:root {
  color-scheme: dark;
  --bg: #101114;
  --surface: #181a1f;
  --surface-2: #20232a;
  --line: #30343d;
  --muted: #a7adb7;
  --text: #f3f4f7;
  /* Tracks the selected element's periodic-table (block) color; set from JS. */
  --element-accent: var(--accent);
  --focus: #ffd166;
  --stage-bg: #06070a;
  --nucleus: #f0f7ff;
  --s-color: #3e79ad;
  --p-color: #6f9fca;
  --d-color: #17395f;
  --f-color: #b8d6f0;
  --accent: #6f9fca;
  --page-sheen: linear-gradient(180deg, rgba(255, 255, 255, 0.04), rgba(255, 255, 255, 0) 32rem);
  --topbar-bg: rgba(16, 17, 20, 0.88);
  --frame-sheen: linear-gradient(135deg, rgba(255, 255, 255, 0.08), rgba(255, 255, 255, 0));
  --panel-glow: color-mix(in srgb, var(--element-accent), transparent 58%);
  --shadow-strong: rgba(0, 0, 0, 0.35);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

:root[data-theme="bright"] {
  color-scheme: light;
  --bg: #f5f7fb;
  --surface: #ffffff;
  --surface-2: #eef2f7;
  --line: #cfd7e6;
  --muted: #5d6878;
  --text: #101828;
  --stage-bg: #ffffff;
  --nucleus: #182a3c;
  --s-color: #1f5c8a;
  --p-color: #476f98;
  --d-color: #102d4d;
  --f-color: #7599bb;
  --accent: #476f98;
  --focus: #a96500;
  --page-sheen: linear-gradient(180deg, rgba(77, 215, 200, 0.12), rgba(255, 255, 255, 0) 30rem);
  --topbar-bg: rgba(245, 247, 251, 0.9);
  --frame-sheen: linear-gradient(135deg, rgba(16, 24, 40, 0.08), rgba(16, 24, 40, 0));
  --panel-glow: color-mix(in srgb, var(--element-accent), transparent 72%);
  --shadow-strong: rgba(16, 24, 40, 0.18);
}

* {
  box-sizing: border-box;
}

html {
  min-height: 100%;
  background: var(--bg);
}

body {
  min-height: 100vh;
  margin: 0;
  background:
    var(--page-sheen),
    var(--bg);
  color: var(--text);
}

.stage,
#atomSvg,
.orbital-card,
.orbital-card svg {
  user-select: none;
  -webkit-user-select: none;
}

button,
input,
select {
  font: inherit;
  letter-spacing: 0;
}

button {
  border: 1px solid var(--line);
  border-radius: 7px;
  background: var(--surface-2);
  color: var(--text);
  cursor: pointer;
  min-height: 2.5rem;
  padding: 0 0.85rem;
}

button:hover {
  border-color: color-mix(in srgb, var(--accent), white 18%);
  background: color-mix(in srgb, var(--surface-2), var(--accent) 12%);
}

button:focus-visible,
input:focus-visible,
select:focus-visible {
  outline: 2px solid var(--focus);
  outline-offset: 2px;
}

.app-shell {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 1rem clamp(1rem, 3vw, 2rem);
  border-bottom: 1px solid var(--line);
  background: var(--topbar-bg);
  backdrop-filter: blur(14px);
  position: sticky;
  top: 0;
  z-index: 5;
}

.brand {
  min-width: 0;
  display: flex;
  align-items: center;
  gap: 0.8rem;
}

.brand-mark {
  width: 2.4rem;
  height: 2.4rem;
  border-radius: 50%;
  display: inline-grid;
  place-items: center;
  background:
    radial-gradient(circle at 50% 50%, var(--nucleus) 0 12%, transparent 13%),
    conic-gradient(from 90deg, var(--s-color), var(--p-color), var(--d-color), var(--f-color), var(--s-color));
  box-shadow: 0 0 2rem color-mix(in srgb, var(--accent), transparent 58%);
}

.brand h1,
.brand p,
.panel h2,
.orbital-header h2 {
  margin: 0;
  letter-spacing: 0;
}

.brand h1 {
  font-size: clamp(1.15rem, 1rem + 0.8vw, 1.65rem);
  line-height: 1.1;
}

.brand p {
  color: var(--muted);
  font-size: 0.88rem;
  margin-top: 0.2rem;
}

.top-actions {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  justify-content: flex-end;
}

