/* Scene 3 — Three stages: encoder → bottleneck → decoder.

   Five panels in a single row:
     [input] -> [encoder box] -> [bottleneck] -> [decoder box] -> [segmentation]

   Stages and arrows light up progressively as the user steps through; the
   bottleneck and segmentation panels start dim and fade in as their
   producing stage activates. */

.s3-root { padding: 0 4px 32px; }
.s3-wrap {
  max-width: 1180px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 22px;
}

/* ---- Hero ----------------------------------------------------------- */
.s3-hero h1 { margin-bottom: 4px; }
.s3-hero .subtitle {
  font-style: italic;
  color: var(--ink-secondary);
  margin: 0;
}

.s3-mini-host { align-self: flex-start; }

/* ---- Pipeline (the big diagram) ------------------------------------ */
.s3-pipeline {
  display: flex;
  flex-direction: row;
  align-items: center;
  justify-content: center;
  gap: 14px;
  flex-wrap: wrap;
  padding: 22px 16px;
  background: var(--card-bg);
  border: 1px solid var(--rule);
  border-radius: 6px;
}

/* Tensor panels (input, bottleneck, segmentation). */
.s3-panel {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  opacity: 1;
  transition: opacity 0.25s;
}
.s3-panel-head {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1px;
  text-align: center;
}
.s3-panel-name {
  font-family: "Iowan Old Style", Palatino, Georgia, serif;
  font-style: italic;
  font-size: 14px;
  color: var(--ink);
  font-weight: 500;
}
.s3-panel-sub {
  font-family: "SF Mono", Menlo, monospace;
  font-size: 10.5px;
  color: var(--ink-secondary);
  letter-spacing: 0.02em;
}

.s3-panel-body {
  border: 1px solid var(--rule);
  border-radius: 4px;
  background: var(--bg);
  display: flex;
  align-items: center;
  justify-content: center;
  flex: 0 0 auto;
}
.s3-panel-body canvas { display: block; }

/* Bottleneck panel deserves a small visual cue: a slightly recessed
   border tint that says "this is the named thing". */
.s3-bottleneck .s3-panel-body {
  border: 1.5px solid var(--rule);
}
.s3-bottleneck.s3-revealed .s3-panel-body {
  border-color: var(--cnn-purple, #7a5c8c);
  box-shadow: 0 0 0 2px rgba(122, 92, 140, 0.12);
}
.s3-bottleneck.s3-revealed .s3-panel-name {
  color: var(--cnn-purple, #7a5c8c);
  font-weight: 600;
  font-style: normal;
}

/* Bottleneck and segmentation start dim; brighten when revealed. */
.s3-bottleneck:not(.s3-revealed),
.s3-seg:not(.s3-revealed) {
  opacity: 0.45;
}

/* Stage boxes (encoder, decoder). */
.s3-stage {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 4px;
  width: 110px;
  height: 88px;
  padding: 10px 8px;
  background: var(--bg);
  border: 1.5px dashed var(--rule);
  border-radius: 6px;
  text-align: center;
  transition: border-color 0.25s, background 0.25s, color 0.25s;
}
.s3-stage-name {
  font-family: "Iowan Old Style", Palatino, Georgia, serif;
  font-style: italic;
  font-size: 16px;
  color: var(--ink-secondary);
  font-weight: 500;
}
.s3-stage-sub {
  font-family: "SF Mono", Menlo, monospace;
  font-size: 10px;
  color: var(--ink-secondary);
  line-height: 1.3;
}

.s3-stage.s3-lit {
  border-style: solid;
  background: var(--card-bg);
}
.s3-enc.s3-lit {
  border-color: var(--cnn-pos);
  color: var(--cnn-pos);
}
.s3-enc.s3-lit .s3-stage-name { color: var(--cnn-pos); }
.s3-dec.s3-lit {
  border-color: var(--cnn-accent, #c08a3e);
  color: var(--cnn-accent, #c08a3e);
}
.s3-dec.s3-lit .s3-stage-name { color: var(--cnn-accent, #c08a3e); }

/* Arrows. */
.s3-arrow {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 2px;
  color: var(--rule);
  transition: color 0.25s;
  flex: 0 0 auto;
}
.s3-arrow-shaft {
  display: inline-block;
  width: 22px;
  height: 1.5px;
  background: currentColor;
}
.s3-arrow-head {
  font-size: 11px;
  line-height: 1;
  margin-left: -4px;
}
.s3-arrow.s3-lit { color: var(--ink-secondary); }

/* ---- Sample picker ------------------------------------------------- */
.s3-selector {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 14px;
  background: var(--card-bg);
  border: 1px solid var(--rule);
  border-radius: 4px;
}
.s3-selector-label {
  font-size: 11px;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--ink-secondary);
  font-family: "SF Mono", Menlo, monospace;
}
.s3-selector-row {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}
.s3-thumb {
  background: var(--bg);
  border: 1.5px solid var(--rule);
  border-radius: 3px;
  padding: 3px;
  cursor: pointer;
  display: block;
  line-height: 0;
  transition: border-color 0.15s;
}
.s3-thumb:hover { border-color: var(--ink-secondary); }
.s3-thumb.active { border-color: var(--cnn-pos); }
.s3-thumb-host { display: block; line-height: 0; }
.s3-thumb-host canvas { display: block; }

/* ---- Caption + explainer ------------------------------------------ */
.s3-caption {
  text-align: center;
  margin: 0;
  max-width: 880px;
  margin-left: auto;
  margin-right: auto;
}

.s3-explainer {
  background: var(--card-bg);
  border: 1px solid var(--rule);
  border-left: 3px solid var(--cnn-purple, #7a5c8c);
  border-radius: 4px;
  padding: 16px 22px;
  opacity: 0.35;
  transition: opacity 0.3s;
  max-width: 820px;
  margin: 0 auto;
}
.s3-explainer.s3-revealed { opacity: 1; }
.s3-explainer-title {
  font-family: "SF Mono", Menlo, monospace;
  font-size: 11px;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--cnn-purple, #7a5c8c);
  margin: 0 0 8px;
}
.s3-explainer-body {
  font-family: "Iowan Old Style", Palatino, Georgia, serif;
  font-size: 15px;
  line-height: 1.6;
  color: var(--ink);
  margin: 0 0 8px;
}
.s3-explainer-body:last-child { margin-bottom: 0; }
.s3-explainer-body strong { font-weight: 600; }
.s3-explainer-body em { font-style: italic; color: var(--ink-secondary); }

/* ---- Controls ------------------------------------------------------ */
.s3-controls { margin-top: 4px; }
#s3-step { width: 200px; }

/* ---- Narrow viewports --------------------------------------------- */
@media (max-width: 1080px) {
  .s3-pipeline { gap: 10px; padding: 18px 10px; }
  .s3-stage { width: 96px; height: 80px; padding: 8px 6px; }
  .s3-arrow-shaft { width: 14px; }
}
@media (max-width: 820px) {
  .s3-pipeline {
    /* On a narrow screen the row is too wide; let panels wrap and rely
       on the lit/dim state to keep the reading order clear. */
    flex-direction: row;
  }
  .s3-arrow { transform: none; }
}