/* ─── Design Tokens ──────────────────────────────────────── */
:root {
  --bg: #000000; --panel: #111111;
  --border: rgba(201,164,76,0.12); --border-h: rgba(201,164,76,0.28);
  --text: #F4F1E8; --text-sec: #E8E4DA; --text-muted: #CFC9BC;
  --gold: #C9A44C; --gold-glow: rgba(201,164,76,0.22);
  --font-serif: 'Cinzel Decorative', serif;
  --font-sans: 'DM Sans', sans-serif;
  --font-tech: 'Space Grotesk', sans-serif;
}
html { scroll-behavior: smooth; }
body { background: var(--bg); color: var(--text); font-family: var(--font-sans); overflow-x: hidden; }
.sk-main { margin-top: 0; }
.sk-container { max-width: 1180px; margin: 0 auto; padding: clamp(3rem,7vw,6rem) clamp(1.25rem,4vw,3rem); }

.sk-eyebrow { display: block; font-family: var(--font-tech); font-size: 0.72rem; font-weight: 600; text-transform: uppercase; letter-spacing: 0.18em; color: var(--gold); margin-bottom: 0.75rem; }
.sk-sec-title { font-family: var(--font-serif); font-size: clamp(2rem,4vw,3.25rem); font-weight: 700; color: var(--text); margin: 0 0 1.5rem; line-height: 1.15; }
.sk-hero__subtitle { font-family: var(--font-tech); font-size: clamp(0.85rem,1.8vw,1.1rem); text-transform: uppercase; letter-spacing: 0.15em; color: var(--gold); margin-bottom: 1.5rem; }
.sk-sec-lead { font-size: clamp(1.05rem,2vw,1.2rem); line-height: 1.65; color: var(--text-sec); max-width: 780px; margin-bottom: 3rem; }
.sk-lead { font-size: 1.2rem; line-height: 1.6; color: var(--text); font-weight: 600; margin-bottom: 1.1rem; }
.sk-body-text { font-size: 1rem; line-height: 1.7; color: var(--text-sec); margin-bottom: 1rem; }
.sk-blockquote { border-left: 2px solid var(--gold); padding: 0.8rem 1.5rem; margin: 2rem 0 0; font-style: italic; font-size: 1.05rem; color: var(--text-sec); }
.sk-hero-text { font-size: 1rem; line-height: 1.7; color: var(--text-sec); margin-bottom: 1.2rem; }
.sk-hero-text strong { color: var(--text); }
.sk-back-link { display: inline-block; font-family: var(--font-tech); font-size: 0.72rem; font-weight: 600; text-transform: uppercase; letter-spacing: 0.1em; color: var(--text-muted); text-decoration: none; margin-bottom: 2rem; transition: color 240ms ease; }
.sk-back-link:hover { color: var(--gold); }

.sk-hero { position: relative; min-height: 100vh; padding-top: 72px; overflow: hidden; background: var(--bg); border-bottom: 1px solid var(--border); }

.sk-hero__video {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
  z-index: 0;
}

.sk-hero__overlay {
  position: absolute;
  inset: 0;
  background: radial-gradient(circle at 50% 40%, rgba(0, 0, 0,0.38) 0%, rgba(0, 0, 0,0.80) 100%);
  z-index: 1;
}

.sk-hero > .sk-container { position: relative; z-index: 2; }

.sk-chess-section { border-top: 1px solid var(--border); background: var(--bg); }
.sk-chess-section.alt-bg { background: #000000; }
.sk-hero-grid { display: grid; grid-template-columns: 1.1fr 1fr; gap: clamp(2rem,5vw,4.5rem); align-items: center; }

/* ─── Chess Board ────────────────────────────────────────── */
.sk-chess-board-wrap { display: flex; flex-direction: column; gap: 0.8rem; }
.chess-board-header { display: flex; justify-content: space-between; align-items: center; }
.chess-board-label { font-family: var(--font-tech); font-size: 0.62rem; font-weight: 700; letter-spacing: 0.12em; text-transform: uppercase; color: var(--text-muted); }
.sk-board-select {
  background: #121212;
  border: 1px solid var(--border);
  color: var(--gold);
  font-family: var(--font-tech);
  font-size: 0.65rem;
  font-weight: 700;
  text-transform: uppercase;
  padding: 0.35rem 0.6rem;
  border-radius: 0;
  outline: none;
  cursor: pointer;
  letter-spacing: 0.05em;
  transition: all 200ms ease;
}
.sk-board-select:hover {
  border-color: var(--gold);
  box-shadow: 0 0 10px rgba(201,164,76,0.15);
}
.chess-board {
  display: grid;
  grid-template-columns: repeat(8,1fr);
  border: 1px solid rgba(201,164,76,0.2);
  border-radius: 0;
  overflow: hidden;
  box-shadow: 0 20px 55px rgba(0,0,0,0.65);
  aspect-ratio: 1;
}
.chess-cell {
  aspect-ratio: 1;
  display: flex; align-items: center; justify-content: center;
  position: relative; cursor: default;
  transition: all 200ms ease;
}
.chess-cell.light { background: #e6dfcf; color: #161512; }
.chess-cell.dark  { background: #7e7058; color: #f4f1e8; }
.chess-cell.has-piece { cursor: pointer; }
.chess-cell.has-piece:hover { background: rgba(201, 164, 76, 0.15); }

