/* ============================================================
   panels.css — the interactive panels that are not the table itself.

   One block per section, in section order, so that finding the styles
   for a panel means scrolling to where that panel appears in the lesson.
   ============================================================ */

/* ============================================================
   §01 — Mendeleev's cards
   ============================================================ */

.cards-strip {
  display: grid;
  gap: var(--s-2);
  overflow-x: auto;
  padding-bottom: var(--s-2);
}

.cards-strip__row {
  display: grid;
  gap: 4px;
  grid-auto-flow: column;
  justify-content: start;
}

.mcard {
  --mc: var(--ink-3);
  width: 84px;
  display: grid;
  gap: 1px;
  padding: 7px 6px;
  border-radius: var(--r-sm);
  border: 1px solid color-mix(in srgb, var(--mc) 45%, transparent);
  background: color-mix(in srgb, var(--mc) 13%, transparent);
  text-align: center;
  transition: all var(--dur) var(--ease);
}

.mcard b {
  font-size: var(--t-md);
  font-weight: 700;
  line-height: 1.05;
}

.mcard span {
  font-size: 10px;
  color: var(--ink-3);
  font-variant-numeric: tabular-nums;
  line-height: 1.25;
}

/* Same fitting trick as the table cells: the character count comes in as
   --nlen and the font size divides by it, so "Tin" and "Phosphorus" both
   sit on one line inside the same 84px card.

   Written as a descendant selector rather than a bare class because
   `.mcard span` above already sets a colour and a size, and losing to it
   would be silent. Two classes beat one class plus an element. */
.mcard .mcard__name {
  font-size: max(7px, min(11px, calc(84px * 1.5 / var(--nlen, 8))));
  color: var(--ink-2);
  font-weight: 600;
  line-height: 1.2;
  overflow: hidden;
  white-space: nowrap;
}

.swapcard .swapcard__name {
  font-size: var(--t-sm);
  font-weight: 600;
  color: var(--ink-2);
}

.mcard.is-lit {
  --mc: var(--accent);
  box-shadow: 0 0 0 2px color-mix(in srgb, var(--accent) 55%, transparent);
}

.mcard.is-gap {
  border-style: dashed;
  background: transparent;
  color: var(--ink-3);
}

.mcard.is-gap b {
  color: var(--warn);
}

/* The column that lines up when the wrap length is right. */
.mcard.is-family {
  --mc: var(--ok);
}

.wrapverdict {
  display: grid;
  gap: var(--s-2);
  margin-top: var(--s-4);
  padding: var(--s-4) var(--s-5);
  border-radius: var(--r-md);
  border: 1px solid var(--line);
  background: var(--surface);
  border-left: 3px solid var(--ink-3);
}

.wrapverdict.is-right {
  border-left-color: var(--ok);
  background: color-mix(in srgb, var(--ok) 9%, transparent);
}

/* ============================================================
   §02 — mass order against proton order
   ============================================================ */

.swaprow {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(90px, 1fr));
  gap: var(--s-2);
  margin-top: var(--s-3);
}

.swapcard {
  display: grid;
  gap: 2px;
  padding: 10px;
  border-radius: var(--r-sm);
  border: 1px solid var(--line);
  background: var(--surface-2);
  text-align: center;
  transition: all 400ms var(--ease);
}

.swapcard b {
  font-size: var(--t-lg);
}

.swapcard span {
  font-size: var(--t-xs);
  color: var(--ink-3);
  font-variant-numeric: tabular-nums;
}

.swapcard.is-wrongway {
  border-color: var(--bad);
  background: color-mix(in srgb, var(--bad) 12%, transparent);
}

.swapcard.is-fixed {
  border-color: var(--ok);
  background: color-mix(in srgb, var(--ok) 12%, transparent);
}

/* ============================================================
   §03 / §04 — the filling order ladder
   ============================================================ */

.ladder {
  display: grid;
  gap: 3px;
  font-family: var(--mono);
}

.ladder__row {
  display: grid;
  grid-template-columns: 30px 1fr;
  align-items: center;
  gap: var(--s-3);
}