.top-actions button {
  white-space: nowrap;
}

.theme-toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.55rem;
  min-width: 6.4rem;
}

.theme-toggle__track {
  position: relative;
  width: 2.2rem;
  height: 1.2rem;
  flex: 0 0 auto;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--surface);
}

.theme-toggle__thumb {
  position: absolute;
  top: 0.2rem;
  left: 0.2rem;
  width: 0.7rem;
  height: 0.7rem;
  border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 0 0.8rem color-mix(in srgb, var(--accent), transparent 45%);
  transition: transform 180ms ease;
}

.theme-toggle__label {
  font-size: 0.9rem;
  line-height: 1;
}

:root[data-theme="bright"] .theme-toggle__thumb {
  transform: translateX(1rem);
}

.layout {
  flex: 1;
  display: block;
  padding: clamp(1rem, 3vw, 2rem);
}

.workspace {
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.overview-row {
  display: grid;
  grid-template-columns: minmax(0, 1.4fr) minmax(10rem, 0.32fr) minmax(18rem, 0.92fr);
  gap: 1rem;
  align-items: stretch;
}

.element-select-panel {
  display: grid;
  align-content: start;
  gap: 0.55rem;
  overflow: hidden;
}

.panel.element-select-panel h2 {
  margin-bottom: 0;
}

.periodic-table-scroll {
  max-width: 100%;
  overflow: hidden;
  scrollbar-color: color-mix(in srgb, var(--accent), transparent 42%) transparent;
}

.periodic-table {
  display: grid;
  grid-template-columns: repeat(18, minmax(1.65rem, 1fr));
  grid-template-rows: repeat(9, clamp(1.85rem, 1.6vw, 3.05rem));
  gap: clamp(0.14rem, 0.14vw, 0.28rem);
}

.periodic-element {
  --block-color: var(--accent);
  min-width: 0;
  min-height: 0;
  height: 100%;
  display: grid;
  grid-template-rows: auto 1fr;
  align-items: center;
  justify-items: start;
  gap: 0.05rem;
  border-color: color-mix(in srgb, var(--block-color), var(--line) 64%);
  border-radius: 6px;
  background:
    linear-gradient(180deg, color-mix(in srgb, var(--block-color), transparent 82%), transparent),
    var(--surface-2);
  box-shadow: inset 0 0 0 1px color-mix(in srgb, white, transparent 96%);
  padding: 0.14rem 0.16rem;
  text-align: left;
}

.periodic-element[data-block="s"] {
  --block-color: var(--s-color);
}

.periodic-element[data-block="p"] {
  --block-color: var(--p-color);
}

.periodic-element[data-block="d"] {
  --block-color: var(--d-color);
}

.periodic-element[data-block="f"] {
  --block-color: var(--f-color);
}

.periodic-element:hover {
  border-color: color-mix(in srgb, var(--block-color), white 18%);
  background:
    linear-gradient(180deg, color-mix(in srgb, var(--block-color), transparent 70%), transparent),
    color-mix(in srgb, var(--surface-2), var(--block-color) 12%);
}

.periodic-element.is-selected {
  border-color: color-mix(in srgb, var(--block-color), white 30%);
  background:
    linear-gradient(180deg, color-mix(in srgb, var(--block-color), transparent 48%), transparent),
    color-mix(in srgb, var(--surface-2), var(--block-color) 22%);
  box-shadow:
    inset 0 0 0 1px color-mix(in srgb, var(--block-color), white 26%),
    0 0 0.85rem color-mix(in srgb, var(--block-color), transparent 74%);
}

.periodic-element__number {
  color: color-mix(in srgb, var(--muted), var(--block-color) 30%);
  font-size: clamp(0.46rem, 0.4vw, 0.68rem);
  font-variant-numeric: tabular-nums;
  line-height: 1;
}

.periodic-element__symbol {
  align-self: end;
  color: var(--text);
  font-size: clamp(0.76rem, 0.62vw, 1.12rem);
  line-height: 1;
}

.config-panel {
  min-height: 100%;
}

.solver-controls {
  display: grid;
  grid-template-columns: minmax(13rem, 0.42fr) minmax(15rem, 1fr);
  gap: 0.75rem;
  align-items: end;
}

.control-card {
  gap: 0.75rem;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
  padding: 1rem;
}

