-base);
  -webkit-tap-highlight-color: rgba(212, 175, 55, 0.18);
  transition:
    background-color 0.2s ease,
    color 0.2s ease,
    border-color 0.2s ease;
  border-bottom: 1px solid var(--border-soft);
}

#about .philosophy-accordion-head:hover,
#about .philosophy-accordion-head:focus-visible {
  background-color: rgba(212, 175, 55, 0.08);
  outline: none;
}

#about .philosophy-accordion-head:hover .philosophy-accordion-title,
#about .philosophy-accordion-head:focus-visible .philosophy-accordion-title {
  color: var(--accent-gold-bright);
}

#about .philosophy-accordion-item.is-open .philosophy-accordion-head {
  color: var(--text-base);
  background: linear-gradient(135deg, var(--accent-gold-soft), transparent 60%);
  border-bottom-color: var(--border-gold);
}

#about .philosophy-accordion-item.is-open .philosophy-accordion-title {
  color: var(--accent-gold);
  font-weight: 600;
}

/* 頭文字（オ・ペ・ラ・ボ）：丸形・クラシックな配色（枠・白い光なし） */
#about .philosophy-accordion-char {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 4.5rem;
  height: 4.5rem;
  flex-shrink: 0;
  font-size: 2.5rem;
  font-weight: 700;
  color: #ffffff;
  border-radius: 50%;
}

#about .philosophy-accordion-item:nth-child(1) .philosophy-accordion-char {
  background: radial-gradient(circle at 30% 20%, #e63939 0%, #b01515 35%, #8B0000 65%, #3d0000 100%);
}

#about .philosophy-accordion-item:nth-child(2) .philosophy-accordion-char {
  background: radial-gradient(circle at 30% 20%, #f4d03f 0%, #d4af37 40%, #b8960f 75%, #6b5a0a 100%);
}

#about .philosophy-accordion-item:nth-child(3) .philosophy-accordion-char {
  background: radial-gradient(circle at 30% 20%, #e8e8e8 0%, #9a9a9a 35%, #4a4a4a 70%, #1a1a1a 100%);
}

#about .philosophy-accordion-item:nth-child(4) .philosophy-accordion-char {
  background: radial-gradient(circle at 30% 20%, #2a2a2a 0%, #1a1a1a 50%, #0a0a0a 100%);
}

#about .philosophy-accordion-title {
  flex: 1;
  font-size: clamp(1rem, 2.2vw, 1.125rem);
  line-height: 1.45;
  letter-spacing: 0.03em;
  color: var(--text-base);
  text-shadow: 0 1px 4px rgba(0, 0, 0, 0.6);
}

#about .philosophy-accordion-icon {
  flex-shrink: 0;
  width: 1.25rem;
  height: 1.25rem;
  position: relative;
  color: rgba(255, 255, 255, 0.6);
  transition: transform 0.35s cubic-bezier(0.4, 0, 0.2, 1), color 0.2s ease;
}

#about .philosophy-accordion-item.is-open .philosophy-accordion-icon {
  color: var(--accent-gold);
  transform: rotate(-180deg);
}

.philosophy-accordion-icon::before {
  content: '';
  position: absolute;
  left: 50%;
  top: 50%;
  width: 6px;
  height: 6px;
  margin-left: -4px;
  margin-top: -5px;
  border-right: 2px solid currentColor;
  border-bottom: 2px solid currentColor;
  transform: rotate(45deg);
}

#about .philosophy-accordion-body {
  display: grid;
  grid-template-rows: 0fr;
  transition: grid-template-rows 0.35s cubic-bezier(0.4, 0, 0.2, 1);
  overflow: hidden;
  background: #0a0a0a;
  min-height: 0;
}

#about .philosophy-accordion-item.is-open .philosophy-accordion-body {
  grid-template-rows: 1fr;
}

#about .philosophy-accordion-body-inner {
  min-height: 0;
  overflow: hidden;
  background: #0a0a0a;
  color: var(--text-muted);
  padding: 0 0 1rem 0;
}

#about .philosophy-accordion-body-inner p {
  margin: 0;
  padding: 1rem 0 0;
  padding-left: calc(4.5rem + 1rem);
  padding-right: 0.25rem;
  font-size: clamp(0.9375rem, 2.2vw, 1.0625rem);
  line-height: 1.8;
  letter-spacing: 0.02em;
  color: var(--text-soft);
}

.philosophy-accordion-body-inner p:last-child {
  padding-bottom: 0;
}

@media (min-width: 600px) {
  #about .philosophy-accordion-section {
    padding: clamp(3rem, 6.5vw, 4.5rem) 2rem;
  }

  #about .philosophy-accordion-head {
    padding: 1.25rem 0;
  }

  #about .philosophy-accordion-char {
    width: 5rem;
    height: 5rem;
    font-size: 2.75rem;
  }

  #about .philosophy-accordion-body-inner p {
    padding-left: calc(5rem + 1rem);
  }
}