.ladder__n {
  font-size: var(--t-sm);
  color: var(--ink-3);
  text-align: right;
}

.ladder__subs {
  display: flex;
  gap: 4px;
}

.rung {
  --rc: var(--ink-3);
  min-width: 46px;
  padding: 5px 8px;
  border-radius: var(--r-sm);
  border: 1px solid color-mix(in srgb, var(--rc) 40%, transparent);
  background: color-mix(in srgb, var(--rc) 12%, transparent);
  font-size: var(--t-sm);
  text-align: center;
  color: var(--ink-2);
  transition: all var(--dur) var(--ease);
}

.rung[data-l="s"] { --rc: var(--blk-s); }
.rung[data-l="p"] { --rc: var(--blk-p); }
.rung[data-l="d"] { --rc: var(--blk-d); }
.rung[data-l="f"] { --rc: var(--blk-f); }

.rung.is-full {
  background: color-mix(in srgb, var(--rc) 34%, transparent);
  color: var(--ink);
  font-weight: 700;
}

.rung.is-filling {
  border-color: var(--ink);
  box-shadow: 0 0 0 2px color-mix(in srgb, var(--accent) 45%, transparent);
  color: var(--ink);
  font-weight: 700;
}

.rung.is-empty {
  opacity: 0.34;
}

/* The diagonal-rule arrows drawn over the ladder. */
.ladder-wrap {
  position: relative;
}

.ladder-wrap svg {
  position: absolute;
  inset: 0;
  pointer-events: none;
  overflow: visible;
}

.ordertrack {
  display: flex;
  flex-wrap: wrap;
  gap: 4px;
  font-family: var(--mono);
  font-size: var(--t-sm);
  margin-top: var(--s-3);
}

/* ============================================================
   §04 — the Aufbau machine
   ============================================================ */

.aufbar {
  display: flex;
  align-items: center;
  gap: var(--s-3);
  flex-wrap: wrap;
  margin-bottom: var(--s-4);
}

.aufbar__z {
  font-family: var(--mono);
  font-size: var(--t-2xl);
  font-weight: 700;
  min-width: 3ch;
  text-align: right;
  font-variant-numeric: tabular-nums;
}

.ecount {
  display: flex;
  gap: 3px;
  flex-wrap: wrap;
  max-width: 100%;
}

.epip {
  width: 9px;
  height: 9px;
  border-radius: 50%;
  background: var(--electron);
  opacity: 0.9;
}

.epip.is-spare {
  background: var(--line-strong);
}

/* ============================================================
   §05 — the blocks
   ============================================================ */

.blockmath {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(190px, 1fr));
  gap: var(--s-3);
}

.blockmath__item {
  --bc: var(--ink-3);
  padding: var(--s-4);
  border-radius: var(--r-md);
  border: 1px solid color-mix(in srgb, var(--bc) 40%, transparent);
  background: color-mix(in srgb, var(--bc) 10%, transparent);
}

.blockmath__item[data-blk="s"] { --bc: var(--blk-s); }
.blockmath__item[data-blk="p"] { --bc: var(--blk-p); }
.blockmath__item[data-blk="d"] { --bc: var(--blk-d); }
.blockmath__item[data-blk="f"] { --bc: var(--blk-f); }

.blockmath__item h4 {
  margin-bottom: 4px;
}

.blockmath__eq {
  font-family: var(--mono);
  font-size: var(--t-md);
  color: var(--ink);
  margin-bottom: 4px;
}

.blockmath__item p {
  font-size: var(--t-xs);
  color: var(--ink-3);
  margin: 0;
}

/* ============================================================
   §08 — the tug of war
   ============================================================ */

.tug {
  display: grid;
  gap: var(--s-4);
  padding: var(--s-5);
  border-radius: var(--r-lg);
  border: 1px solid var(--line);
  background: var(--surface-2);
}