.dimension-bar {
  display: grid;
  grid-template-columns: minmax(12rem, 18rem);
  align-items: end;
}

.mode-bar {
  display: grid;
  grid-template-columns: repeat(2, minmax(12rem, 1fr));
  align-items: end;
}

.option-bar {
  position: relative;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(10rem, 1fr)) auto;
  align-items: end;
}

.control-card-title {
  grid-column: 1 / -1;
  margin: 0;
  color: var(--muted);
  font-size: 0.88rem;
  font-weight: 700;
  letter-spacing: 0;
  text-transform: uppercase;
}

.option-bar:empty,
.option-bar[hidden],
.stage-wrap[hidden],
.orbital-section[hidden] {
  display: none;
}

[hidden] {
  display: none !important;
}

.segmented {
  min-height: 2.6rem;
  display: inline-grid;
  grid-template-columns: repeat(3, minmax(3.5rem, 1fr));
  align-self: end;
  width: 100%;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
  padding: 0.2rem;
}

.segmented button {
  min-height: 2.65rem;
  border: 0;
  border-radius: 6px;
  background: transparent;
  color: var(--muted);
  padding: 0 0.85rem;
}

.segmented button.is-active {
  background: color-mix(in srgb, var(--accent), var(--surface-2) 72%);
  color: var(--text);
}

.field {
  display: grid;
  gap: 0.4rem;
  color: var(--muted);
  font-size: 0.82rem;
}

textarea {
  width: 100%;
  min-height: 5.25rem;
  resize: vertical;
  border: 1px solid var(--line);
  border-radius: 7px;
  background: var(--surface);
  color: var(--text);
  padding: 0.75rem;
  line-height: 1.45;
}

textarea::placeholder {
  color: color-mix(in srgb, var(--muted), transparent 16%);
}

.checkbox-field {
  min-width: 8.5rem;
}

.export-options-field {
  min-width: min(100%, 18rem);
}

.export-option-row {
  display: flex;
  align-items: center;
  gap: 0.9rem;
  flex-wrap: wrap;
  min-height: 2.6rem;
}

.export-option-row .checkbox-control {
  min-height: auto;
}

.checkbox-control {
  display: inline-flex;
  align-items: center;
  gap: 0.55rem;
  min-height: 2.6rem;
  color: var(--text);
}

.checkbox-control input {
  width: 1.05rem;
  height: 1.05rem;
  margin: 0;
  accent-color: var(--accent);
}

select {
  width: 100%;
  min-height: 2.6rem;
  border: 1px solid var(--line);
  border-radius: 7px;
  background: var(--surface);
  color: var(--text);
  padding: 0 0.75rem;
}

select:disabled {
  color: color-mix(in srgb, var(--muted), transparent 18%);
  cursor: not-allowed;
  background: color-mix(in srgb, var(--surface), var(--bg) 45%);
}

input[type="range"] {
  width: 100%;
  min-height: 2.6rem;
  accent-color: var(--accent);
}

.probability-field output,
.artsy-speed-field output {
  color: var(--text);
  font-variant-numeric: tabular-nums;
  margin-left: 0.35rem;
}

.stage-wrap {
  position: relative;
  min-width: 0;
  padding: 1px;
  border: 1px solid var(--line);
  background: var(--frame-sheen);
}

.stage {
  min-height: clamp(24rem, 68vh, 64rem);
  display: grid;
  place-items: center;
  background: var(--stage-bg);
  overflow: hidden;
}

/* Canvas (iso-surface) and SVG (overlays) share one grid cell so they overlap. */
.stage > #atomCanvas,
.stage > #atomSvg {
  grid-area: 1 / 1;
}

#atomSvg {
  width: min(100%, 64rem);
  height: min(82vh, 64rem);
  max-height: 100%;
  display: block;
  touch-action: none;
}

#atomCanvas {
  width: min(100%, 64rem);
  height: min(82vh, 64rem);
  max-height: 100%;
  object-fit: contain;
  display: none;
  pointer-events: none;
}

#atomCanvas.is-active {
  display: block;
}

#atomSvg.is-3d {
  cursor: grab;
}

#atomSvg.is-3d.is-dragging {
  cursor: grabbing;
}

#atomSvg.is-artsy {
  touch-action: auto;
}

.orbital-header {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 1rem;
  margin-top: 0.25rem;
}

