:root {
  color-scheme:light;
  --ink:#17264a;
  --muted:#50617d;
  --paper:#fff;
  --page:#ffffff;
  --line:#cbd6ec;
  --primary:#2a3f96;
  --primary-hover:#1d2c70;
  --wash:#edf3ff;
  --retry:#304c87;
  --retry-wash:#e4edff;
  --focus:#1165bd;
  --radius:12px;
  font-family:Arial,Helvetica,sans-serif;
  color:var(--ink);
  background:var(--page);
  font-size:16px;
  line-height:1.5
}

* {
  box-sizing:border-box
}

body {
  margin:0
}

button,input,select {
  font:inherit
}

button,select,label,summary {
  -webkit-tap-highlight-color:transparent
}

button,select {
  min-height:44px
}

button,summary {
  cursor:pointer
}

button {
  border:0
}

button:disabled {
  cursor:default
}

button:focus-visible,a:focus-visible,input:focus-visible,select:focus-visible,summary:focus-visible,[tabindex]:focus-visible {
  outline:3px solid var(--focus);
  outline-offset:4px
}

::selection {
  background:#cfdfef;
  color:#102f50
}

a {
  color:var(--primary);
  text-underline-offset:4px
}

a:hover {
  text-decoration-thickness:2px
}

[hidden] {
  display:none!important
}

.sr-only {
  position:absolute;
  width:1px;
  height:1px;
  padding:0;
  overflow:hidden;
  clip-path:inset(50%);
  white-space:nowrap
}

.skip-link {
  position:absolute;
  top:8px;
  left:12px;
  z-index:2;
  transform:translateY(-150%);
  padding:12px;
  background:#fff
}

.skip-link:focus {
  transform:none
}

.site-header,main,footer {
  max-width:1120px;
  margin-inline:auto;
  padding-inline:32px
}

.site-header {
  min-height:154px;
  padding-block:20px;
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap:24px;
  border-bottom:1px solid var(--line)
}

.brand {
  display:block;
  flex:0 1 640px;
  min-width:0;
  text-decoration:none
}

.brand img {
  display:block;
  width:100%;
  height:auto
}

.language {
  flex-shrink:0;
  display:flex;
  align-items:center;
  gap:10px;
  font-size:14px
}

.language select {
  width:auto;
  padding-right:28px
}

.page-heading {
  padding-block:32px 25px
}

h1 {
  font-size:32px;
  letter-spacing:-.025em;
  line-height:1.2;
  margin:0 0 8px
}

h2 {
  font-size:25px;
  line-height:1.25;
  letter-spacing:-.015em
}

h3 {
  font-size:18px;
  line-height:1.35
}

p {
  margin:0 0 16px
}

.page-heading p {
  color:var(--muted);
  margin:0;
  max-width:65ch
}

.workspace {
  display:grid;
  grid-template-columns:280px minmax(0,1fr);
  gap:32px;
  align-items:start;
  padding-bottom:44px
}

.settings-panel {
  padding:22px;
  background:#f0f5ff;
  border-radius:var(--radius)
}

summary {
  font-weight:700
}

.settings-panel summary {
  font-size:18px;
  line-height:1.4;
  padding-block:2px 8px
}

.settings-panel summary::marker,footer summary::marker,.result-details summary::marker {
  color:var(--primary)
}

fieldset {
  border:0;
  margin:0;
  padding:0;
  min-width:0
}

legend,.control-label {
  font-weight:700;
  font-size:14px;
  margin-bottom:10px;
  padding:0
}

form>fieldset>fieldset,form>fieldset>div {
  margin-top:20px
}

.control-label {
  display:block;
  margin-top:20px
}

select {
  width:100%;
  padding:8px 10px;
  border:1px solid #a9bad9;
  border-radius:6px;
  background:#fff;
  color:var(--ink);
  max-width:100%
}

select:disabled {
  background:#f2f5fb;
  color:var(--muted)
}

fieldset:disabled .operation-options,fieldset:disabled .row-options,fieldset:disabled .preset-options {
  opacity:.58
}

.operation-options {
  display:grid;
  grid-template-columns:1fr 1fr;
  gap:8px
}

.operation-options label,.row-options label {
  position:relative;
  cursor:pointer
}

.operation-options input,.row-options input {
  position:absolute;
  opacity:0;
  width:1px;
  height:1px
}

.operation-options label>span {
  display:flex;
  align-items:center;
  gap:10px;
  padding:10px 12px;
  min-height:48px;
  border:1px solid #b8c8e3;
  border-radius:7px;
  background:#fff;
  font-size:14px
}

.operation-options b {
  font-size:25px;
  line-height:1;
  font-weight:400;
  width:18px;
  text-align:center
}

.operation-options input:checked+span,.row-options input:checked+span {
  background:var(--primary);
  color:#fff;
  border-color:var(--primary)
}

.operation-options input:focus-visible+span,.row-options input:focus-visible+span {
  outline:3px solid var(--focus);
  outline-offset:3px
}

.operation-options label:hover>span,.row-options label:hover>span {
  border-color:var(--primary)
}

.row-options {
  display:grid;
  grid-template-columns:repeat(4,1fr);
  gap:6px
}

