/* Dark UI base */
:root{
  --tree-line: rgba(255,255,255,.22);
  --tree-line-soft: rgba(255,255,255,.16);

  --tree-ink: #f3f3f3;
  --tree-muted: #bdf4e2;

  --tree-high-bg: rgba(255, 107, 107, .12);
  --tree-high-border: #ff6b6b;
  --tree-high-text: #ffb3b3;

  --tree-mid-bg: rgba(76, 141, 255, .12);
  --tree-mid-border: #4c8dff;
  --tree-mid-text: #c7ddff;

  --tree-low-bg: rgba(59, 178, 115, .12);
  --tree-low-border: #3bb273;
  --tree-low-text: #bdf4e2;

  --tree-low2-bg: rgba(169, 254, 228, .10);
  --tree-low2-border: #a9fee4;
  --tree-low2-text: #e8fff9;
}

/* ツリーの線部分 */
.tree ul {
  padding-left: 24px;
  position: relative;
  margin: 0;
}

.tree ul::before {
  content: "";
  border-left: 2px solid var(--tree-line-soft);
  position: absolute;
  top: 0;
  bottom: 0;
  left: 8px;
}

.tree li {
  list-style: none;
  margin: 8px 0;
  position: relative;
}

.tree li::before {
  content: "";
  border-top: 2px solid var(--tree-line-soft);
  position: absolute;
  top: 12px;
  left: -8px;
  width: 16px;
}

/* ノードの共通スタイル */
.tree span {
  display: inline-block;
  padding: 4px 8px;
  border-radius: 6px;
  font-size: 0.9rem;
  color: var(--tree-ink);
  background: rgba(10,10,10,.72);
  border: 1px solid rgba(255,255,255,.12);
  box-shadow: 0 10px 25px rgba(0,0,0,.45);
}

/* 階層ごとのベース */
.carrier {
  font-weight: 700;
}
.brand {
  font-weight: 600;
}
.mvno {
  font-weight: 500;
}
.mvno2nd {
  font-weight: 300;
}

/* 価格帯 × 品質の色分け（ダークUI版） */
.tier-high {
  width: 100%;
  background: var(--tree-high-bg);
  border: 1px solid var(--tree-high-border);
  color: var(--tree-high-text);
  padding: 4px;
}

.tier-mid {
  width: 80%;
  background: var(--tree-mid-bg);
  border: 1px solid var(--tree-mid-border);
  color: var(--tree-mid-text);
  padding: 4px;
}

.tier-low {
  width: 60%;
  background: var(--tree-low-bg);
  border: 1px solid var(--tree-low-border);
  color: var(--tree-low-text);
}

.tier-low2nd {
  width: 40%;
  background: var(--tree-low2-bg);
  border: 1px solid var(--tree-low2-border);
  color: var(--tree-low2-text);
  padding: 4px;
}

/* ちょっとだけ図解っぽく強調 */
.carrier.tier-high {
  box-shadow:
    0 0 0 2px rgba(255, 107, 107, 0.45),
    0 0 24px rgba(255, 107, 107, 0.35);
}
.brand.tier-mid {
  box-shadow:
    0 0 0 2px rgba(76, 141, 255, 0.40),
    0 0 22px rgba(76, 141, 255, 0.32);
}
.mvno.tier-low {
  box-shadow:
    0 0 0 1px rgba(59, 178, 115, 0.40),
    0 0 18px rgba(59, 178, 115, 0.30);
}
.mvno2nd.tier-low2nd {
  box-shadow:
    0 0 0 1px rgba(169, 254, 228, 0.40),
    0 0 16px rgba(169, 254, 228, 0.28);
}