/* ================================================
   BrookyU — Learning Content Styles
   Extends BrookyMonster base (../css/styles.css)
   ================================================ */

/* ── BrookyU header badge ── */
.bu-tag {
  font-size: 0.58rem;
  font-weight: 700;
  letter-spacing: 0.3em;
  text-transform: uppercase;
  color: var(--red);
  border: 1px solid var(--red);
  padding: 0.2rem 0.6rem;
  margin-left: 0.75rem;
  flex-shrink: 0;
}

.bu-back {
  margin-left: auto;
  font-size: 0.72rem;
  font-weight: 500;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--gray);
  transition: color 0.15s;
  flex-shrink: 0;
}

.bu-back:hover { color: var(--red); }

/* ── Breadcrumb ── */
.bu-breadcrumb {
  background: var(--offwhite);
  border-bottom: 1px solid var(--lgray);
  padding: 0.65rem 2rem;
}

.bu-breadcrumb__inner {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.63rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--gray);
  flex-wrap: wrap;
}

.bu-breadcrumb__inner a { color: var(--gray); transition: color 0.15s; }
.bu-breadcrumb__inner a:hover { color: var(--red); }
.bu-breadcrumb__sep { color: var(--lgray); }
.bu-breadcrumb__current { color: var(--black); font-weight: 600; }

/* ── Page Hero ── */
.bu-hero {
  padding: 4rem 2rem 3rem;
  border-bottom: 1px solid var(--lgray);
}

.bu-hero__inner {
  max-width: 1200px;
  margin: 0 auto;
}

.bu-hero__eyebrow {
  font-size: 0.63rem;
  font-weight: 700;
  letter-spacing: 0.3em;
  text-transform: uppercase;
  color: var(--red);
  margin-bottom: 1rem;
}

.bu-hero__title {
  font-size: clamp(1.8rem, 4vw, 3rem);
  font-weight: 300;
  letter-spacing: -0.01em;
  color: var(--black);
  margin-bottom: 1rem;
  line-height: 1.1;
}

.bu-hero__title strong { font-weight: 600; }

.bu-hero__desc {
  font-size: 0.95rem;
  color: var(--gray);
  max-width: 640px;
  line-height: 1.75;
}

/* ── Content wrapper ── */
.bu-section {
  padding: 3.5rem 2rem;
}

.bu-section--gray { background: var(--offwhite); }

.bu-inner {
  max-width: 1200px;
  margin: 0 auto;
}

/* ── Info boxes ── */
.bu-box-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
  margin-bottom: 1.5rem;
}

.bu-box {
  border: 1px solid var(--lgray);
  padding: 1.75rem;
  background: var(--white);
}

.bu-box__label {
  font-size: 0.6rem;
  font-weight: 700;
  letter-spacing: 0.28em;
  text-transform: uppercase;
  color: var(--red);
  margin-bottom: 1rem;
}

.bu-box__list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.bu-box__list li {
  font-size: 0.83rem;
  color: var(--black);
  padding: 0.45rem 0;
  border-bottom: 1px solid var(--lgray);
  display: flex;
  align-items: flex-start;
  gap: 0.6rem;
  line-height: 1.55;
}

.bu-box__list li:last-child { border-bottom: none; }

.bu-box__list li::before {
  content: '—';
  color: var(--red);
  flex-shrink: 0;
  font-weight: 600;
}

.bu-spec-callout {
  background: var(--offwhite);
  border: 1px solid var(--lgray);
  border-left: 3px solid var(--red);
  padding: 1rem 1.5rem;
  font-size: 0.82rem;
  color: var(--black);
  line-height: 1.6;
}

/* ── Oil Family Cards ── */
.bu-oil-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
}

.bu-oil-card {
  border: 1px solid var(--lgray);
  background: var(--white);
  overflow: hidden;
}

.bu-oil-card__hd {
  padding: 1.25rem 1.5rem 1rem;
  border-bottom: 1px solid var(--lgray);
}