.orbital-section {
  display: grid;
  gap: 1rem;
}

.feature-request-dialog[hidden] {
  display: none;
}

.feature-request-dialog {
  position: fixed;
  inset: 0;
  z-index: 20;
  display: grid;
  justify-items: end;
  align-items: start;
  padding: calc(4.9rem + env(safe-area-inset-top, 0px)) clamp(1rem, 3vw, 2rem) 1rem;
  pointer-events: none;
}

.feature-request-backdrop {
  position: absolute;
  inset: 0;
  width: 100%;
  min-height: 0;
  border: 0;
  border-radius: 0;
  padding: 0;
  background: rgba(0, 0, 0, 0.36);
  cursor: default;
  pointer-events: auto;
}

:root[data-theme="bright"] .feature-request-backdrop {
  background: rgba(16, 24, 40, 0.18);
}

.feature-request-popover {
  position: relative;
  z-index: 1;
  width: min(34rem, calc(100vw - 2rem));
  display: grid;
  gap: 1rem;
  box-shadow: 0 1.2rem 3rem var(--shadow-strong);
  pointer-events: auto;
}

.feature-request-copy {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 1rem;
}

.feature-request-copy p {
  margin: 0;
  color: var(--muted);
  font-size: 0.9rem;
  line-height: 1.45;
}

.feature-request-close {
  flex: 0 0 auto;
  min-height: 2rem;
  padding: 0 0.65rem;
  font-size: 0.82rem;
}

.feature-request-form {
  display: grid;
  gap: 0.75rem;
}

.feature-request-field textarea {
  min-height: 5.5rem;
}

.feature-request-actions {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  flex-wrap: wrap;
}

.feature-request-actions button:disabled {
  cursor: wait;
  opacity: 0.68;
}

.feature-request-status {
  min-height: 1.25rem;
  margin: 0;
  color: var(--muted);
  font-size: 0.86rem;
  line-height: 1.4;
}

.feature-request-status[data-tone="success"] {
  color: color-mix(in srgb, var(--accent), var(--text) 26%);
}

.feature-request-status[data-tone="error"] {
  color: #ff9a9a;
}

  :root[data-theme="bright"] .feature-request-status[data-tone="error"] {
    color: #a63d3d;
  }

.orbital-header h2,
.panel h2 {
  font-size: 0.88rem;
  text-transform: uppercase;
  color: var(--muted);
  font-weight: 700;
}

#orbitalCount {
  color: var(--muted);
  font-size: 0.84rem;
}

.orbital-grid {
  display: flex;
  flex-direction: column;
  align-items: stretch;
  gap: 1.15rem;
  overflow-x: auto;
  padding-bottom: 0.25rem;
}

.orbital-row {
  width: max-content;
  max-width: none;
  margin-inline: auto;
  display: flex;
  justify-content: center;
  gap: 1rem;
}

.orbital-card {
  flex: 0 0 clamp(14rem, 17vw, 18rem);
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
  width: clamp(14rem, 17vw, 18rem);
  min-width: 0;
  overflow: hidden;
}

.orbital-card svg {
  width: 100%;
  height: auto;
  aspect-ratio: 1;
  display: block;
  background: var(--stage-bg);
}

.orbital-card svg.is-3d-card {
  cursor: grab;
  touch-action: none;
}

.orbital-card svg.is-3d-card.is-dragging {
  cursor: grabbing;
}

.orbital-meta {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 0.35rem 0.5rem;
  padding: 0.65rem 0.7rem 0.7rem;
  align-items: baseline;
}

.orbital-meta strong {
  min-width: 0;
  overflow-wrap: anywhere;
  font-size: 0.95rem;
}

.orbital-meta span {
  color: var(--muted);
  font-size: 0.78rem;
}

.occupancy {
  justify-self: end;
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 0.12rem 0.45rem;
  color: var(--text);
}

.inspector {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  min-width: 0;
}

.panel {
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
  padding: 1rem;
  min-width: 0;
}

.panel h2 {
  margin-bottom: 0.85rem;
}

.atom-panel {
  display: grid;
  align-content: center;
  min-height: 100%;
  background:
    radial-gradient(circle at 85% 15%, var(--panel-glow), transparent 12rem),
    var(--surface);
}

.element-chip {
  display: grid;
  grid-template-columns: auto 1fr;
  grid-template-areas:
    "number symbol"
    "name name";
  gap: 0.1rem 0.85rem;
  align-items: end;
}