.row-options span {
  display:grid;
  place-items:center;
  background:#fff;
  border:1px solid #b8c8e3;
  border-radius:6px;
  min-height:44px;
  font-variant-numeric:tabular-nums
}

.preset-options {
  display:flex;
  flex-wrap:wrap;
  gap:4px 16px;
  margin-top:8px
}

.text-button {
  padding:6px 0;
  background:transparent;
  color:var(--primary);
  text-decoration:underline;
  text-underline-offset:4px;
  font-weight:700;
  font-size:14px
}

.text-button:hover {
  color:var(--primary-hover);
  text-decoration-thickness:2px
}

.field-note {
  font-size:12px;
  color:var(--muted);
  line-height:1.5;
  margin:9px 0 0
}

.primary,.secondary {
  border-radius:7px;
  padding:11px 18px;
  font-weight:700;
  line-height:1.4
}

.primary {
  background:var(--primary);
  color:#fff
}

.primary:hover {
  background:var(--primary-hover)
}

.secondary {
  background:#fff;
  color:var(--primary);
  border:1px solid #98acd1
}

.secondary:hover {
  background:var(--wash)
}

.primary:disabled {
  background:#becbe4;
  color:#334971
}

.full-width {
  width:100%;
  margin-top:20px
}

.form-error {
  font-size:14px;
  color:#2a3f76;
  margin-top:16px
}

#round-selection p {
  font-size:14px;
  margin-top:16px;
  margin-bottom:0;
  font-weight:700
}

.reset-confirm {
  border-top:1px solid #b8c8e3;
  margin-top:20px;
  padding-top:16px;
  font-size:14px
}

.actions {
  display:flex;
  flex-wrap:wrap;
  gap:12px
}

.play-area {
  min-width:0;
  background:#fff;
  border:1px solid var(--line);
  border-radius:var(--radius);
  padding:28px 32px
}

.welcome {
  padding-block:20px
}

.welcome h2 {
  margin:0 0 18px
}

.welcome p {
  max-width:56ch
}

.welcome ol {
  padding-left:24px;
  max-width:48ch;
  margin:28px 0
}

.welcome li {
  padding-left:8px;
  margin-block:18px
}

.welcome li::marker {
  color:var(--primary);
  font-weight:700
}

.ready-foot {
  color:var(--primary);
  font-weight:700;
  border-top:1px solid var(--line);
  padding-top:24px;
  margin-bottom:0
}

.round-progress {
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap:16px;
  color:var(--muted);
  font-size:13px;
  font-variant-numeric:tabular-nums
}

progress {
  appearance:none;
  height:6px;
  border:0;
  width:100px;
  border-radius:3px;
  overflow:hidden;
  background:#dfe7f5;
  color:var(--primary)
}

progress::-webkit-progress-bar {
  background:#dfe7f5
}

progress::-webkit-progress-value {
  background:var(--primary)
}

progress::-moz-progress-bar {
  background:var(--primary)
}

.question-area {
  text-align:center;
  margin:28px 0 24px
}

#task-number {
  font-size:13px;
  color:var(--muted);
  margin:0 0 8px
}

#question {
  font-size:42px;
  line-height:1.15;
  font-variant-numeric:tabular-nums;
  letter-spacing:0;
  margin:0 0 12px;
  scroll-margin-top:24px
}

#instruction {
  font-size:14px;
  color:var(--muted);
  margin:0
}

.number-board {
  --columns:3;
  display:grid;
  grid-template-columns:repeat(var(--columns),minmax(0,1fr));
  gap:10px;
  max-width:480px;
  margin-inline:auto
}

.number-cell {
  position:relative;
  display:grid;
  place-items:center;
  min-width:0;
  aspect-ratio:1.25;
  font-size:30px;
  font-weight:600;
  font-variant-numeric:tabular-nums;
  background:#fff;
  border:1px solid #a6b9da;
  border-radius:8px;
  color:var(--ink);
  padding:8px;
  transition:background-color 140ms ease-out,border-color 140ms ease-out
}

.number-cell:hover:not([aria-disabled="true"]) {
  background:var(--wash);
  border-color:var(--primary)
}

.number-cell.solved {
  background:var(--primary);
  border-color:var(--primary);
  color:#fff;
  cursor:default
}

.number-cell.tried {
  background:var(--retry-wash);
  border-color:#7894c5;
  color:#2c4678;
  cursor:default
}

.number-cell svg {
  position:absolute;
  width:15px;
  height:15px;
  right:6px;
  bottom:6px
}

.number-board[data-columns="5"] .number-cell {
  font-size:24px
}

.feedback-area {
  margin-top:22px
}

#feedback {
  min-height:48px;
  font-size:15px;
  line-height:1.5;
  margin-bottom:12px;
  color:var(--primary);
  font-weight:600
}

#feedback.wrong {
  color:#304a7c
}

.round-actions {
  display:flex;
  justify-content:space-between;
  gap:12px;
  flex-wrap:wrap
}

.hint-panel {
  margin-top:24px;
  padding:18px 20px;
  background:var(--wash);
  border-radius:8px
}

