/* Explainer videos: a "Watch" button in each topic head that drops down an inline player. */
.topic-head { flex-wrap: wrap; }
.vbtn {
  margin-left: auto; align-self: center;
  display: inline-flex; align-items: center; gap: 8px;
  font: 600 0.8rem/1 var(--sans); letter-spacing: 0.02em;
  color: var(--ion); background: rgba(94,211,244,0.08);
  border: 1px solid rgba(94,211,244,0.35); border-radius: 999px;
  padding: 7px 12px 7px 9px; cursor: pointer;
  transition: background .15s, border-color .15s, color .15s;
}
.vbtn:hover { background: rgba(94,211,244,0.16); border-color: var(--ion); }
.vbtn:focus-visible { outline: 2px solid var(--ion); outline-offset: 2px; }
.vbtn .vplay { width: 20px; height: 20px; border-radius: 50%; background: var(--ion); display: grid; place-items: center; flex-shrink: 0; }
.vbtn .vplay svg { width: 9px; height: 9px; margin-left: 2px; fill: var(--void); }
.vbtn .vdur { font-family: var(--mono); font-weight: 500; color: var(--text-dim); font-size: 0.74rem; }
.vbtn .vchev { width: 12px; height: 12px; stroke: currentColor; fill: none; stroke-width: 2.4; transition: transform .2s; }
.vbtn[aria-expanded="true"] { background: var(--ion); color: var(--void); border-color: var(--ion); }
.vbtn[aria-expanded="true"] .vplay { background: var(--void); }
.vbtn[aria-expanded="true"] .vplay svg { fill: var(--ion); }
.vbtn[aria-expanded="true"] .vdur { color: var(--deep); }
.vbtn[aria-expanded="true"] .vchev { transform: rotate(180deg); }

.vpanel { display: grid; grid-template-rows: 0fr; transition: grid-template-rows .3s ease, margin .3s ease; margin: 0; }
.vpanel.open { grid-template-rows: 1fr; margin: -6px 0 22px; }
.vpanel > .vinner { overflow: hidden; min-height: 0; }
.vframe {
  background: var(--deep); border: 1px solid var(--line); border-radius: 12px; overflow: hidden;
  box-shadow: 0 14px 40px rgba(0,0,0,0.35);
}
.vframe video { display: block; width: 100%; aspect-ratio: 16 / 9; background: #000; }
.vbar {
  display: flex; flex-wrap: wrap; align-items: center; gap: 6px;
  padding: 9px 12px; border-top: 1px solid var(--line);
  font: 0.74rem/1.3 var(--mono); color: var(--text-dim);
}
.vbar .vlabel { margin-right: auto; letter-spacing: 0.04em; }
.vbar button {
  font: 600 0.72rem/1 var(--mono); color: var(--text-dim); background: transparent;
  border: 1px solid var(--line); border-radius: 6px; padding: 5px 8px; cursor: pointer;
}
.vbar button:hover { color: var(--text); border-color: var(--text-dim); }
.vbar button.on { color: var(--void); background: var(--ion); border-color: var(--ion); }
.toc-row .vdot { margin-left: 6px; font-size: 0.6rem; color: var(--ion); opacity: 0.75; vertical-align: 1px; }
#vcount { font-family: var(--mono); }
@media (max-width: 640px) {
  .vbtn { margin-left: 0; margin-top: 4px; }
  .vbar .vlabel { width: 100%; }
}
/* touch screens: tap targets of at least ~40px */
@media (pointer: coarse) {
  .vbar { gap: 8px; }
  .vbar button { min-height: 40px; min-width: 44px; padding: 8px 12px; }
  .vbtn { min-height: 40px; }
  .gt-play { min-width: 40px; min-height: 40px; }
}
@media (prefers-reduced-motion: reduce) { .vpanel, .vbtn .vchev { transition: none; } }
/* glossary */
.gl-vrow { display: flex; flex-wrap: wrap; gap: 8px; margin: 4px 0 14px; }
.gl-vrow .vbtn { margin-left: 0; }
.gterm .vpanel, .gcat .vpanel { grid-column: 1 / -1; margin-top: 10px; }
.gt-play {
  margin-left: 8px; display: inline-flex; align-items: center; gap: 4px; vertical-align: 1px;
  font: 600 0.68rem/1 var(--mono); color: var(--ion); background: rgba(94,211,244,0.08);
  border: 1px solid rgba(94,211,244,0.3); border-radius: 999px; padding: 3px 7px 3px 6px; cursor: pointer;
}
.gt-play svg { width: 8px; height: 8px; fill: var(--ion); }
.gt-play:hover { background: rgba(94,211,244,0.18); }