#elementNumber {
  grid-area: number;
  color: var(--muted);
  font-size: 1.05rem;
  padding-bottom: 0.35rem;
}

#elementSymbol {
  grid-area: symbol;
  font-size: clamp(3rem, 8vw, 5rem);
  line-height: 0.95;
  color: color-mix(in srgb, var(--element-accent), var(--text) 32%);
}

#elementName {
  grid-area: name;
  color: var(--muted);
  font-size: 1rem;
}

.config-line {
  font-size: 1.25rem;
  line-height: 1.6;
  overflow-wrap: anywhere;
}

.config-full {
  color: var(--muted);
  font-size: 0.86rem;
  line-height: 1.5;
  margin-top: 0.6rem;
  overflow-wrap: anywhere;
}

.subshell-list {
  display: grid;
  gap: 0.65rem;
  margin-top: 0.9rem;
}

.subshell-map-legend {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem 0.85rem;
  align-items: center;
  margin-bottom: 0.15rem;
}

.subshell-legend-item {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  color: var(--muted);
  font-size: 0.75rem;
  line-height: 1.2;
  white-space: nowrap;
}

.subshell-legend-swatch {
  width: 1.35rem;
  height: 0.9rem;
  flex: 0 0 auto;
  border: 1px solid var(--line);
  border-radius: 4px;
  background: var(--surface-2);
}

.subshell-legend-item.is-valence .subshell-legend-swatch {
  border-color: color-mix(in srgb, white, var(--accent) 24%);
  background:
    linear-gradient(90deg,
      var(--s-color) 0 25%,
      var(--p-color) 25% 50%,
      var(--d-color) 50% 75%,
      var(--f-color) 75% 100%);
  box-shadow:
    inset 0 0 0 1px color-mix(in srgb, white, transparent 52%),
    0 0 0 2px color-mix(in srgb, var(--accent), transparent 72%);
}

.subshell-legend-item.is-closed-shell .subshell-legend-swatch {
  border-color: color-mix(in srgb, var(--muted), white 12%);
  background:
    repeating-linear-gradient(
      135deg,
      color-mix(in srgb, var(--muted), transparent 88%) 0 3px,
      transparent 3px 6px
    ),
    color-mix(in srgb, var(--surface-2), var(--muted) 18%);
  box-shadow:
    inset 0 0 0 2px color-mix(in srgb, var(--muted), transparent 52%),
    0 0 0 1px color-mix(in srgb, var(--muted), transparent 76%);
}

.subshell-legend-item.is-empty .subshell-legend-swatch {
  border-color: color-mix(in srgb, var(--line), var(--muted) 28%);
  background: color-mix(in srgb, var(--surface-2), var(--muted) 8%);
  opacity: 0.62;
}

.subshell-map-grid {
  display: grid;
  gap: 0.5rem;
}

.subshell-map-row {
  display: grid;
  grid-template-columns: 3.9rem minmax(0, 1fr);
  gap: 0.55rem;
  align-items: center;
}

.subshell-level {
  color: var(--muted);
  font-size: 0.78rem;
  line-height: 1.1;
  white-space: nowrap;
}

.subshell-map-cells {
  min-width: 0;
  display: grid;
  grid-template-columns: repeat(var(--subshell-columns, 4), minmax(2.85rem, 1fr));
  gap: 0.35rem;
}

.subshell-tile {
  --orbital-color: var(--accent);
  position: relative;
  isolation: isolate;
  min-width: 0;
  min-height: 3.1rem;
  display: grid;
  grid-template-columns: 1fr auto;
  align-items: start;
  gap: 0.2rem;
  overflow: hidden;
  border: 1px solid color-mix(in srgb, var(--orbital-color), var(--line) 64%);
  border-radius: 8px;
  background:
    linear-gradient(180deg, color-mix(in srgb, var(--orbital-color), transparent 88%), transparent),
    var(--surface-2);
  padding: 0.45rem;
  box-shadow: inset 0 0 0 1px color-mix(in srgb, white, transparent 96%);
}

.subshell-tile::before {
  content: "";
  position: absolute;
  inset: auto 0 0;
  z-index: -1;
  height: var(--tile-fill, 0%);
  background:
    linear-gradient(180deg, transparent, color-mix(in srgb, var(--orbital-color), transparent 58%));
}