/* Selected & Move states */
.chess-cell.selected {
  background: rgba(201, 164, 76, 0.45) !important;
  box-shadow: inset 0 0 10px rgba(201, 164, 76, 0.6);
}
.chess-cell.correct-move {
  background: rgba(46, 204, 113, 0.45) !important;
  box-shadow: inset 0 0 10px rgba(46, 204, 113, 0.6);
}
.chess-cell.wrong-move {
  background: rgba(231, 76, 60, 0.45) !important;
  box-shadow: inset 0 0 10px rgba(231, 76, 60, 0.6);
  animation: chessShake 0.4s ease;
}
.chess-cell.highlight-move::after {
  content: '';
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: rgba(0, 0, 0, 0.35);
  position: absolute;
  pointer-events: none;
}

@keyframes chessShake {
  0%, 100% { transform: translateX(0); }
  25% { transform: translateX(-4px); }
  75% { transform: translateX(4px); }
}

/* Standard Chess Pieces */
.chess-piece-img {
  width: 82%;
  height: 82%;
  user-select: none;
  pointer-events: none;
  transition: transform 200ms ease, filter 200ms ease;
  filter: drop-shadow(0 2px 4px rgba(0, 0, 0, 0.25));
}
.chess-cell.has-piece:hover .chess-piece-img {
  transform: scale(1.08);
  filter: drop-shadow(0 4px 8px rgba(0, 0, 0, 0.35));
}

.chess-annotation {
  background: #000000;
  border: 1px solid var(--border);
  border-left: 2px solid var(--gold);
  border-radius: 0;
  padding: 0.9rem 1.2rem;
  min-height: 52px;
  display: flex; align-items: center;
}
.annotation-prompt { font-family: var(--font-tech); font-size: 0.72rem; color: var(--text-muted); }
.annotation-text { font-family: var(--font-tech); font-size: 0.78rem; color: var(--text-sec); }
.text-danger { color: #e74c3c !important; }
.text-success { color: #2ecc71 !important; }

/* ─── Strategic Profile Grid ─────────────────────────────── */
.sk-chess-profile-grid {
  display: grid;
  grid-template-columns: 320px 1fr;
  gap: 2.5rem;
  margin-top: 1.5rem;
}

.profile-rating-card {
  background: linear-gradient(135deg, #000000 0%, #000000 100%);
  border: 1px solid var(--border);
  border-radius: 0;
  padding: 2.2rem 1.8rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  box-shadow: 0 20px 45px rgba(0,0,0,0.6);
  position: relative;
  overflow: hidden;
}

.profile-rating-card::before {
  content: '';
  position: absolute;
  top: -50%;
  left: -50%;
  width: 200%;
  height: 200%;
  background: radial-gradient(circle, rgba(201, 164, 76, 0) 0%, transparent 70%);
  pointer-events: none;
}

.rating-badge {
  font-family: var(--font-tech);
  font-size: 0.62rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  color: var(--text-muted);
  border: 1px solid rgba(255,255,255,0.06);
  padding: 0.3rem 0.65rem;
  border-radius: 0;
  background: rgba(255,255,255,0.01);
}

.rating-num {
  font-family: var(--font-tech);
  font-size: 4rem;
  font-weight: 700;
  color: var(--gold);
  line-height: 1;
  margin: 1.5rem 0 0.5rem;
  text-shadow: 0 0 25px rgba(201,164,76,0.3);
  letter-spacing: -0.02em;
}

.rating-rank {
  font-family: var(--font-tech);
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-sec);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 1.2rem;
}

.rating-desc {
  font-size: 0.85rem;
  line-height: 1.6;
  color: var(--text-muted);
  margin: 0 0 2rem;
}

.rating-status-row {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-top: auto;
  border-top: 1px solid rgba(255,255,255,0.05);
  width: 100%;
  padding-top: 1.2rem;
  justify-content: center;
}

.status-text {
  font-family: var(--font-tech);
  font-size: 0.6rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  color: #2ecc71;
}

.profile-stats-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.25rem;
}

.profile-stat-card {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 0;
  padding: 1.6rem;
  display: flex;
  gap: 1.2rem;
  align-items: flex-start;
  transition: all 250ms ease;
}

.profile-stat-card:hover {
  border-color: var(--border-h);
  box-shadow: 0 10px 25px rgba(0,0,0,0.3);
  transform: translateY(-2px);
}

.stat-icon {
  font-size: 1.5rem;
  line-height: 1;
  background: rgba(201,164,76,0.06);
  border: 1px solid rgba(201,164,76,0.12);
  width: 44px;
  height: 44px;
  border-radius: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.stat-info {
  display: flex;
  flex-direction: column;
  gap: 0.2rem;
}

.stat-label {
  font-family: var(--font-tech);
  font-size: 0.65rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
}

