/* ============================================================
   神经网络游乐场
   ============================================================ */

.playground-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}
.playground-head h3 { margin: 0 0 2px; }

.pg-counter {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  padding: 5px 6px;
  border-radius: 999px;
  background: var(--blue-soft);
  border: 1px solid #dbe3ff;
}
.pg-num-btn {
  width: 36px;
  height: 36px;
  display: grid;
  place-items: center;
  border: 0;
  border-radius: 50%;
  background: var(--blue);
  color: #fff;
  font-size: 20px;
  font-weight: 800;
  line-height: 1;
  cursor: pointer;
  transition: background 0.15s ease, transform 0.15s ease;
}
.pg-num-btn:hover { background: var(--blue-deep); }
.pg-num-btn:active { transform: scale(0.92); }
.pg-num-btn:focus-visible { outline: 3px solid #b9ccff; outline-offset: 2px; }
.pg-counter .val {
  min-width: 34px;
  text-align: center;
  font-size: 21px;
  font-weight: 900;
  font-variant-numeric: tabular-nums;
}

.layer-chips {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(148px, 1fr));
  gap: 12px;
  margin-top: 18px;
}
.pg-layer-chip {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 7px;
  padding: 13px 10px 11px;
  border-radius: 16px;
  background: #fff8e8;
  border: 1.5px dashed #f0cf8e;
}
.pg-layer-chip--input { background: var(--green-soft); border-color: #9fd9bd; }
.pg-layer-chip--output { background: var(--orange-soft); border-color: #f9d7ba; }
.pg-layer-chip__name { font-size: 14px; font-weight: 900; }
.pg-layer-chip__hint { font-size: 12px; font-weight: 700; color: var(--faint); }
.pg-layer-chip .pg-counter {
  padding: 3px 4px;
  background: #fff;
  border-color: var(--line);
}
.pg-layer-chip .pg-num-btn { width: 28px; height: 28px; font-size: 16px; }
.pg-layer-chip .pg-counter .val { min-width: 26px; font-size: 16px; }

.playground-toolbar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
}
.playground-switches {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 22px;
  margin-top: 15px;
  padding-top: 15px;
  border-top: 1px dashed var(--line);
}
.pg-check {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 14.5px;
  font-weight: 700;
  color: var(--ink-2);
  cursor: pointer;
}
.pg-check input { width: 18px; height: 18px; accent-color: var(--blue); }

.playground-legend {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px 20px;
  font-size: 13.5px;
  font-weight: 600;
  color: var(--muted);
}
.pg-swatch { display: inline-flex; align-items: center; gap: 7px; }
.pg-swatch::before {
  content: "";
  width: 30px;
  height: 4px;
  border-radius: 2px;
  background: var(--blue);
}
.pg-swatch--neg::before { background: var(--orange); }
.pg-swatch--thick::before { height: 7px; }

.net-scroll {
  margin-top: 12px;
  padding: 8px 6px;
  overflow-x: auto;
  overscroll-behavior-x: contain;
  border: 1px solid #e7ebf7;
  border-radius: 16px;
  background: linear-gradient(180deg, #fbfcff, #f7f9ff);
  -webkit-overflow-scrolling: touch;
}
.net-scroll svg { display: block; margin: 0 auto; }
.pg-hint-mobile { display: none; }

.pg-svg .pg-edge { transition: opacity 0.2s ease, stroke-width 0.2s ease; }
.pg-svg .pg-edge.is-dim { opacity: 0.1; }
.pg-edge-label {
  font-family: var(--mono);
  font-size: 11.5px;
  font-weight: 700;
  fill: #5f6680;
  paint-order: stroke;
  stroke: #fff;
  stroke-width: 3.5px;
  stroke-linejoin: round;
  pointer-events: none;
}
.pg-edge-label.is-dim { opacity: 0.1; }
.pg-neuron { cursor: pointer; }
.pg-neuron:focus-visible { outline: none; }
.pg-neuron circle { transition: stroke-width 0.2s ease, filter 0.2s ease; }
.pg-neuron:hover circle,
.pg-neuron:focus-visible circle { stroke-width: 5; }
.pg-neuron.is-active circle {
  stroke-width: 5;
  filter: drop-shadow(0 4px 8px rgba(59, 110, 246, 0.28));
}
.pg-neuron text {
  font-size: 15px;
  font-weight: 800;
  text-anchor: middle;
  dominant-baseline: central;
  pointer-events: none;
  fill: var(--ink);
}
.pg-layer-title {
  font-size: 13.5px;
  font-weight: 900;
  letter-spacing: 0.04em;
  text-anchor: middle;
  fill: var(--faint);
}
.pg-input {
  width: 60px;
  height: 34px;
  padding: 0;
  border: 2px solid var(--green);
  border-radius: 10px;
  background: #f3fffb;
  color: var(--ink);
  font: inherit;
  font-size: 16px;
  font-weight: 800;
  text-align: center;
}
.pg-input:focus { outline: 3px solid #b9e8d3; outline-offset: 1px; }

.pg-explain-card { background: linear-gradient(180deg, #fff, #fbfcff); }
.pg-explain-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  flex-wrap: wrap;
  margin-bottom: 10px;
}
.pg-explain { min-height: 92px; font-size: 16px; line-height: 1.8; }
.pg-explain .pg-formula {
  display: block;
  margin-top: 8px;
  padding: 10px 14px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: #f4f6fc;
  font-family: var(--mono);
  font-size: 14px;
  line-height: 1.9;
  overflow-wrap: anywhere;
}
.pg-explain .pg-formula b { color: var(--blue-deep); }

@media (max-width: 700px) {
  .pg-hint-mobile.is-visible { display: block; }
  .layer-chips { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 9px; }
  .pg-layer-chip { padding: 11px 6px 9px; }
  .pg-layer-chip__name { font-size: 13px; }
  .playground-switches { gap: 10px 16px; }
  .pg-explain { font-size: 15px; }
}