.subshell-tile[data-l="s"] {
  --orbital-color: var(--s-color);
}

.subshell-tile[data-l="p"] {
  --orbital-color: var(--p-color);
}

.subshell-tile[data-l="d"] {
  --orbital-color: var(--d-color);
}

.subshell-tile[data-l="f"] {
  --orbital-color: var(--f-color);
}

.subshell-tile.is-valence {
  border-color: color-mix(in srgb, var(--orbital-color), white 34%);
  background:
    linear-gradient(180deg, color-mix(in srgb, var(--orbital-color), transparent 78%), transparent),
    color-mix(in srgb, var(--surface-2), var(--orbital-color) 8%);
  box-shadow:
    inset 0 0 0 1px color-mix(in srgb, white, transparent 70%),
    0 0 0 2px color-mix(in srgb, var(--orbital-color), transparent 64%),
    0 0 0.95rem color-mix(in srgb, var(--orbital-color), transparent 76%);
}

.subshell-tile.is-valence::before {
  background:
    linear-gradient(180deg, transparent, color-mix(in srgb, var(--orbital-color), transparent 38%));
}

.subshell-tile.is-closed-shell {
  border-color: color-mix(in srgb, var(--muted), white 10%);
  background:
    repeating-linear-gradient(
      135deg,
      color-mix(in srgb, var(--muted), transparent 91%) 0 6px,
      transparent 6px 12px
    ),
    color-mix(in srgb, var(--surface-2), var(--muted) 14%);
  box-shadow:
    inset 0 0 0 2px color-mix(in srgb, var(--muted), transparent 50%),
    inset 0 0 0 1px color-mix(in srgb, white, transparent 96%);
}

.subshell-tile.is-closed-shell::before {
  background:
    linear-gradient(180deg, transparent, color-mix(in srgb, var(--muted), transparent 76%));
  opacity: 0.46;
}

.subshell-tile.is-empty {
  border-color: color-mix(in srgb, var(--line), var(--muted) 18%);
  background: color-mix(in srgb, var(--surface-2), var(--muted) 5%);
  opacity: 0.66;
}

.subshell-tile.is-empty::before {
  display: none;
}

.subshell-tile-label {
  color: var(--text);
  font-size: 1rem;
  line-height: 1;
}

.subshell-electron-count {
  align-self: end;
  justify-self: end;
  display: inline-flex;
  align-items: baseline;
  gap: 0.06rem;
  color: color-mix(in srgb, var(--orbital-color), var(--text) 30%);
  line-height: 1;
  white-space: nowrap;
}

.subshell-electron-count strong {
  font-size: 1.18rem;
  font-variant-numeric: tabular-nums;
}

.subshell-electron-count span {
  color: var(--muted);
  font-size: 0.72rem;
  font-weight: 700;
}

.subshell-tile.is-closed-shell .subshell-electron-count {
  color: color-mix(in srgb, var(--muted), var(--text) 12%);
}

.subshell-tile.is-closed-shell .subshell-tile-label {
  color: color-mix(in srgb, var(--text), var(--muted) 42%);
}

.subshell-tile.is-empty .subshell-tile-label,
.subshell-tile.is-empty .subshell-electron-count {
  color: var(--muted);
}

.color-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.7rem;
  margin-top: 0.85rem;
}

.color-grid label {
  display: grid;
  gap: 0.4rem;
  color: var(--muted);
  font-size: 0.82rem;
}

.shell-color-section {
  grid-column: 1 / -1;
  display: grid;
  gap: 0.5rem;
  padding-top: 0.1rem;
}

.shell-color-section > span {
  color: var(--muted);
  font-size: 0.82rem;
}

.shell-color-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(4.4rem, 1fr));
  gap: 0.55rem;
}

.shell-color-grid label {
  display: grid;
  gap: 0.35rem;
  color: color-mix(in srgb, var(--muted), var(--text) 10%);
  font-size: 0.78rem;
}

input[type="color"] {
  width: 100%;
  height: 2.5rem;
  border: 1px solid var(--line);
  border-radius: 7px;
  background: var(--surface-2);
  padding: 0.25rem;
}

.solver-panel {
  display: grid;
  gap: 0.85rem;
}

.color-panel {
  position: relative;
  align-self: end;
  justify-self: end;
}

.color-panel-toggle {
  width: 2.6rem;
  min-height: 2.6rem;
  display: inline-grid;
  place-items: center;
  border-radius: 7px;
  background: var(--surface);
  padding: 0;
}