.tug__scene {
  position: relative;
  height: 172px;
  border-radius: var(--r-md);
  background: var(--plane-bg);
  border: 1px solid var(--line);
  overflow: hidden;
}

.tug__nucleus {
  position: absolute;
  left: 46px;
  top: 50%;
  transform: translate(-50%, -50%);
  width: 54px;
  height: 54px;
  border-radius: 50%;
  display: grid;
  place-items: center;
  background: radial-gradient(circle at 34% 30%, #fff6, transparent 60%), var(--nucleus);
  color: #fff;
  font-weight: 700;
  font-size: var(--t-sm);
  box-shadow: 0 0 26px color-mix(in srgb, var(--nucleus) 55%, transparent);
  transition: all 420ms var(--ease);
}

.tug__shellring {
  position: absolute;
  left: 46px;
  top: 50%;
  transform: translate(-50%, -50%);
  border-radius: 50%;
  border: 1px dashed var(--shell);
  transition: all 420ms var(--ease);
}

.tug__electron {
  position: absolute;
  top: 50%;
  width: 16px;
  height: 16px;
  margin-top: -8px;
  margin-left: -8px;
  border-radius: 50%;
  background: var(--electron);
  box-shadow: 0 0 16px color-mix(in srgb, var(--electron) 70%, transparent);
  transition: left 420ms var(--ease);
  z-index: 2;
}

.tug__arrow {
  position: absolute;
  height: 3px;
  border-radius: 2px;
  top: 50%;
  transition: all 420ms var(--ease);
}

.tug__arrow--pull {
  background: var(--pull);
  margin-top: -14px;
}

.tug__arrow--shield {
  background: var(--shieldc);
  margin-top: 10px;
}

.tug__tag {
  position: absolute;
  font-size: var(--t-xs);
  color: var(--ink-2);
  white-space: nowrap;
}

.zeffmath {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--s-3);
  flex-wrap: wrap;
  font-family: var(--mono);
  font-size: var(--t-lg);
}

.zeffmath i {
  font-style: normal;
  color: var(--ink-3);
}

.zeffmath b[data-role="z"] { color: var(--pull); }
.zeffmath b[data-role="s"] { color: var(--shieldc); }
.zeffmath b[data-role="zeff"] { color: var(--accent-2); }

/* ============================================================
   §09 — the trend maps
   ============================================================ */

.trendhead {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--s-3);
  flex-wrap: wrap;
  margin-bottom: var(--s-3);
}

.arrowpair {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: var(--s-3);
  margin-top: var(--s-4);
}

.arrowcard {
  padding: var(--s-4);
  border-radius: var(--r-md);
  border: 1px solid var(--line);
  background: var(--surface);
}

.arrowcard h4 {
  display: flex;
  align-items: center;
  gap: var(--s-2);
  font-size: var(--t-sm);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-3);
  margin-bottom: var(--s-2);
}

.arrowcard h4 em {
  font-style: normal;
  font-size: var(--t-md);
  color: var(--accent-2);
  letter-spacing: 0;
  text-transform: none;
}

.arrowcard p {
  font-size: var(--t-sm);
  margin: 0;
}

/* Two elements picked off the map, side by side. */
.compare {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: stretch;
  gap: var(--s-3);
  margin-top: var(--s-4);
}

.compare__slot {
  display: grid;
  gap: 4px;
  place-items: center;
  padding: var(--s-4);
  border-radius: var(--r-md);
  border: 1px dashed var(--line-strong);
  background: var(--surface);
  min-height: 96px;
  text-align: center;
}

.compare__slot.is-filled {
  border-style: solid;
}

.compare__slot b {
  font-size: var(--t-xl);
}

.compare__slot span {
  font-size: var(--t-xs);
  color: var(--ink-3);
}

.compare__vs {
  display: grid;
  place-items: center;
  font-size: var(--t-sm);
  color: var(--ink-3);
  font-weight: 700;
}

