/**
 * training.css
 * ─────────────────────────────────────────────────────────────
 * PURPOSE: Styles for "Training Epochs" — the education
 *          timeline section. Each epoch represents a learning
 *          milestone styled as an ML training run.
 *
 * LOGIC: Vertical timeline with alternating cards left/right
 *        on desktop, single-column on mobile.
 *        Cards expand/collapse on click (JS in timeline.js).
 *        Active epoch glows with the primary brand color.
 *
 * CUSTOMIZATION: Add new epochs in index.html.
 *                Adjust the connector line color via --color-primary.
 * ─────────────────────────────────────────────────────────────
 */

#training { background: var(--color-bg); }

/* ── TIMELINE WRAPPER ──────────────────────────────────────── */
.timeline {
  position: relative;
  max-width: 900px;
  margin-inline: auto;
  padding-block: var(--space-4);
}

/* Vertical center line */
.timeline::before {
  content: '';
  position: absolute;
  left: 50%;
  top: 0; bottom: 0;
  width: 2px;
  transform: translateX(-50%);
  background: linear-gradient(180deg,
    transparent,
    var(--color-primary) 10%,
    var(--color-primary) 90%,
    transparent
  );
  opacity: 0.4;
}

/* ── EPOCH ITEM ────────────────────────────────────────────── */
.epoch {
  display: grid;
  grid-template-columns: 1fr 60px 1fr;
  gap: var(--space-4);
  align-items: start;
  margin-bottom: var(--space-10);
  position: relative;
}

/* Alternate card side */
.epoch:nth-child(even) .epoch__card { grid-column: 3; }
.epoch:nth-child(even) .epoch__node { grid-column: 2; }
.epoch:nth-child(even) .epoch__spacer { grid-column: 1; grid-row: 1; }

.epoch:nth-child(odd) .epoch__card  { grid-column: 1; }
.epoch:nth-child(odd) .epoch__node  { grid-column: 2; }

/* ── EPOCH NODE (center dot) ───────────────────────────────── */
.epoch__node {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-2);
  position: relative;
  z-index: 1;
}

.epoch__dot {
  width: 48px; height: 48px;
  border-radius: 50%;
  background: var(--color-surface);
  border: 3px solid var(--color-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: var(--weight-bold);
  color: var(--color-primary);
  box-shadow: 0 0 0 6px rgba(139, 92, 246, 0.1);
  transition: all var(--transition-base);
  cursor: default;
  flex-shrink: 0;
}

.epoch.active .epoch__dot {
  background: var(--color-primary);
  color: white;
  box-shadow: 0 0 0 6px rgba(139, 92, 246, 0.2), var(--shadow-glow);
  animation: glow-pulse 2s infinite;
}

.epoch__number-label {
  font-family: var(--font-mono);
  font-size: 9px;
  color: var(--color-primary);
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

/* ── EPOCH CARD ────────────────────────────────────────────── */
.epoch__card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  overflow: hidden;
  transition: all var(--transition-base);
  cursor: pointer;
}

.epoch__card:hover {
  border-color: rgba(139, 92, 246, 0.4);
  box-shadow: var(--shadow-card);
  transform: translateY(-2px);
}

.epoch.active .epoch__card {
  border-color: rgba(139, 92, 246, 0.5);
  box-shadow: 0 0 0 1px rgba(139, 92, 246, 0.2), var(--shadow-card);
}

/* Card header */
.epoch__card-header {
  padding: var(--space-4) var(--space-5);
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--space-3);
}

.epoch__card-icon {
  font-size: 24px;
  flex-shrink: 0;
}

.epoch__card-meta {
  flex: 1;
}

.epoch__year {
  font-family: var(--font-mono);
  font-size: 10px;
  color: var(--color-primary);
  letter-spacing: 0.15em;
  text-transform: uppercase;
  margin-bottom: var(--space-1);
}

.epoch__title {
  font-size: var(--text-base);
  font-weight: var(--weight-bold);
  color: var(--color-text);
  margin-bottom: var(--space-1);
  line-height: 1.3;
}

.epoch__institution {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
}

/* Expand toggle */
.epoch__toggle {
  width: 28px; height: 28px;
  border-radius: 50%;
  background: rgba(139, 92, 246, 0.1);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-primary);
  font-size: 14px;
  transition: all var(--transition-base);
  flex-shrink: 0;
}

.epoch.expanded .epoch__toggle {
  transform: rotate(180deg);
  background: rgba(139, 92, 246, 0.2);
}

/* Card body — expandable */
.epoch__card-body {
  max-height: 0;
  overflow: hidden;
  transition: max-height var(--transition-slow);
}

.epoch.expanded .epoch__card-body {
  max-height: 400px;
}

.epoch__card-body-inner {
  padding: var(--space-4) var(--space-5);
  border-top: 1px solid var(--color-border);
}

.epoch__description {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.7;
  margin-bottom: var(--space-4);
}

/* Skill chips earned in this epoch */
.epoch__skills {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin-bottom: var(--space-4);
}

.epoch__skill-chip {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--color-primary);
  background: rgba(139, 92, 246, 0.1);
  border: 1px solid rgba(139, 92, 246, 0.2);
  padding: 2px var(--space-2);
  border-radius: var(--radius-sm);
}

/* Score / grade row */
.epoch__grade {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-4);
  background: rgba(139, 92, 246, 0.06);
  border-radius: var(--radius-lg);
}

.epoch__grade-label {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--color-text-faint);
  flex: 1;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.epoch__grade-value {
  font-family: var(--font-mono);
  font-weight: var(--weight-bold);
  color: var(--color-success);
  font-size: var(--text-sm);
}

/* Spacer column (pushes card to correct side) */
.epoch__spacer { /* empty */ }