/* ===== Hero de sesión ===== */
.session-hero { padding: var(--space-5) 0 var(--space-4); border-bottom: 1.5px solid var(--blueprint); }
.session-hero__grid {
  display: grid; grid-template-columns: 1fr 0.9fr; gap: var(--space-4); align-items: start;
}
.session-hero__head .num {
  font-family: var(--font-display); font-weight: 700; font-size: 3.4rem; line-height: 1;
  color: var(--race-red);
}
.session-hero h1 { font-size: clamp(1.9rem, 4vw, 2.8rem); margin-top: 6px; }
.session-hero .quote { color: var(--dim); font-style: italic; max-width: 520px; font-size: 1.05rem; }
.session-hero .badges { display: flex; gap: 8px; flex-wrap: wrap; margin-top: var(--space-2); }

/* Pieza de referencia (isométrico + ficha) */
.session-hero__ref { display: grid; gap: var(--space-3); }
.part-fig {
  margin: 0; border: 1.5px solid var(--line-strong); border-radius: var(--radius-lg);
  background:
    repeating-linear-gradient(0deg, transparent, transparent calc(var(--grid-step) - 1px), rgba(15,42,67,0.045) calc(var(--grid-step) - 1px), rgba(15,42,67,0.045) var(--grid-step)),
    repeating-linear-gradient(90deg, transparent, transparent calc(var(--grid-step) - 1px), rgba(15,42,67,0.045) calc(var(--grid-step) - 1px), rgba(15,42,67,0.045) var(--grid-step)),
    var(--paper);
  box-shadow: 6px 6px 0 -1px var(--paper-3), 6px 6px 0 0 var(--line-strong);
}
.part-fig__caption {
  display: flex; justify-content: space-between; align-items: baseline; gap: 12px;
  padding: 9px var(--space-2); border-bottom: 1.5px solid var(--blueprint);
  font-family: var(--font-display); font-weight: 600; font-size: 0.8rem;
  letter-spacing: 0.08em; text-transform: uppercase; color: var(--blueprint);
}
.part-fig__draw { padding: var(--space-2); }
.part-fig__draw svg { display: block; width: 100%; height: auto; }
.part-fig__placeholder {
  display: flex; align-items: center; justify-content: center; text-align: center;
  min-height: 220px; padding: var(--space-3); color: var(--dim);
  font-family: var(--font-mono); font-size: 0.85rem;
}
/* Estilo de línea técnica compartido por los dibujos isométricos (parts.js) */
.part-fig__draw .ln { fill: none; stroke: var(--blueprint); stroke-width: 2; stroke-linejoin: round; stroke-linecap: round; }
.part-fig__draw .ln-2 { fill: none; stroke: var(--blueprint-2); stroke-width: 1.4; stroke-linejoin: round; stroke-linecap: round; }
.part-fig__draw .hole { fill: var(--paper); }
.part-fig__draw .cl { stroke: var(--race-red); stroke-width: 1; opacity: 0.6; fill: none; stroke-dasharray: 10 3 2 3; }
.part-fig__draw .dim-line { stroke: var(--race-red); stroke-width: 1.1; fill: none; }
.part-fig__draw .ext-line { stroke: var(--dim); stroke-width: 0.9; fill: none; }
.part-fig__draw .lead-line { stroke: var(--dim); stroke-width: 0.9; fill: none; }
.part-fig__draw .dim-txt { font-family: var(--font-mono); font-size: 14px; font-weight: 500; fill: var(--blueprint); }
.part-fig__draw .fill-soft { fill: rgba(15,42,67,0.05); stroke: none; }

/* Ficha de pieza (junto al isométrico) */
.spec-card {
  background: var(--paper-2); border: 1.5px solid var(--line-strong); border-radius: var(--radius-lg);
  padding: var(--space-3); display: flex; flex-direction: column;
}
.spec-card__eyebrow { font-family: var(--font-mono); font-size: 0.64rem; letter-spacing: 0.16em; text-transform: uppercase; color: var(--race-red); margin-bottom: 4px; }
.spec-card__title { font-family: var(--font-display); font-weight: 600; font-size: 1.1rem; text-transform: uppercase; letter-spacing: 0.02em; color: var(--blueprint); margin-bottom: 12px; padding-bottom: 10px; border-bottom: 1px solid var(--line-strong); }
.spec-list { display: grid; gap: 9px; font-family: var(--font-mono); font-size: 0.82rem; align-content: start; }
.spec-row { display: flex; justify-content: space-between; gap: 14px; align-items: baseline; }
.spec-k { color: var(--dim); white-space: nowrap; }
.spec-v { color: var(--ink); text-align: right; }
.spec-v .hl { color: var(--race-red); font-weight: 600; }
.spec-card__note { margin: 12px 0 0; font-size: 0.8rem; color: var(--dim); font-family: var(--font-body); }

/* ===== Secciones ===== */
.session-section { padding: var(--space-5) 0; }
.session-section h2 { font-size: 1.5rem; margin-bottom: var(--space-3); }
.session-section + .session-section { border-top: 1px solid var(--line); }

.concept { max-width: 760px; }
.concept p { font-size: 1.02rem; }
.concept code, .callout code { font-family: var(--font-mono); color: var(--race-red); background: var(--paper-3); padding: 1px 6px; border-radius: 3px; font-size: 0.9em; }
.concept .value-hl { color: var(--race-red); font-family: var(--font-mono); font-weight: 600; }
.concept .diagram { margin-top: var(--space-2); }