.stat-value {
  font-family: var(--font-tech);
  font-size: 1rem;
  font-weight: 600;
  color: var(--text);
}

.stat-desc {
  font-size: 0.8rem;
  line-height: 1.5;
  color: var(--text-muted);
  margin: 0.3rem 0 0;
}

/* ─── Lesson Cards ───────────────────────────────────────── */
.sk-lesson-cards { display: grid; grid-template-columns: repeat(2,1fr); gap: 1.5rem; margin-top: 1rem; }
.lesson-card {
  background: var(--panel); border: 1px solid var(--border); border-radius: 0;
  padding: 2.2rem 1.8rem; position: relative; overflow: hidden;
  transition: border-color 300ms ease, transform 280ms ease, box-shadow 300ms ease;
}
.lesson-card::before {
  content: ''; position: absolute; top: 0; left: 0; bottom: 0; width: 2px;
  background: var(--gold); opacity: 0; transition: opacity 300ms ease;
}
.lesson-card:hover { border-color: var(--border-h); transform: translateY(-2px); box-shadow: 0 20px 50px rgba(0,0,0,0.5); }
.lesson-card:hover::before { opacity: 1; }
.lc-index { font-family: var(--font-tech); font-size: 1.6rem; font-weight: 700; color: rgba(201,164,76,0.18); margin-bottom: 1rem; display: block; }
.lc-title { font-family: var(--font-tech); font-size: 1.1rem; font-weight: 700; color: var(--text); margin: 0 0 1rem; }
.lc-copy { font-size: 0.92rem; line-height: 1.65; color: var(--text-sec); margin: 0 0 1.5rem; }
.lc-transfer { font-family: var(--font-tech); font-size: 0.65rem; font-weight: 600; text-transform: uppercase; letter-spacing: 0.08em; color: var(--gold); background: rgba(201,164,76,0.06); padding: 0.5rem 0.8rem; border-radius: 0; }

/* ─── Chess Simulations Dashboard ────────────────────────── */
.sk-sim-dashboard {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 0;
  overflow: hidden;
  box-shadow: 0 25px 55px rgba(0,0,0,0.5);
  margin-top: 1.5rem;
}

.sim-tabs {
  display: flex;
  background: #000000;
  border-bottom: 1px solid var(--border);
  overflow-x: auto;
}

.sim-tab-btn {
  flex: 1;
  background: transparent;
  border: none;
  border-right: 1px solid var(--border);
  padding: 1.2rem 1rem;
  color: var(--text-muted);
  font-family: var(--font-tech);
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  cursor: pointer;
  transition: all 250ms ease;
  white-space: nowrap;
  outline: none;
  text-align: center;
}

.sim-tab-btn:last-child {
  border-right: none;
}

.sim-tab-btn:hover {
  color: var(--text-sec);
  background: rgba(255,255,255,0.02);
}

.sim-tab-btn.active {
  color: var(--gold);
  background: rgba(201,164,76,0.04);
  box-shadow: inset 0 -2px 0 var(--gold);
}

.sim-content-wrapper {
  display: grid;
  grid-template-columns: 320px 1fr;
  min-height: 480px;
}

.sim-controls {
  padding: 1.8rem;
  border-right: 1px solid var(--border);
  background: #000000;
  display: flex;
  flex-direction: column;
}

.sim-control-panel {
  display: none;
  flex-direction: column;
  gap: 1.5rem;
  height: 100%;
}

.sim-control-panel.active {
  display: flex;
}

.sim-panel-title {
  font-family: var(--font-tech);
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text);
  margin: 0 0 0.2rem;
}

.sim-panel-desc {
  font-size: 0.8rem;
  line-height: 1.5;
  color: var(--text-muted);
  margin: 0;
}

.sim-metrics {
  background: #000000;
  border: 1px solid var(--border);
  border-radius: 0;
  padding: 1.2rem;
  display: flex;
  flex-direction: column;
  gap: 0.8rem;
  margin-top: auto;
}

.metric-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 1px solid rgba(255,255,255,0.04);
  padding-bottom: 0.5rem;
}

.metric-row:last-of-type {
  border-bottom: none;
  padding-bottom: 0;
}

.metric-lbl {
  font-family: var(--font-tech);
  font-size: 0.65rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
}

.metric-val {
  font-family: var(--font-tech);
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--text);
}

.metric-comparison {
  font-size: 0.75rem;
  line-height: 1.4;
  color: var(--gold);
  border-top: 1px dashed rgba(201,164,76,0.15);
  padding-top: 0.6rem;
  margin-top: 0.2rem;
}

.sim-viewport {
  background: #000000;
  position: relative;
  display: flex;
  flex-direction: column;
}

.viewport-panel {
  display: none;
  flex-direction: column;
  flex: 1;
  padding: 1.5rem;
  position: relative;
}

.viewport-panel.active {
  display: flex;
}

.viewport-title-bar {
  font-family: var(--font-tech);
  font-size: 0.62rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  color: var(--text-muted);
  text-transform: uppercase;
  margin-bottom: 1rem;
}