.bu-oil-card__type {
  font-size: 0.58rem;
  font-weight: 700;
  letter-spacing: 0.3em;
  text-transform: uppercase;
  color: var(--red);
  margin-bottom: 0.35rem;
}

.bu-oil-card__name {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--black);
  margin-bottom: 0.2rem;
}

.bu-oil-card__range {
  font-size: 0.75rem;
  color: var(--gray);
}

/* Viscosity scale */
.bu-visc {
  padding: 1rem 1.5rem;
  border-bottom: 1px solid var(--lgray);
  background: var(--offwhite);
}

.bu-visc__meta {
  display: flex;
  justify-content: space-between;
  font-size: 0.58rem;
  font-weight: 600;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--gray);
  margin-bottom: 0.45rem;
}

.bu-visc__track {
  height: 5px;
  background: var(--lgray);
  position: relative;
}

.bu-visc__fill {
  position: absolute;
  top: 0;
  height: 100%;
  background: var(--red);
  opacity: 0.8;
}

/* Card body */
.bu-oil-card__body {
  padding: 1.25rem 1.5rem;
}

.bu-sub-label {
  font-size: 0.58rem;
  font-weight: 700;
  letter-spacing: 0.25em;
  text-transform: uppercase;
  color: var(--gray);
  margin-bottom: 0.5rem;
  margin-top: 1rem;
}

.bu-sub-label:first-child { margin-top: 0; }

.bu-dot-list {
  list-style: none;
  padding: 0;
  margin: 0 0 1rem;
}

.bu-dot-list li {
  font-size: 0.82rem;
  color: var(--black);
  padding: 0.28rem 0 0.28rem 1rem;
  position: relative;
  line-height: 1.5;
}

.bu-dot-list li::before {
  content: '';
  position: absolute;
  left: 0;
  top: 0.62rem;
  width: 4px;
  height: 4px;
  background: var(--red);
  border-radius: 50%;
}

/* Product examples inside cards */
.bu-products {
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}

.bu-product {
  border: 1px solid var(--lgray);
  padding: 0.85rem 1rem;
  background: var(--offwhite);
}

.bu-product__name {
  font-size: 0.73rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  color: var(--black);
  margin-bottom: 0.35rem;
}

.bu-product__specs {
  display: flex;
  gap: 1.25rem;
  flex-wrap: wrap;
}

.bu-product__spec {
  font-size: 0.67rem;
  color: var(--gray);
}

.bu-product__spec strong {
  color: var(--black);
  font-weight: 600;
}

/* ── Properties cards ── */
.bu-prop-grid {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 1.5rem;
}

.bu-prop-card {
  border: 1px solid var(--lgray);
  padding: 1.5rem;
  background: var(--white);
}

.bu-prop-card__num {
  font-size: 0.58rem;
  font-weight: 700;
  letter-spacing: 0.28em;
  text-transform: uppercase;
  color: var(--red);
  margin-bottom: 0.4rem;
}

.bu-prop-card__title {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--black);
  margin-bottom: 0.75rem;
}

.bu-prop-card__desc {
  font-size: 0.8rem;
  color: var(--gray);
  line-height: 1.7;
  margin-bottom: 1rem;
}

.bu-mini-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.75rem;
}

.bu-mini-table th {
  font-size: 0.58rem;
  font-weight: 700;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--gray);
  padding: 0.4rem 0.5rem 0.4rem 0;
  border-bottom: 1px solid var(--lgray);
  text-align: left;
}

.bu-mini-table td {
  padding: 0.4rem 0.5rem 0.4rem 0;
  border-bottom: 1px solid var(--lgray);
  color: var(--black);
}

.bu-mini-table tr:last-child td { border-bottom: none; }
.bu-mini-table td:first-child { font-weight: 500; }

/* ── Lane behavior comparison ── */
.bu-compare-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
  margin-bottom: 2rem;
}

.bu-compare-card {
  border: 1px solid var(--lgray);
  overflow: hidden;
}

.bu-compare-card__hd {
  padding: 0.8rem 1.25rem;
  background: var(--black);
  color: var(--white);
  font-size: 0.62rem;
  font-weight: 700;
  letter-spacing: 0.25em;
  text-transform: uppercase;
}