@media (max-width: 560px) {
  .compare {
    grid-template-columns: 1fr;
  }
}

/* ============================================================
   §10 — the ionisation staircase
   ============================================================ */

.stair {
  display: grid;
  grid-auto-flow: column;
  grid-auto-columns: minmax(0, 1fr);
  align-items: end;
  gap: 5px;
  height: 240px;
  padding: var(--s-3) 0 0;
  border-bottom: 1px solid var(--line-strong);
}

.stairbar {
  display: grid;
  align-content: end;
  justify-items: center;
  gap: 4px;
  height: 100%;
  position: relative;
}

.stairbar__fill {
  width: 100%;
  border-radius: 4px 4px 0 0;
  background: color-mix(in srgb, var(--accent-2) 55%, transparent);
  border: 1px solid color-mix(in srgb, var(--accent-2) 70%, transparent);
  border-bottom: 0;
  transition: height 420ms var(--ease);
  min-height: 3px;
}

.stairbar.is-core .stairbar__fill {
  background: color-mix(in srgb, var(--bad) 45%, transparent);
  border-color: color-mix(in srgb, var(--bad) 70%, transparent);
}

.stairbar.is-jump::before {
  content: "";
  position: absolute;
  left: -4px;
  top: 0;
  bottom: 0;
  border-left: 2px dashed var(--warn);
}

.stairbar__val {
  font-size: 10px;
  color: var(--ink-3);
  font-variant-numeric: tabular-nums;
  writing-mode: vertical-rl;
  transform: rotate(180deg);
  max-height: 62px;
}

.stairfoot {
  display: grid;
  grid-auto-flow: column;
  grid-auto-columns: minmax(0, 1fr);
  gap: 5px;
  margin-top: 6px;
  text-align: center;
  font-size: var(--t-xs);
  color: var(--ink-3);
}

.stairfoot span.is-jump {
  color: var(--warn);
  font-weight: 700;
}

/* ============================================================
   §11 — the families
   ============================================================ */

.famgrid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: var(--s-2);
  margin-bottom: var(--s-4);
}

.fambtn {
  --fc: var(--ink-3);
  display: grid;
  gap: 2px;
  text-align: left;
  padding: 11px 14px;
  border-radius: var(--r-md);
  border: 1px solid color-mix(in srgb, var(--fc) 40%, transparent);
  background: color-mix(in srgb, var(--fc) 9%, transparent);
  color: var(--ink-2);
  font: inherit;
  cursor: pointer;
  transition: all var(--dur) var(--ease);
}

.fambtn b {
  color: var(--ink);
  font-size: var(--t-sm);
}

.fambtn span {
  font-size: var(--t-xs);
  color: var(--ink-3);
}

.fambtn:hover {
  border-color: color-mix(in srgb, var(--fc) 75%, transparent);
}

.fambtn.is-on {
  background: color-mix(in srgb, var(--fc) 24%, transparent);
  border-color: var(--fc);
}

.fambtn[data-cat="alkali"] { --fc: var(--cat-alkali); }
.fambtn[data-cat="alkaline"] { --fc: var(--cat-alkaline); }
.fambtn[data-cat="transition"] { --fc: var(--cat-transition); }
.fambtn[data-cat="post"] { --fc: var(--cat-post); }
.fambtn[data-cat="metalloid"] { --fc: var(--cat-metalloid); }
.fambtn[data-cat="nonmetal"] { --fc: var(--cat-nonmetal); }
.fambtn[data-cat="halogen"] { --fc: var(--cat-halogen); }
.fambtn[data-cat="noble"] { --fc: var(--cat-noble); }
.fambtn[data-cat="lanthanide"] { --fc: var(--cat-lanthanide); }
.fambtn[data-cat="actinide"] { --fc: var(--cat-actinide); }

.famfacts {
  display: grid;
  gap: var(--s-2);
  margin: var(--s-3) 0 0;
  padding: 0;
  list-style: none;
}