/* Tree Sim Viewport Styling */
.tree-canvas-container {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 280px;
}

.sim-svg {
  width: 100%;
  height: 100%;
  max-height: 300px;
}

.logarithmic-scale-container {
  margin-top: auto;
  padding-top: 1.5rem;
  border-top: 1px solid rgba(255,255,255,0.05);
}

.log-scale-label {
  font-family: var(--font-tech);
  font-size: 0.6rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  margin-bottom: 0.8rem;
  text-align: center;
}

.log-scale-bar {
  height: 4px;
  background: rgba(255,255,255,0.08);
  border-radius: 2px;
  position: relative;
  margin-bottom: 1.5rem;
}

.log-scale-indicator {
  width: 12px;
  height: 12px;
  background: var(--gold);
  border-radius: 50%;
  position: absolute;
  top: 50%;
  transform: translate(-50%, -50%);
  box-shadow: 0 0 10px var(--gold);
  transition: left 300ms cubic-bezier(0.25, 0.46, 0.45, 0.94);
}

.log-scale-markers {
  position: relative;
  display: flex;
  justify-content: space-between;
  margin-top: 8px;
}

.log-scale-markers .marker {
  font-family: var(--font-tech);
  font-size: 0.58rem;
  color: var(--text-muted);
  position: absolute;
  transform: translateX(-50%);
  cursor: help;
}

.log-scale-markers .marker::after {
  content: attr(data-tooltip);
  position: absolute;
  bottom: 180%;
  left: 50%;
  transform: translateX(-50%) scale(0.8);
  background: #111;
  border: 1px solid var(--border);
  color: var(--text);
  padding: 0.25rem 0.45rem;
  font-size: 0.55rem;
  border-radius: 0;
  white-space: nowrap;
  opacity: 0;
  pointer-events: none;
  transition: all 200ms ease;
  z-index: 10;
}

.log-scale-markers .marker:hover::after {
  opacity: 1;
  transform: translateX(-50%) scale(1);
}

/* Chessboard Sim Viewport Styling */
.mini-chessboard-wrap {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
}

.mini-chessboard {
  display: grid;
  grid-template-columns: repeat(8, 1fr);
  width: 280px;
  height: 280px;
  border: 2px solid rgba(201,164,76,0.25);
  border-radius: 0;
  overflow: hidden;
  box-shadow: 0 15px 35px rgba(0,0,0,0.6);
}

.mini-cell {
  aspect-ratio: 1;
  position: relative;
  transition: all 300ms ease;
}

.mini-cell.light {
  background: #3a352a;
}

.mini-cell.dark {
  background: #1e1b15;
}

.mini-cell.active-sq {
  background: var(--gold) !important;
  box-shadow: 0 0 15px var(--gold);
  z-index: 5;
  animation: cellPulse 1.5s infinite alternate;
}

.mini-cell.highlighted-sq {
  background: rgba(201, 164, 76, 0.4);
}

@keyframes cellPulse {
  0% { transform: scale(1); box-shadow: 0 0 10px var(--gold); }
  100% { transform: scale(1.05); box-shadow: 0 0 20px var(--gold); }
}

/* Pruning Sim Viewport Styling */
.pruning-visualizer-container {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
  flex: 1;
}

.comparison-charts {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.chart-group {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

.chart-label {
  font-family: var(--font-tech);
  font-size: 0.62rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-sec);
}

.chart-bar-container {
  height: 22px;
  background: rgba(255,255,255,0.03);
  border: 1px solid rgba(255,255,255,0.06);
  border-radius: 0;
  position: relative;
  overflow: hidden;
}

.chart-bar {
  height: 100%;
  width: 0%; /* updated by JS */
  transition: width 400ms cubic-bezier(0.25, 0.46, 0.45, 0.94);
}

.unpruned-bar {
  background: linear-gradient(90deg, #e74c3c, #c0392b);
}

.pruned-bar {
  background: linear-gradient(90deg, var(--gold), #9e7d32);
}

.chart-val-overlay {
  position: absolute;
  right: 10px;
  top: 50%;
  transform: translateY(-50%);
  font-family: var(--font-tech);
  font-size: 0.68rem;
  font-weight: 700;
  color: var(--text);
  pointer-events: none;
}

.prune-tree-box {
  flex: 1;
  min-height: 160px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(0,0,0,0.2);
  border: 1px dashed rgba(201,164,76,0.1);
  border-radius: 0;
}