.bu-compare-card__body { padding: 1.25rem; }

.bu-compare-card__body ul { list-style: none; padding: 0; }

.bu-compare-card__body li {
  font-size: 0.82rem;
  color: var(--black);
  padding: 0.4rem 0;
  border-bottom: 1px solid var(--lgray);
  line-height: 1.5;
}

.bu-compare-card__body li:last-child { border-bottom: none; }

/* ── Insight callouts ── */
.bu-insight {
  border-left: 3px solid var(--red);
  background: var(--offwhite);
  padding: 1.25rem 1.5rem;
  margin-bottom: 1rem;
}

.bu-insight__label {
  font-size: 0.58rem;
  font-weight: 700;
  letter-spacing: 0.28em;
  text-transform: uppercase;
  color: var(--red);
  margin-bottom: 0.45rem;
}

.bu-insight__text {
  font-size: 0.85rem;
  color: var(--black);
  line-height: 1.7;
}

.bu-insight__text strong { font-weight: 600; }

/* ── Variables impact table ── */
.bu-vars-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.8rem;
}

.bu-vars-table thead tr { border-bottom: 2px solid var(--black); }

.bu-vars-table th {
  font-size: 0.6rem;
  font-weight: 700;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--black);
  padding: 0.75rem 1rem;
  text-align: left;
  background: var(--offwhite);
}

.bu-vars-table td {
  padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--lgray);
  color: var(--black);
  vertical-align: top;
}

.bu-vars-table td:first-child {
  font-weight: 600;
  white-space: nowrap;
}

.bu-vars-table tr:last-child td { border-bottom: none; }
.bu-vars-table tr:hover td { background: var(--offwhite); }

/* ================================================
   HUB PAGE — Course index
   ================================================ */

/* ── Hub hero ── */
.bu-hub-hero {
  padding: 4.5rem 2rem 3.5rem;
  border-bottom: 1px solid var(--lgray);
}

.bu-hub-hero__inner {
  max-width: 1200px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 3rem;
  align-items: end;
}

.bu-hub-hero__eyebrow {
  font-size: 0.63rem;
  font-weight: 700;
  letter-spacing: 0.3em;
  text-transform: uppercase;
  color: var(--red);
  margin-bottom: 1rem;
}

.bu-hub-hero__title {
  font-size: clamp(2rem, 5vw, 3.5rem);
  font-weight: 300;
  color: var(--black);
  line-height: 1.05;
  letter-spacing: -0.02em;
  margin-bottom: 1.25rem;
}

.bu-hub-hero__title strong { font-weight: 600; }

.bu-hub-hero__desc {
  font-size: 0.9rem;
  color: var(--gray);
  max-width: 560px;
  line-height: 1.8;
}

.bu-hub-hero__stat { text-align: right; }

.bu-hub-hero__stat-num {
  font-size: 3.5rem;
  font-weight: 300;
  color: var(--black);
  line-height: 1;
  margin-bottom: 0.3rem;
  letter-spacing: -0.03em;
}

.bu-hub-hero__stat-label {
  font-size: 0.58rem;
  font-weight: 700;
  letter-spacing: 0.28em;
  text-transform: uppercase;
  color: var(--gray);
}

/* ── Course grid ── */
.bu-course-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
  margin-top: 1.5rem;
}

/* ── Course card ── */
.bu-course-card {
  border: 1px solid var(--lgray);
  background: var(--white);
  display: flex;
  flex-direction: column;
  color: inherit;
  transition: box-shadow 0.2s, border-color 0.2s;
}

.bu-course-card:hover {
  box-shadow: 0 6px 24px rgba(0,0,0,0.09);
  border-color: #ccc;
}

/* Thumbnail */
.bu-course-card__thumb {
  aspect-ratio: 16 / 9;
  background: var(--black);
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  padding: 1.25rem 1.5rem;
  position: relative;
  overflow: hidden;
}