.famfacts li {
  display: grid;
  grid-template-columns: 18px 1fr;
  gap: var(--s-2);
  font-size: var(--t-sm);
  color: var(--ink-2);
}

.famfacts li::before {
  content: "▸";
  color: var(--accent-2);
}

/* ============================================================
   §12 — ions
   ============================================================ */

.ionrow {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: var(--s-3);
  padding: var(--s-3) var(--s-4);
  border-radius: var(--r-md);
  border: 1px solid var(--line);
  background: var(--surface);
}

.ionrow__arrow {
  font-size: var(--t-lg);
  color: var(--ink-3);
}

.isoline {
  display: flex;
  align-items: flex-end;
  gap: var(--s-2);
  flex-wrap: wrap;
  margin-top: var(--s-3);
}

.isoball {
  display: grid;
  gap: 4px;
  justify-items: center;
}

.isoball__dot {
  border-radius: 50%;
  background: color-mix(in srgb, var(--accent) 30%, transparent);
  border: 1px solid var(--accent);
  transition: all 420ms var(--ease);
}

.isoball b {
  font-size: var(--t-sm);
  font-family: var(--mono);
}

.isoball span {
  font-size: var(--t-xs);
  color: var(--ink-3);
}

/* ============================================================
   shared: a small stat strip
   ============================================================ */

.statstrip {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(110px, 1fr));
  gap: var(--s-2);
  margin-top: var(--s-3);
}

.statstrip > div {
  padding: 9px 12px;
  border-radius: var(--r-sm);
  border: 1px solid var(--line);
  background: var(--surface-2);
}

/* Direct children only. A bare `.statstrip span` also matches the
   element pills that get dropped into these cells, turning an inline
   badge into a full-width block — the pill stretches across the card and
   the name falls onto the next line. */
.statstrip > div > span {
  display: block;
  font-size: var(--t-xs);
  color: var(--ink-3);
}

.statstrip b {
  font-size: var(--t-md);
  font-variant-numeric: tabular-nums;
}

/* A tidy inline element pill, used in prose and in feedback. It carries
   the symbol AND the name — see PTE.render.pill for why. The symbol is
   the bold half so it still reads as a chemical symbol, and the name
   sits beside it slightly smaller. */
.epill {
  --pc: var(--ink-3);
  display: inline-flex;
  align-items: baseline;
  gap: 5px;
  padding: 1px 9px;
  border-radius: var(--r-pill);
  border: 1px solid color-mix(in srgb, var(--pc) 45%, transparent);
  background: color-mix(in srgb, var(--pc) 14%, transparent);
  font-size: 0.95em;
  white-space: nowrap;
}

.epill b {
  font-weight: 700;
}

.epill__name {
  font-weight: 600;
  font-size: 0.92em;
  color: var(--ink-2);
}

.epill small {
  font-weight: 600;
  color: var(--ink-3);
  font-size: 0.8em;
}

/* Element chips — the walks in §08 and the metal picker in §12 — carry
   the name for the same reason the pills do. Lighter than the symbol so
   the symbol still reads as the symbol. */
.chip__name {
  font-weight: 550;
  color: var(--ink-3);
  margin-left: 5px;
}

.chip.is-on .chip__name {
  color: var(--ink-2);
}

.epill[data-cat="alkali"] { --pc: var(--cat-alkali); }
.epill[data-cat="alkaline"] { --pc: var(--cat-alkaline); }
.epill[data-cat="transition"] { --pc: var(--cat-transition); }
.epill[data-cat="post"] { --pc: var(--cat-post); }
.epill[data-cat="metalloid"] { --pc: var(--cat-metalloid); }
.epill[data-cat="nonmetal"] { --pc: var(--cat-nonmetal); }
.epill[data-cat="halogen"] { --pc: var(--cat-halogen); }
.epill[data-cat="noble"] { --pc: var(--cat-noble); }
.epill[data-cat="lanthanide"] { --pc: var(--cat-lanthanide); }
.epill[data-cat="actinide"] { --pc: var(--cat-actinide); }