.sim-svg-small {
  width: 100%;
  height: 100%;
  max-height: 160px;
}

/* ─── Identity Layout ────────────────────────────────────── */
.sk-identity-layout { display: grid; grid-template-columns: 1fr 1fr; gap: clamp(3rem,5vw,5rem); align-items: start; }
.identity-nav-cards { display: flex; flex-direction: column; border: 1px solid var(--border); border-radius: 0; overflow: hidden; margin-top: 1rem; }
.sk-nav-card { display: flex; align-items: center; gap: 1.2rem; padding: 1.4rem 1.8rem; background: var(--panel); border-bottom: 1px solid var(--border); text-decoration: none; transition: background 250ms ease; }
.sk-nav-card:last-child { border-bottom: none; }
.sk-nav-card:hover { background: #181818; }
.sk-nav-card.back { opacity: 0.7; }
.sk-nav-card.back:hover { opacity: 1; }
.nav-card-arrow { font-size: 1.1rem; color: var(--gold); flex-shrink: 0; transition: transform 240ms ease; }
.sk-nav-card:hover:not(.back) .nav-card-arrow { transform: translateX(3px); }
.sk-nav-card.back:hover .nav-card-arrow { transform: translateX(-3px); }
.nav-card-text { display: flex; flex-direction: column; gap: 0.2rem; }
.nav-card-label { font-family: var(--font-tech); font-size: 0.6rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.1em; color: var(--text-muted); }
.nav-card-title { font-family: var(--font-tech); font-size: 0.9rem; font-weight: 600; color: var(--text); }

/* ─── Minimax Engine Simulator ────────────────────────────── */
.sk-engine-panel {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 2rem;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 0;
  overflow: hidden;
  box-shadow: 0 25px 55px rgba(0,0,0,0.5);
  margin-top: 1.5rem;
}
.engine-sidebar {
  padding: 1.8rem;
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
  background: #000000;
}
.engine-panel-title {
  font-family: var(--font-tech);
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text);
  margin: 0;
}
.engine-controls {
  display: flex;
  flex-direction: column;
  gap: 1.2rem;
}
.control-label {
  display: block;
  font-family: var(--font-tech);
  font-size: 0.68rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  margin-bottom: 0.4rem;
}
.sk-select {
  width: 100%;
  background: #181818;
  border: 1px solid var(--border);
  color: var(--text);
  padding: 0.6rem;
  font-family: var(--font-tech);
  font-size: 0.8rem;
  border-radius: 0;
  outline: none;
  transition: border-color 200ms ease;
}
.sk-select:focus {
  border-color: var(--gold);
}
.slider-wrap {
  display: flex;
  align-items: center;
  gap: 1rem;
}
.sk-slider {
  flex: 1;
  accent-color: var(--gold);
  height: 4px;
  border-radius: 2px;
  background: rgba(255,255,255,0.1);
  cursor: pointer;
}
.slider-display-val {
  font-family: var(--font-tech);
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--gold);
  min-width: 50px;
}
.engine-actions {
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
  margin-top: 0.5rem;
}
.sk-btn {
  font-family: var(--font-tech);
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  padding: 0.75rem 1rem;
  border-radius: 0;
  cursor: pointer;
  transition: all 250ms ease;
  border: 1px solid transparent;
  text-align: center;
}
.sk-btn--primary {
  background: var(--gold);
  color: #000;
}
.sk-btn--primary:hover {
  background: #e5bd5c;
  box-shadow: 0 0 15px rgba(201,164,76,0.3);
}
.sk-btn--secondary {
  background: transparent;
  border-color: var(--border);
  color: var(--text-sec);
}
.sk-btn--secondary:hover {
  border-color: var(--border-h);
  color: var(--text);
}
.engine-telemetry {
  border-top: 1px solid var(--border);
  padding-top: 1.2rem;
}
.telemetry-title {
  font-family: var(--font-tech);
  font-size: 0.68rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  margin: 0 0 0.8rem;
}
.telemetry-rows {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}
.tel-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-family: var(--font-tech);
}
.tel-lbl {
  font-size: 0.62rem;
  color: var(--text-muted);
}
.tel-val {
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--text-sec);
}

.engine-viewport {
  display: grid;
  grid-template-rows: auto 1fr auto;
  min-height: 400px;
}
.viewport-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem 1.6rem;
  background: #000000;
  border-bottom: 1px solid var(--border);
}
.viewport-title {
  font-family: var(--font-tech);
  font-size: 0.65rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  color: var(--text-sec);
}
.eval-bar-wrap {
  display: flex;
  align-items: center;
  gap: 0.6rem;
}
.eval-label {
  font-family: var(--font-tech);
  font-size: 0.6rem;
  color: var(--text-muted);
  font-weight: 700;
}
.eval-bar {
  width: 80px;
  height: 14px;
  background: #333;
  border: 1px solid rgba(255,255,255,0.1);
  border-radius: 0;
  position: relative;
  overflow: hidden;
}
.eval-fill {
  background: var(--gold);
  width: 100%;
  position: absolute;
  bottom: 0;
  left: 0;
  transition: height 600ms cubic-bezier(0.22,1,0.36,1);
}
.eval-num {
  position: absolute;
  font-family: var(--font-tech);
  font-size: 0.58rem;
  font-weight: 700;
  color: #fff;
  width: 100%;
  text-align: center;
  top: 0;
  line-height: 14px;
  mix-blend-mode: difference;
}