/* Large watermark number */
.bu-course-card__num {
  position: absolute;
  top: 0.5rem;
  right: 1rem;
  font-size: 5rem;
  font-weight: 700;
  color: rgba(255,255,255,0.05);
  line-height: 1;
  letter-spacing: -0.04em;
  user-select: none;
  z-index: 0;
}

.bu-course-card__thumb-cat {
  font-size: 0.55rem;
  font-weight: 700;
  letter-spacing: 0.28em;
  text-transform: uppercase;
  color: var(--red);
  margin-bottom: 0.35rem;
  position: relative;
  z-index: 1;
}

.bu-course-card__thumb-title {
  font-size: 1.15rem;
  font-weight: 600;
  color: var(--white);
  line-height: 1.2;
  position: relative;
  z-index: 1;
}

/* Per-course thumbnail treatments */
.bu-course-card__thumb--oils {
  background: linear-gradient(155deg, #1c1008 0%, #111111 65%);
}

.bu-course-card__thumb--oils::before {
  content: '';
  position: absolute;
  inset: 0;
  background: radial-gradient(circle at 85% 15%, rgba(204,17,17,0.18), transparent 55%);
}

.bu-course-card__thumb--surfaces::before {
  content: '';
  position: absolute;
  inset: 0;
  background: repeating-linear-gradient(
    90deg,
    transparent 0px, transparent 17px,
    rgba(255,255,255,0.045) 17px, rgba(255,255,255,0.045) 18px
  );
}

.bu-course-card__thumb--soon { background: #555; }

.bu-course-card__thumb--layout {
  background: linear-gradient(155deg, #0d0818 0%, #111111 65%);
}

.bu-course-card__thumb--layout::before {
  content: '';
  position: absolute;
  inset: 0;
  background:
    radial-gradient(circle at 28% 65%, rgba(204,17,17,0.22), transparent 45%),
    radial-gradient(circle at 72% 30%, rgba(255,255,255,0.04), transparent 38%);
}

/* Card body */
.bu-course-card__body {
  padding: 1.25rem 1.5rem 1.5rem;
  display: flex;
  flex-direction: column;
  flex: 1;
}

.bu-course-card__desc {
  font-size: 0.82rem;
  color: var(--gray);
  line-height: 1.75;
  margin-bottom: 1.25rem;
  flex: 1;
}

.bu-course-card__divider {
  height: 1px;
  background: var(--lgray);
  margin-bottom: 1rem;
}

.bu-course-card__meta {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
  margin-bottom: 1.25rem;
}

.bu-course-card__metaitem {
  font-size: 0.62rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--gray);
}

.bu-course-card__cta {
  display: inline-flex;
  align-items: center;
  font-size: 0.68rem;
  font-weight: 600;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--black);
  border: 1px solid var(--black);
  padding: 0.6rem 1.1rem;
  transition: background 0.15s, color 0.15s;
  align-self: flex-start;
}

.bu-course-card:hover .bu-course-card__cta {
  background: var(--black);
  color: var(--white);
}

/* Coming soon state */
.bu-course-card--soon {
  opacity: 0.45;
  pointer-events: none;
}

.bu-course-card__soon-badge {
  position: absolute;
  top: 0.9rem;
  right: 0.9rem;
  font-size: 0.52rem;
  font-weight: 700;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  background: var(--white);
  color: var(--black);
  padding: 0.22rem 0.55rem;
  z-index: 2;
}

/* ── Hub responsive ── */
@media (max-width: 900px) {
  .bu-hub-hero__inner { grid-template-columns: 1fr; gap: 1.5rem; }
  .bu-hub-hero__stat { text-align: left; }
  .bu-course-grid { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 600px) {
  .bu-hub-hero { padding: 2.5rem 1.25rem 2rem; }
  .bu-course-grid { grid-template-columns: 1fr; }
}

/* ================================================
   COURSE PAGE COMPONENTS (existing)
   ================================================ */

/* ================================================
   COMPLETE SYSTEM PAGE — New Components
   ================================================ */