.teacher-note {
  margin-top: var(--space-3); border-left: 3px solid var(--race-red);
  background: var(--red-wash); border-radius: 0 var(--radius) var(--radius) 0;
  padding: var(--space-1) var(--space-2);
}
.teacher-note summary { cursor: pointer; color: var(--race-red); font-family: var(--font-mono); font-size: 0.8rem; letter-spacing: 0.02em; list-style: none; user-select: none; }
.teacher-note summary::-webkit-details-marker { display: none; }
.teacher-note[open] summary { margin-bottom: 8px; }
.teacher-note p { margin: 0; font-size: 0.92rem; color: var(--ink); }
.teacher-note p + p { margin-top: 6px; }

.reference-block { display: grid; gap: var(--space-3); margin-top: var(--space-2); }
.reference-block .formula-item .formula-label { color: var(--dim); font-size: 0.85rem; margin-bottom: 5px; }
.table-wrap { overflow-x: auto; }
.table-caption { color: var(--dim); font-size: 0.85rem; margin-bottom: 6px; }

.diagram { margin: 0; }
.diagram img { width: 100%; max-width: 440px; border-radius: var(--radius); border: 1.5px solid var(--line-strong); background: var(--paper); }
.diagram figcaption { margin-top: 6px; }
.diagram--wide img { max-width: 660px; display: block; }

.biblio { margin: 0; padding-left: 1.2em; color: var(--ink); }
.biblio li { margin-bottom: 6px; }

/* ===== Reto (criterio "lo lograste o no") ===== */
.reto {
  border: 1.5px solid var(--blueprint); border-top-width: 4px; border-radius: var(--radius-lg);
  background: var(--paper-2); padding: var(--space-4);
}
.reto__tag {
  display: inline-block; font-family: var(--font-mono); font-size: 0.66rem;
  letter-spacing: 0.16em; text-transform: uppercase; color: var(--paper);
  background: var(--race-red); padding: 3px 10px; border-radius: 2px; margin-bottom: var(--space-2);
}
.reto h2 { font-size: 1.5rem; margin-bottom: var(--space-2); }
.reto .checklist { margin-top: var(--space-2); }

/* ===== Nav prev/next ===== */
.session-nav { display: flex; justify-content: space-between; gap: var(--space-2); padding: var(--space-4) var(--space-3); flex-wrap: wrap; }

/* ===== Rieles laterales (pantallas anchas) ===== */
.side-rail { display: none; }
@media (min-width: 1360px) {
  #session-root { --max-width: clamp(960px, 40.6vw + 405px, 1120px); }
  .side-rail {
    display: flex; flex-direction: column;
    position: fixed; top: 120px; bottom: 32px; z-index: 5;
    width: clamp(120px, calc((100vw - var(--max-width)) / 2 - 48px), 250px);
    overflow: auto; scrollbar-width: none;
  }
  .side-rail::-webkit-scrollbar { display: none; }
  .side-rail--left  { right: calc(50% + (var(--max-width) / 2) + 20px); }
  .side-rail--right { left: calc(50% + (var(--max-width) / 2) + 20px); text-align: right; }
}
.side-rail__label {
  font-family: var(--font-mono); font-size: 0.68rem; letter-spacing: 0.14em;
  text-transform: uppercase; color: var(--dim); margin-bottom: 14px;
  padding-bottom: 10px; border-bottom: 1px solid var(--line-strong); flex-shrink: 0;
}

.spy { list-style: none; margin: 0; padding: 0; display: grid; gap: 2px; }
.spy a {
  display: block; padding: 8px 12px; border-left: 2px solid var(--line-strong);
  color: var(--dim); text-decoration: none; font-size: 0.84rem; line-height: 1.3;
  transition: color 0.15s ease, border-color 0.15s ease, background 0.15s ease;
}
.spy a:hover { color: var(--ink); background: var(--blueprint-wash); }
.spy a.is-active { color: var(--race-red); border-left-color: var(--race-red); background: var(--red-wash); font-weight: 500; }

.rail-progress { margin-top: auto; flex-shrink: 0; padding-top: var(--space-3); }
.rail-progress__label { font-family: var(--font-mono); font-size: 0.64rem; letter-spacing: 0.1em; text-transform: uppercase; color: var(--dim); margin-bottom: 6px; }
.rail-progress__track { height: 4px; border-radius: 2px; background: var(--line-strong); overflow: hidden; }
.rail-progress__fill { display: block; height: 100%; width: 0; background: var(--race-red); transition: width 0.15s linear; }

/* Riel derecho: ficha de cotas */
.rail-specs { display: grid; gap: 10px; font-family: var(--font-mono); font-size: 0.78rem; }
.rail-spec { display: flex; justify-content: space-between; gap: 10px; align-items: baseline; }
.side-rail--right .rail-spec { flex-direction: row-reverse; }
.rail-spec__k { color: var(--dim); }
.rail-spec__v { color: var(--blueprint); font-weight: 500; }
.rail-note { margin-top: var(--space-3); font-family: var(--font-body); font-size: 0.76rem; color: var(--dim); line-height: 1.4; }

/* ===== Responsive ===== */
@media (max-width: 900px) {
  .session-hero__grid { grid-template-columns: 1fr; gap: var(--space-3); }
  .session-hero__ref { max-width: 460px; }
}
@media (max-width: 640px) {
  .session-nav { flex-direction: column; }
  .session-nav .btn { justify-content: center; }
}