.tree-canvas-wrap {
  position: relative;
  background: #000000;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
}
.tree-svg {
  width: 100%;
  height: 100%;
  min-height: 320px;
}
.engine-feedback-console {
  background: #000000;
  border-top: 1px solid var(--border);
  padding: 0.8rem 1.6rem;
  font-family: var(--font-tech);
  font-size: 0.72rem;
  color: var(--text-muted);
  min-height: 45px;
  display: flex;
  align-items: center;
}
.engine-log-highlight {
  color: var(--gold);
}
.engine-log-pruned {
  color: #e74c3c;
}
.engine-log-eval {
  color: #2ecc71;
}

/* Tree node animations */
.tree-node-circle {
  fill: #141414;
  stroke: rgba(201,164,76,0.3);
  stroke-width: 1.5;
  transition: all 400ms ease;
}
.tree-node-circle.active {
  fill: rgba(201,164,76,0.2);
  stroke: var(--gold);
  filter: drop-shadow(0 0 4px var(--gold));
}
.tree-node-circle.pruned {
  fill: rgba(231,76,60,0.15);
  stroke: #e74c3c;
}
.tree-node-circle.best {
  fill: rgba(46,204,113,0.2);
  stroke: #2ecc71;
  filter: drop-shadow(0 0 4px #2ecc71);
}
.tree-text {
  font-family: var(--font-tech);
  font-size: 9px;
  fill: var(--text-sec);
  text-anchor: middle;
  pointer-events: none;
}
.tree-text-eval {
  font-family: var(--font-tech);
  font-size: 7.5px;
  fill: var(--text-muted);
  text-anchor: middle;
  pointer-events: none;
}
.tree-edge {
  stroke: rgba(255,255,255,0.06);
  stroke-width: 1.5;
  transition: all 400ms ease;
}
.tree-edge.active {
  stroke: rgba(201,164,76,0.6);
  stroke-width: 2;
}
.tree-edge.best {
  stroke: rgba(46,204,113,0.7);
  stroke-width: 2.5;
}
.tree-edge.pruned {
  stroke: rgba(231,76,60,0.3);
  stroke-dasharray: 3 3;
}

/* ─── Play Me Section ────────────────────────────────────── */
.sk-play-me-panel {
  display: flex;
  gap: 2.5rem;
  align-items: start;
  margin-top: 1.5rem;
}

.pm-board-col {
  display: flex;
  flex-direction: column;
  gap: 0.8rem;
  flex: 1.3;
  max-width: 660px;
  width: 100%;
}

.pm-conn-indicator {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.pm-engine-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  flex-shrink: 0;
  transition: background 400ms ease, box-shadow 400ms ease;
}
.pm-engine-dot.idle {
  background: #2ecc71;
  box-shadow: 0 0 6px rgba(46,204,113,0.45);
}
.pm-engine-dot.thinking {
  background: var(--gold);
  box-shadow: 0 0 8px rgba(201,164,76,0.6);
  animation: pmDotPulse 0.7s infinite alternate;
}
.pm-engine-dot.error { background: #e74c3c; }

@keyframes pmDotPulse {
  0%   { opacity: 0.55; transform: scale(0.85); }
  100% { opacity: 1;    transform: scale(1.2); box-shadow: 0 0 14px var(--gold); }
}

.pm-engine-text {
  font-family: var(--font-tech);
  font-size: 0.62rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
}

/* Last-move highlight on play board */
.chess-cell.pm-last-move {
  background: rgba(201,164,76,0.25) !important;
  box-shadow: inset 0 0 8px rgba(201,164,76,0.3);
}

/* Side Panel */
.pm-side-panel {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  position: sticky;
  top: 80px;
  flex: 1;
  min-width: 280px;
  max-width: 440px;
}

/* Difficulty Modes */
.pm-modes-section {
  background: #000000;
  border: 1px solid var(--border);
  border-radius: 0;
  padding: 1rem 1.1rem;
}

.pm-modes-label {
  font-family: var(--font-tech);
  font-size: 0.58rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-muted);
  margin-bottom: 0.7rem;
  padding-bottom: 0.55rem;
  border-bottom: 1px solid var(--border);
}

.pm-modes-list {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
}

.pm-mode-btn {
  display: grid;
  grid-template-columns: 48px 1fr auto;
  align-items: center;
  gap: 0.6rem;
  width: 100%;
  background: transparent;
  border: 1px solid transparent;
  border-radius: 0;
  padding: 0.5rem 0.65rem;
  cursor: pointer;
  text-align: left;
  transition: all 180ms ease;
}

.pm-mode-btn:hover {
  background: rgba(255,255,255,0.03);
  border-color: var(--border);
}

.pm-mode-btn.active {
  background: rgba(201,164,76,0.07);
  border-color: rgba(201,164,76,0.3);
}

.pm-mode-btn--me.active {
  background: rgba(201,164,76,0.1);
  border-color: rgba(201,164,76,0.45);
  box-shadow: 0 0 12px rgba(201,164,76,0.08);
}

.pm-mode-age {
  font-family: var(--font-tech);
  font-size: 0.62rem;
  font-weight: 700;
  color: var(--text-muted);
  white-space: nowrap;
}

.pm-mode-btn.active .pm-mode-age,
.pm-mode-btn--me.active .pm-mode-age {
  color: var(--gold);
}