/* ── Three-variable cards ── */
.bu-var-grid {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 1.5rem;
  margin-bottom: 2rem;
}

.bu-var-card { border: 1px solid var(--lgray); overflow: hidden; }

.bu-var-card__top {
  background: var(--black);
  padding: 1.4rem 1.5rem;
}

.bu-var-card__label {
  font-size: 0.55rem;
  font-weight: 700;
  letter-spacing: 0.3em;
  text-transform: uppercase;
  color: var(--red);
  margin-bottom: 0.35rem;
}

.bu-var-card__title {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--white);
  margin-bottom: 0.2rem;
}

.bu-var-card__meta {
  font-size: 0.72rem;
  color: rgba(255,255,255,0.38);
  font-style: italic;
}

.bu-var-card__body { padding: 1.25rem 1.5rem; }

/* ── Interaction section (A / B / C) ── */
.bu-interact-label {
  font-size: 0.62rem;
  font-weight: 700;
  letter-spacing: 0.28em;
  text-transform: uppercase;
  color: var(--red);
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--lgray);
  margin-bottom: 1.5rem;
}

.bu-interact-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
  margin-bottom: 2.5rem;
}

.bu-interact-card { border: 1px solid var(--lgray); overflow: hidden; }

.bu-interact-card__hd {
  background: var(--offwhite);
  border-bottom: 1px solid var(--lgray);
  padding: 0.8rem 1.25rem;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--black);
}

.bu-interact-card__body { padding: 1.25rem; }

/* Cause → Effect table inside interaction card */
.bu-cause-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.75rem;
  margin-bottom: 1rem;
}

.bu-cause-table th {
  font-size: 0.56rem;
  font-weight: 700;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--gray);
  padding: 0.35rem 0.5rem 0.35rem 0;
  border-bottom: 1px solid var(--lgray);
  text-align: left;
}

.bu-cause-table td {
  padding: 0.4rem 0.5rem 0.4rem 0;
  border-bottom: 1px solid var(--lgray);
  color: var(--black);
  vertical-align: top;
  line-height: 1.45;
}

.bu-cause-table tr:last-child td { border-bottom: none; }
.bu-cause-table td:first-child { color: var(--gray); }

/* "What bowlers feel" quote */
.bu-quote {
  border-left: 2px solid var(--lgray);
  padding: 0.6rem 1rem;
  margin-top: 0.75rem;
  font-size: 0.8rem;
  font-style: italic;
  color: var(--gray);
  line-height: 1.6;
  background: var(--offwhite);
}

/* ── Scenario cards ── */
.bu-scenario-grid {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 1.5rem;
}

.bu-scenario-card { border: 1px solid var(--lgray); overflow: hidden; }

.bu-scenario-card__hd {
  background: var(--black);
  padding: 1.25rem 1.5rem;
}

.bu-scenario-card__num {
  font-size: 0.55rem;
  font-weight: 700;
  letter-spacing: 0.28em;
  text-transform: uppercase;
  color: var(--red);
  margin-bottom: 0.35rem;
}

.bu-scenario-card__eq {
  font-size: 0.7rem;
  color: rgba(255,255,255,0.5);
  margin-bottom: 0.5rem;
  line-height: 1.55;
  font-weight: 400;
}

.bu-scenario-card__title {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--white);
}

.bu-scenario-card__body { padding: 1.25rem 1.5rem; }

/* Chain reaction numbered list */
.bu-chain {
  list-style: none;
  padding: 0;
  margin: 0 0 1rem;
  counter-reset: chain-counter;
}

.bu-chain li {
  font-size: 0.8rem;
  color: var(--black);
  padding: 0.4rem 0 0.4rem 1.4rem;
  position: relative;
  border-bottom: 1px solid var(--lgray);
  line-height: 1.5;
  counter-increment: chain-counter;
}

.bu-chain li:last-child { border-bottom: none; }

.bu-chain li::before {
  content: counter(chain-counter);
  position: absolute;
  left: 0;
  top: 0.42rem;
  font-size: 0.55rem;
  font-weight: 700;
  color: var(--red);
  background: var(--offwhite);
  border: 1px solid var(--lgray);
  width: 16px;
  height: 16px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  line-height: 1;
  text-align: center;
}