.hint-panel h3 {
  margin:0 0 12px
}

.hint-panel p:last-child {
  margin-bottom:0
}

.hint-math {
  font-size:20px;
  line-height:1.7;
  font-variant-numeric:tabular-nums;
  overflow-wrap:anywhere
}

.dot-array {
  color:var(--primary);
  max-width:100%;
  height:auto;
  display:block;
  margin:16px 0
}

.results h2 {
  margin:0 0 14px
}

.result-stats {
  margin:25px 0
}

.result-stats>div {
  display:flex;
  justify-content:space-between;
  gap:16px;
  border-bottom:1px solid var(--line);
  padding:12px 0
}

.result-stats dt {
  font-size:14px
}

.result-stats dd {
  margin:0;
  font-weight:700;
  font-variant-numeric:tabular-nums;
  color:var(--primary)
}

.results h3 {
  margin:26px 0 8px
}

#review-section p {
  font-size:14px;
  color:var(--muted)
}

#review-list {
  display:flex;
  flex-wrap:wrap;
  gap:8px;
  list-style:none;
  padding:0;
  margin:14px 0 24px
}

#review-list li {
  padding:5px 10px;
  background:var(--wash);
  border-radius:5px;
  font-variant-numeric:tabular-nums
}

.result-actions {
  display:flex;
  flex-direction:column;
  gap:12px;
  align-items:stretch;
  margin-top:24px
}

.result-details {
  margin-top:30px;
  font-size:14px
}

.result-details summary {
  padding-block:10px
}

.table-wrap {
  overflow-x:auto
}

table {
  border-collapse:collapse;
  width:100%;
  margin-top:12px
}

td,th {
  padding:10px 12px;
  text-align:left;
  border-bottom:1px solid var(--line);
  font-variant-numeric:tabular-nums
}

th {
  font-size:12px;
  color:var(--muted)
}

td:first-child {
  white-space:nowrap
}

footer {
  border-top:1px solid var(--line);
  padding-block:22px 30px;
  display:flex;
  justify-content:space-between;
  gap:24px;
  color:var(--muted);
  font-size:13px
}

footer>span {
  white-space:nowrap
}

footer details p {
  max-width:65ch;
  margin-top:14px
}

#load-state {
  padding:24px 0
}

@media(max-width:800px) {
  .site-header,main,footer {
    padding-inline:22px
  }

  .workspace {
    grid-template-columns:240px minmax(0,1fr);
    gap:20px
  }

  .settings-panel {
    padding:18px
  }

  .play-area {
    padding:24px 20px
  }

  .number-board {
    gap:8px
  }

  .number-cell {
    font-size:26px
  }

  .number-board[data-columns="5"] .number-cell {
    font-size:19px
  }

  #question {
    font-size:34px
  }

  .round-progress {
    flex-wrap:wrap
  }

}

@media(max-width:650px) {
  .site-header,main,footer {
    padding-inline:18px
  }

  .site-header {
    min-height:0;
    flex-wrap:wrap;
    gap:12px;
    padding-block:16px
  }

  .language>span {
    position:absolute;
    width:1px;
    height:1px;
    overflow:hidden;
    clip-path:inset(50%)
  }

  .language select {
    font-size:14px;
    max-width:112px
  }

  .brand {
    flex-basis:100%;
    width:100%
  }

  .language {
    margin-left:auto
  }

  .page-heading {
    padding-block:26px 22px
  }

  h1 {
    font-size:29px
  }

  .page-heading p {
    font-size:15px
  }

  .workspace {
    display:flex;
    flex-direction:column;
    gap:20px;
    padding-bottom:30px
  }

  .settings-panel,.play-area {
    width:100%
  }

  .settings-panel {
    padding:18px
  }

  .settings-panel summary {
    font-size:16px;
    padding-block:2px
  }

  .operation-options {
    grid-template-columns:repeat(4,1fr)
  }

  .operation-options label>span {
    flex-direction:column;
    gap:4px;
    padding:8px 4px;
    font-size:12px
  }

  .row-options {
    grid-template-columns:repeat(6,1fr)
  }

  .play-area {
    padding:24px 18px
  }

  .welcome {
    padding:0
  }

  .welcome h2 {
    font-size:23px
  }

  .number-cell {
    font-size:28px
  }

  .number-board[data-columns="5"] .number-cell {
    font-size:20px;
    padding:3px
  }

  .number-board[data-columns="5"] .number-cell svg {
    width:10px;
    height:10px;
    right:3px;
    bottom:3px
  }

  .number-cell {
    min-height:44px
  }

  .number-board {
    gap:8px
  }

  #question {
    font-size:34px
  }

  .round-actions .primary,.round-actions .secondary {
    font-size:14px;
    padding:10px 13px
  }

  .question-area {
    margin-top:22px
  }

  footer {
    flex-direction:column;
    gap:12px
  }

  .result-stats>div {
    gap:12px
  }

}

@media(prefers-reduced-motion:reduce) {
  *,*::before,*::after {
    animation:none!important;
    transition:none!important;
    scroll-behavior:auto!important
  }

}

@media(max-width:350px) {
  .number-board {
    gap:6px
  }

}