.pm-mode-name {
  font-family: var(--font-tech);
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--text-sec);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.pm-mode-btn.active .pm-mode-name { color: var(--text); }

.pm-mode-meta {
  font-family: var(--font-tech);
  font-size: 0.55rem;
  color: var(--text-muted);
  white-space: nowrap;
}

.pm-mode-btn.active .pm-mode-meta { color: rgba(201,164,76,0.7); }

.pm-modes-divider {
  font-family: var(--font-tech);
  font-size: 0.55rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--text-muted);
  padding: 0.4rem 0.2rem 0.1rem;
  border-top: 1px dashed rgba(255,255,255,0.07);
  margin-top: 0.15rem;
  opacity: 0.6;
}

.pm-mode-btn--future .pm-mode-age { color: rgba(120,180,255,0.7); }
.pm-mode-btn--future .pm-mode-name { color: rgba(180,200,255,0.55); }
.pm-mode-btn--future .pm-mode-meta { color: rgba(120,180,255,0.4); }
.pm-mode-btn--future:hover .pm-mode-name { color: rgba(180,200,255,0.85); }
.pm-mode-btn--future.active .pm-mode-age  { color: rgba(140,190,255,0.9); }
.pm-mode-btn--future.active .pm-mode-name { color: rgba(200,220,255,0.9); }
.pm-mode-btn--future.active {
  background: rgba(100,150,255,0.06);
  border-color: rgba(100,150,255,0.25);
}

/* Eval bar */
.pm-eval-section {
  background: #000000;
  border: 1px solid var(--border);
  border-radius: 0;
  padding: 1.1rem 1.2rem;
}

.pm-eval-label {
  font-family: var(--font-tech);
  font-size: 0.58rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-muted);
  margin-bottom: 0.75rem;
}

.pm-eval-bar-wrap {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.5rem;
}

.pm-eval-side-label {
  font-family: var(--font-tech);
  font-size: 0.62rem;
  font-weight: 700;
  color: var(--text);
  min-width: 12px;
}
.pm-eval-side-label--b { color: var(--text-muted); }

.pm-eval-bar {
  flex: 1;
  height: 18px;
  background: #333;
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: 0;
  position: relative;
  overflow: hidden;
}

.pm-eval-fill {
  height: 100%;
  background: linear-gradient(90deg, #f0ede4, #d8d0be);
  transition: width 600ms cubic-bezier(0.22,1,0.36,1);
  position: absolute;
  left: 0; top: 0;
}

.pm-eval-num {
  position: absolute;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
  font-family: var(--font-tech);
  font-size: 0.65rem;
  font-weight: 700;
  color: #fff;
  mix-blend-mode: difference;
  pointer-events: none;
  white-space: nowrap;
}

.pm-eval-desc {
  font-family: var(--font-tech);
  font-size: 0.65rem;
  color: var(--text-muted);
}

/* Engine best line */
.pm-engine-line-box {
  background: #000000;
  border: 1px solid var(--border);
  border-left: 2px solid var(--gold);
  border-radius: 0;
  padding: 0.9rem 1.1rem;
}

.pm-engine-line-label {
  font-family: var(--font-tech);
  font-size: 0.58rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-muted);
  margin-bottom: 0.4rem;
}

.pm-engine-line-moves {
  font-family: var(--font-tech);
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--gold);
  letter-spacing: 0.05em;
  word-break: break-word;
  min-height: 1.2em;
}

.pm-line-hidden { display: none; }

.pm-engine-line-reveal { display: flex; }

.pm-reveal-btn {
  font-family: var(--font-tech);
  font-size: 0.65rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  background: transparent;
  border: 1px dashed rgba(201,164,76,0.35);
  color: var(--text-muted);
  padding: 0.45rem 0.9rem;
  border-radius: 0;
  cursor: pointer;
  transition: all 220ms ease;
  width: 100%;
}
.pm-reveal-btn:hover {
  border-color: var(--gold);
  color: var(--gold);
  background: rgba(201,164,76,0.05);
}

/* Move history */
.pm-move-section {
  background: #000000;
  border: 1px solid var(--border);
  border-radius: 0;
  padding: 1rem 1.1rem;
}

.pm-move-title {
  font-family: var(--font-tech);
  font-size: 0.58rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-muted);
  margin-bottom: 0.7rem;
  padding-bottom: 0.55rem;
  border-bottom: 1px solid var(--border);
}

.pm-move-list {
  max-height: 150px;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
  scrollbar-width: thin;
  scrollbar-color: rgba(201,164,76,0.18) transparent;
}

.pm-move-row {
  display: grid;
  grid-template-columns: 24px 1fr 1fr;
  gap: 0.4rem;
  align-items: center;
  padding: 0.2rem 0.3rem;
  border-radius: 0;
  transition: background 120ms ease;
}
.pm-move-row:hover { background: rgba(255,255,255,0.03); }

.pm-move-num {
  font-family: var(--font-tech);
  font-size: 0.62rem;
  color: var(--text-muted);
}

