/* ==========================================================================
   Core Pillars
   Six disciplines rendered as tagged nodes off a single-line busbar rail —
   the same visual language substation engineers use for single-line
   diagrams (SLDs). Each node fades in + its tap-off line "energizes" as it
   scrolls into view. JS (main.js) adds .is-visible via IntersectionObserver
   and staggers via --i (see pillar-node markup).
   ========================================================================== */

.pillars {
  position: relative;
  background: var(--color-bg);
}

.pillars__head {
  max-width: 640px;
  margin-inline: auto;
  text-align: center;
  margin-block-end: var(--space-6);
}

.pillars__head h2 {
  margin-block-start: var(--space-2);
  font-size: var(--text-xl);
}

.pillars__head p {
  margin-block-start: var(--space-2);
  color: var(--color-text-muted);
  font-size: var(--text-md);
}

/* ---- Rail + grid ---- */
.pillar-rail {
  position: relative;
}

/* The vertical spine on desktop; becomes a left-aligned spine on mobile */
.pillar-rail::before {
  content: "";
  position: absolute;
  inset-inline-start: 50%;
  inset-block: 0;
  width: 2px;
  background: repeating-linear-gradient(
    to bottom,
    var(--color-border) 0,
    var(--color-border) 8px,
    transparent 8px,
    transparent 16px
  );
  transform: translateX(-50%);
}

.pillar-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-5) var(--space-4);
  position: relative;
}

.pillar-node {
  --i: 0;
  position: relative;
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  padding: var(--space-4);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);

  /* scroll-reveal, staggered by node index */
  opacity: 0;
  transform: translateY(var(--reveal-distance));
  transition: opacity var(--reveal-duration) var(--ease-out),
              transform var(--reveal-duration) var(--ease-out),
              box-shadow var(--duration-fast) var(--ease-out),
              border-color var(--duration-fast) var(--ease-out);
  transition-delay: calc(var(--i) * 90ms);
}

.pillar-node.is-visible {
  opacity: 1;
  transform: translateY(0);
}

.pillar-node:hover {
  border-color: var(--color-maroon);
  box-shadow: var(--shadow-md);
}

/* tap-off connector dot, aligned to the central rail on desktop */
.pillar-node::after {
  content: "";
  position: absolute;
  inset-block-start: var(--space-4);
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--color-porcelain);
  border: 2px solid var(--color-maroon);
  transition: background var(--duration-base) var(--ease-out);
}

.pillar-node.is-visible::after {
  background: var(--color-gold);
  border-color: var(--color-gold);
}

.pillar-node__img {
  width: 100%;
  height: 140px;
  object-fit: cover;
  border-radius: var(--radius-sm);
  margin-block-end: var(--space-1);
  filter: grayscale(35%);
  transition: filter var(--duration-base) var(--ease-out);
}

.pillar-node:hover .pillar-node__img,
.pillar-node.is-visible .pillar-node__img {
  filter: grayscale(0%);
}

.pillar-node__tag {
  display: inline-flex;
  align-self: flex-start;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: var(--tracking-wider);
  color: var(--color-maroon);
  background: var(--color-maroon-tint);
  padding: 0.2rem 0.6rem;
  border-radius: var(--radius-pill);
}

.pillar-node__title {
  font-size: var(--text-lg);
  font-weight: 600;
}

.pillar-node__desc {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: var(--leading-snug);
}

@media (max-width: 900px) {
  .pillar-grid { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 640px) {
  .pillar-grid { grid-template-columns: 1fr; }
  .pillar-rail::before { inset-inline-start: 0; }
  .pillar-node::after { inset-inline-start: -21px; }
}

@media (prefers-reduced-motion: reduce) {
  .pillar-node {
    opacity: 1;
    transform: none;
    transition: border-color var(--duration-fast) var(--ease-out),
                box-shadow var(--duration-fast) var(--ease-out);
  }
}