/* ── Friction timing steps ── */
.bu-timing-grid {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 0;
  border: 1px solid var(--lgray);
  margin-bottom: 2rem;
  overflow: hidden;
}

.bu-timing-cell {
  padding: 1.5rem;
  border-right: 1px solid var(--lgray);
  text-align: center;
}

.bu-timing-cell:last-child { border-right: none; }
.bu-timing-cell--good { background: var(--black); }

.bu-timing-cell__label {
  font-size: 0.58rem;
  font-weight: 700;
  letter-spacing: 0.25em;
  text-transform: uppercase;
  margin-bottom: 0.5rem;
}

.bu-timing-cell--bad  .bu-timing-cell__label { color: var(--gray); }
.bu-timing-cell--good .bu-timing-cell__label { color: var(--red); }

.bu-timing-cell__title {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 0.4rem;
}

.bu-timing-cell--bad  .bu-timing-cell__title { color: var(--black); }
.bu-timing-cell--good .bu-timing-cell__title { color: var(--white); }

.bu-timing-cell__desc {
  font-size: 0.78rem;
  line-height: 1.6;
}

.bu-timing-cell--bad  .bu-timing-cell__desc { color: var(--gray); }
.bu-timing-cell--good .bu-timing-cell__desc { color: rgba(255,255,255,0.55); }

/* ── Big Secret callout ── */
.bu-big-callout {
  border: 1px solid var(--black);
  padding: 3rem 2.5rem;
  text-align: center;
  margin-bottom: 2rem;
}

.bu-big-callout__label {
  font-size: 0.58rem;
  font-weight: 700;
  letter-spacing: 0.3em;
  text-transform: uppercase;
  color: var(--red);
  margin-bottom: 1.25rem;
}

.bu-big-callout__text {
  font-size: clamp(1.1rem, 2.5vw, 1.6rem);
  font-weight: 300;
  color: var(--black);
  line-height: 1.4;
  max-width: 680px;
  margin: 0 auto 1rem;
}

.bu-big-callout__text strong { font-weight: 600; }

.bu-big-callout__sub {
  font-size: 0.83rem;
  color: var(--gray);
  max-width: 520px;
  margin: 0 auto;
  line-height: 1.75;
}

/* ── Responsive ── */
@media (max-width: 900px) {
  .bu-var-grid       { grid-template-columns: 1fr; }
  .bu-interact-grid  { grid-template-columns: 1fr; }
  .bu-scenario-grid  { grid-template-columns: 1fr; }
  .bu-timing-grid    { grid-template-columns: 1fr; }
  .bu-timing-cell    { border-right: none; border-bottom: 1px solid var(--lgray); }
  .bu-timing-cell:last-child { border-bottom: none; }
}

/* ================================================
   COURSE PAGE COMPONENTS (existing)
   ================================================ */

/* ── Wide card (spans both columns) ── */
.bu-oil-card--wide {
  grid-column: 1 / -1;
}

.bu-oil-card--wide .bu-oil-card__body {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0 2rem;
}

.bu-oil-card--wide .bu-oil-card__body > .bu-sub-label:first-child,
.bu-oil-card--wide .bu-oil-card__body > .bu-dot-list:first-of-type {
  grid-column: 1;
}

@media (max-width: 900px) {
  .bu-oil-card--wide .bu-oil-card__body { grid-template-columns: 1fr; }
}

/* ── Transition phase steps ── */
.bu-steps {
  display: flex;
  margin-bottom: 2rem;
}

.bu-step {
  flex: 1;
  border: 1px solid var(--lgray);
  padding: 1.25rem 1.5rem;
  background: var(--white);
  position: relative;
}

.bu-step + .bu-step { border-left: none; }

.bu-step__num {
  font-size: 0.58rem;
  font-weight: 700;
  letter-spacing: 0.28em;
  text-transform: uppercase;
  color: var(--red);
  margin-bottom: 0.35rem;
}