.pm-move-white, .pm-move-black {
  font-family: var(--font-tech);
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-sec);
}

/* Controls */
.pm-controls {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.6rem;
}

/* Engine footer */
.pm-engine-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.7rem 1rem;
  background: #000000;
  border: 1px solid var(--border);
  border-radius: 0;
}

.pm-engine-badge {
  font-family: var(--font-tech);
  font-size: 0.6rem;
  font-weight: 700;
  color: var(--gold);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.pm-engine-specs {
  font-family: var(--font-tech);
  font-size: 0.56rem;
  color: var(--text-muted);
  letter-spacing: 0.03em;
}

/* ─── Lessons Layout (Thinking Under Consequence) ────────── */
.sk-lessons-layout {
  display: grid;
  grid-template-columns: 1fr 1.35fr;
  gap: 3rem;
  margin-top: 1.5rem;
  align-items: start;
}

.sk-lessons-showcase {
  position: sticky;
  top: 100px;
}

.showcase-frame {
  position: relative;
  border: 1px solid var(--border);
  border-radius: 0;
  overflow: hidden;
  aspect-ratio: 4 / 5;
  background: #000;
  box-shadow: 0 20px 50px rgba(0, 0, 0, 0.4);
}

.showcase-img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  opacity: 0.82;
  transition: transform 800ms cubic-bezier(0.25, 1, 0.5, 1),
              opacity 500ms ease;
}

.showcase-frame:hover .showcase-img {
  transform: scale(1.05);
  opacity: 0.95;
}

/* Corner Brackets */
.frame-bracket {
  position: absolute;
  width: 12px;
  height: 12px;
  border: 2px solid var(--gold);
  z-index: 5;
  pointer-events: none;
  opacity: 0.6;
  transition: opacity 300ms ease, border-color 300ms ease;
}

.showcase-frame:hover .frame-bracket {
  opacity: 1;
}

.frame-bracket.tl { top: 12px; left: 12px; border-right: none; border-bottom: none; }
.frame-bracket.tr { top: 12px; right: 12px; border-left: none; border-bottom: none; }
.frame-bracket.bl { bottom: 12px; left: 12px; border-right: none; border-top: none; }
.frame-bracket.br { bottom: 12px; right: 12px; border-left: none; border-top: none; }

/* Status Badge */
.showcase-status-badge {
  position: absolute;
  top: 20px;
  left: 20px;
  background: rgba(13, 13, 13, 0.75);
  backdrop-filter: blur(8px);
  border: 1px solid var(--border);
  border-radius: 0;
  padding: 0.4rem 0.75rem;
  font-family: var(--font-tech);
  font-size: 0.62rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  color: var(--text-sec);
  display: flex;
  align-items: center;
  gap: 0.5rem;
  z-index: 4;
}

.status-pulse-dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: #2ecc71;
  box-shadow: 0 0 8px #2ecc71;
  animation: hudPulse 1.5s infinite alternate;
}

@keyframes hudPulse {
  0% { opacity: 0.4; }
  100% { opacity: 1; }
}

/* HUD overlay */
.showcase-hud {
  position: absolute;
  bottom: 20px;
  left: 20px;
  right: 20px;
  background: rgba(5, 5, 5, 0.8);
  backdrop-filter: blur(10px);
  border: 1px solid var(--border);
  border-radius: 0;
  padding: 0.9rem 1.2rem;
  display: flex;
  align-items: center;
  gap: 1.2rem;
  z-index: 4;
}

.hud-eval {
  font-family: var(--font-tech);
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--gold);
  border-right: 1px solid var(--border);
  padding-right: 1.2rem;
  text-shadow: 0 0 10px rgba(201, 164, 76, 0.2);
}

.hud-details {
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
}

.hud-lbl {
  font-family: var(--font-tech);
  font-size: 0.58rem;
  color: var(--text-muted);
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

.hud-val {
  font-family: var(--font-tech);
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--text-sec);
}

/* ─── Responsive ─────────────────────────────────────────── */
@media (max-width: 980px) {
  .sk-hero-grid { grid-template-columns: 1fr; }
  .sk-lessons-layout { grid-template-columns: 1fr; gap: 2rem; }
  .sk-lessons-showcase { position: static; }
  .showcase-frame { aspect-ratio: 16 / 10; }
  .sk-lesson-cards { grid-template-columns: 1fr; }
  .sk-identity-layout { grid-template-columns: 1fr; }
  .sk-chess-profile-grid { grid-template-columns: 1fr; gap: 1.5rem; }
  .profile-stats-grid { grid-template-columns: 1fr; }
  .sk-engine-panel { grid-template-columns: 1fr; }
  .engine-sidebar { border-right: none; border-bottom: 1px solid var(--border); }
  .sim-content-wrapper { grid-template-columns: 1fr; }
  .sim-controls { border-right: none; border-bottom: 1px solid var(--border); }
  .sim-metrics { margin-top: 1.5rem; }
  .sk-play-me-panel { flex-direction: column; }
  .pm-board-col { max-width: 100%; }
  .pm-side-panel { position: static; max-width: 100%; }
}