.color-panel-toggle:hover {
  background: color-mix(in srgb, var(--surface-2), var(--accent) 8%);
}

.palette-icon {
  width: 1.35rem;
  height: 1.35rem;
  border: 1px solid var(--line);
  border-radius: 50%;
  background:
    radial-gradient(circle at 50% 50%, var(--surface) 0 18%, transparent 19%),
    conic-gradient(var(--s-color), var(--p-color), var(--d-color), var(--f-color), var(--s-color));
  box-shadow: 0 0 0.7rem color-mix(in srgb, var(--accent), transparent 76%);
}

.color-panel-toggle[aria-expanded="true"] {
  border-color: color-mix(in srgb, var(--accent), white 18%);
  background: color-mix(in srgb, var(--surface-2), var(--accent) 14%);
}

.color-panel-body {
  position: absolute;
  right: 0;
  top: calc(100% + 0.5rem);
  z-index: 8;
  width: min(22rem, calc(100vw - 2rem));
  display: grid;
  gap: 0.85rem;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
  box-shadow: 0 1rem 3rem var(--shadow-strong);
  padding: 1rem;
}

.solver-panel h2 {
  margin-bottom: 0;
}

.solver-link {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  border: 1px solid var(--line);
  border-radius: 7px;
  color: var(--text);
  background: color-mix(in srgb, var(--surface-2), var(--element-accent) 8%);
  min-height: 2.6rem;
  padding: 0 0.75rem;
  text-decoration: none;
  line-height: 1.35;
}

.solver-link::after {
  content: "Open";
  flex: 0 0 auto;
  border: 1px solid color-mix(in srgb, var(--element-accent), var(--line) 45%);
  border-radius: 999px;
  color: var(--text);
  background: color-mix(in srgb, var(--element-accent), transparent 80%);
  padding: 0.18rem 0.55rem;
  font-size: 0.78rem;
  font-weight: 700;
}

.solver-link:hover {
  border-color: color-mix(in srgb, var(--element-accent), white 16%);
  background: color-mix(in srgb, var(--surface-2), var(--element-accent) 16%);
}

.toast {
  position: fixed;
  right: 1rem;
  bottom: 1rem;
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--text);
  padding: 0.75rem 0.9rem;
  border-radius: 8px;
  box-shadow: 0 1rem 3rem var(--shadow-strong);
  z-index: 10;
}

.screen-reader-only {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
}

@media (max-width: 980px) {
  .overview-row {
    grid-template-columns: minmax(25rem, 1fr) minmax(8.5rem, 0.45fr);
    align-items: stretch;
  }

  .config-panel {
    grid-column: 1 / -1;
  }

  .solver-controls {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 720px) {
  .topbar,
  .orbital-header {
    align-items: stretch;
    flex-direction: column;
  }

  .top-actions {
    justify-content: stretch;
  }

  .top-actions button {
    flex: 1;
  }

  .dimension-bar,
  .option-bar,
  .inspector {
    grid-template-columns: 1fr;
  }

  .overview-row {
    grid-template-columns: 1fr;
  }

  .config-panel {
    grid-column: auto;
  }

  .periodic-table-scroll {
    overflow-x: auto;
    overflow-y: hidden;
    padding-bottom: 0.35rem;
    -webkit-overflow-scrolling: touch;
  }

  .periodic-table {
    min-width: 54rem;
    grid-template-columns: repeat(18, minmax(1.85rem, 1fr));
    grid-template-rows: repeat(9, 2.75rem);
    gap: 0.22rem;
  }

  .periodic-element {
    padding: 0.24rem 0.3rem;
  }

  .periodic-element__number {
    font-size: 0.52rem;
  }

  .periodic-element__symbol {
    font-size: 0.84rem;
  }

  .segmented {
    width: 100%;
  }

  .stage {
    min-height: 22rem;
  }

  #atomSvg {
    height: auto;
    aspect-ratio: 1;
  }

}

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

@media (max-width: 430px) {
  .periodic-table {
    min-width: 52rem;
    grid-template-rows: repeat(9, 2.65rem);
  }

  .top-actions {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .top-actions button {
    width: 100%;
    min-width: 0;
  }

  .top-actions button:last-child {
    grid-column: 1 / -1;
  }
}