.bu-step__title {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--black);
  margin-bottom: 0.5rem;
}

.bu-step__desc {
  font-size: 0.8rem;
  color: var(--gray);
  line-height: 1.65;
}

@media (max-width: 600px) {
  .bu-steps { flex-direction: column; }
  .bu-step + .bu-step { border-left: 1px solid var(--lgray); border-top: none; }
}

/* ── Surface vs oil matrix ── */
.bu-matrix-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.8rem;
  margin-bottom: 2rem;
}

.bu-matrix-table th {
  font-size: 0.6rem;
  font-weight: 700;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--black);
  padding: 0.75rem 1rem;
  background: var(--offwhite);
  border: 1px solid var(--lgray);
  text-align: left;
}

.bu-matrix-table th:not(:first-child) { text-align: center; }

.bu-matrix-table td {
  padding: 0.75rem 1rem;
  border: 1px solid var(--lgray);
  vertical-align: middle;
  line-height: 1.5;
}

.bu-matrix-table td:first-child { font-weight: 600; white-space: nowrap; }
.bu-matrix-table td:not(:first-child) { text-align: center; color: var(--gray); }

.bu-matrix-table tr:hover td { background: var(--offwhite); }

/* ── Reference table type badges ── */
.bu-ref-table td:nth-child(3) {
  font-weight: 600;
  white-space: nowrap;
}

.bu-type-badge {
  display: inline-block;
  font-size: 0.58rem;
  font-weight: 700;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  padding: 0.2rem 0.55rem;
  white-space: nowrap;
}

.bu-type-badge--low     { background: #e8f4fd; color: #1a6fa8; }
.bu-type-badge--medium  { background: #fff4e0; color: #a06010; }
.bu-type-badge--high    { background: #fde8e8; color: #9c1111; }
.bu-type-badge--hybrid  { background: #ede8fd; color: #5a1a8a; }

/* ── Energy Retention Chart ── */
.bu-energy-section {
  border: 1px solid var(--lgray);
  padding: 1.5rem 1.5rem 1rem;
  background: var(--white);
  margin: 1.5rem 0;
}

.bu-energy-chart {
  display: flex;
  align-items: stretch;
  gap: 0.75rem;
  height: 110px;
  border-bottom: 2px solid var(--lgray);
  margin-bottom: 0.6rem;
}

.bu-energy-bar-wrap {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: flex-end;
}

.bu-energy-bar-wrap__val {
  font-size: 0.65rem;
  font-weight: 700;
  color: var(--black);
  margin-bottom: 0.2rem;
  line-height: 1;
}

.bu-energy-bar-wrap__fill {
  width: 100%;
  background: var(--red);
  opacity: 0.72;
}

.bu-energy-zone-names {
  display: flex;
  gap: 0.75rem;
}

.bu-energy-zone-name {
  flex: 1;
  font-size: 0.5rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--gray);
  text-align: center;
}

.bu-energy-desc {
  font-size: 0.78rem;
  color: var(--gray);
  line-height: 1.65;
  margin-top: 0.75rem;
}

.bu-energy-chart--pindown .bu-energy-bar-wrap__fill {
  background: var(--black);
  opacity: 0.45;
}

/* ── Responsive ── */
@media (max-width: 900px) {
  .bu-box-grid { grid-template-columns: 1fr; }
  .bu-oil-grid { grid-template-columns: 1fr; }
  .bu-prop-grid { grid-template-columns: 1fr 1fr; }
  .bu-compare-grid { grid-template-columns: 1fr; }
}

@media (max-width: 600px) {
  .bu-hero { padding: 2.5rem 1.25rem 2rem; }
  .bu-section { padding: 2.5rem 1.25rem; }
  .bu-breadcrumb { padding: 0.65rem 1.25rem; }
  .bu-prop-grid { grid-template-columns: 1fr; }
  .bu-ref-table { display: block; overflow-x: auto; -webkit-overflow-scrolling: touch; }
}