html, body { height: 100%; overflow: hidden; }
#factoring-world { background: radial-gradient(ellipse at 64% 45%, #102434 0, #050d17 40%, #02060b 78%); }
#factoring-canvas { position: absolute; inset: 0; width: 100%; height: 100%; touch-action: none; cursor: grab; }
#factoring-canvas:active { cursor: grabbing; }
.factor-select-label { display: block; color: #9cb3c5; font-size: 9px; letter-spacing: .13em; text-transform: uppercase; margin-top: 8px; }
#factoring-panel .sfi-control-row { display: grid; grid-template-columns: 33px minmax(0, 1fr) 30px; gap: 8px; margin: 10px 0; align-items: center; }
#factoring-panel .sfi-control-row > span { font: italic 18px Georgia, serif; }
#factoring-panel output { color: #e5f6ff; text-align: right; font-variant-numeric: tabular-nums; }
.factor-equation { border-block: 1px solid #9bd8ef25; padding: 8px 0 14px; margin: 6px 0 12px; }
#equation-left, #equation-right { font: 21px/1.6 Georgia, serif; color: #ecf8ff; overflow-wrap: anywhere; }
#equation-right { color: #98daee; }
#operation-controls { display: grid; gap: 8px; }
#factoring-panel .factor-actions { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 7px; }
#factoring-panel button.factor-action { min-height: 38px; padding: 8px 6px; color: #d8f2ff; border: 1px solid #b5e7fa40; border-radius: var(--sfi-radius-control); background: #8dc7ed0b; font-size: 10px; cursor: pointer; }
#factoring-panel button.factor-action.is-primary { background: #98d9ff20; border-color: #b5e7fa80; font-size: 13px; }
#factoring-panel button.factor-action:disabled { opacity: .45; cursor: default; }
.factor-feedback { min-height: 2.8em; font-size: 11px; line-height: 1.5; color: #b7e6f5; margin: 8px 0; }
.factor-feedback:empty { display: none; }
.factor-legend { display: flex; flex-wrap: wrap; align-items: center; gap: 13px; margin: 15px 0 4px; color: #a7becd; font: 12px Georgia, serif; }
.factor-legend[hidden] { display: none; }
.factor-legend span { display: inline-flex; gap: 5px; align-items: center; }
.factor-legend i { display: inline-block; border: 1px solid currentColor; font-style: normal; }
.square-key { width: 16px; height: 16px; color: #c7aff6; background: #9e77cc50; }
.bar-key { width: 20px; height: 5px; color: #81dcef; background: #429aa650; }
.unit-key { width: 5px; height: 5px; color: #f4ce89; background: #e8b86460; }
.negative-key { width: 14px; height: 14px; line-height: 10px; text-align: center; color: #ff9ea9; background: #aa425850; }
#factoring-panel .factor-candidate-list { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 5px; margin-block: 8px; }
#factoring-panel .factor-candidate-list button { font-family: Georgia, serif; }
#factoring-panel button[aria-pressed="true"] { border-color: #a7e9ff; background: #98d9ff25; }
@media (max-width: 640px) {
  #factoring-panel .sfi-control-row { margin: 5px 0; }
  #equation-left, #equation-right { font-size: 18px; }
  .factor-equation { padding-block: 3px; margin-block: 3px 7px; }
  .factor-legend { margin-top: 7px; }
}

.factor-choices { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 6px; margin: 6px 0 13px; }
.factor-choices[data-sfi-control-count="1"] { grid-template-columns: minmax(0, 1fr); }
.factor-choices > :last-child:nth-child(odd) { grid-column: 1 / -1; }
#factoring-panel .factor-choices button { min-height: 38px; line-height: 1.3; overflow-wrap: anywhere; }
#factoring-panel #activity button { font-size: 11px; }
@media (max-width: 640px) {
  .factor-choices { gap: 4px; margin-block: 4px 8px; }
  #factoring-panel .factor-choices button { min-height: 36px; padding: 6px 4px; }
}

/* These short choice sets fit on a single row at every panel width. */
#factoring-panel #comparison { grid-template-columns: repeat(3, minmax(0, 1fr)); }
#factoring-panel #difficulty { grid-template-columns: repeat(5, minmax(0, 1fr)); }
#factoring-panel #comparison > button,
#factoring-panel #difficulty > button { grid-column: auto; }
#factoring-panel #difficulty > button { font-size: 13px; font-variant-numeric: tabular-nums; }
#collection-controls[hidden] { display: none; }

.factor-equation.is-inline { display: grid; grid-template-columns: max-content max-content; align-items: baseline; column-gap: .35em; overflow-x: auto; }
.factor-equation.is-inline > .factor-select-label { grid-column: 1 / -1; }
.factor-equation.is-inline #equation-left,
.factor-equation.is-inline #equation-right { display: inline; font-size: 17px; white-space: nowrap; overflow-wrap: normal; }

#factoring-panel #many { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 5px; }
#factoring-panel #many > button { grid-column: auto; text-align: center; padding: 10px 6px; font: 13px Georgia, serif; min-height: 48px; overflow-wrap: anywhere; }
#factoring-panel #identity { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 5px; }
#factoring-panel #identity > button { grid-column: auto; text-align: center; padding-inline: 12px; font-size: 12px; }
#factoring-volume-canvas { position: absolute; inset: 0; width: 100%; height: 100%; pointer-events: none; }

#factoring-panel #generate-multiply { display: block; width: 100%; text-align: center; font-size: 12px; line-height: 1.35; padding: 10px 12px; margin-block: 8px 12px; }

#factoring-panel #generate-multiply, #factoring-panel #generate-factor { width: 100%; box-sizing: border-box; text-align: center; padding: 12px 24px; border-radius: 16px; font-size: 12px; line-height: 1.45; white-space: normal; }
#factoring-panel .sfi-educational-note, #factoring-panel .factor-select-label { text-align: center; }

#factoring-panel #identity > button { min-height: 44px; padding: 8px 10px; }
#factoring-panel #volume-material { grid-template-columns: repeat(2, minmax(0, 1fr)); }
#factoring-panel #volume-material > button { grid-column: auto; text-align: center; padding: 10px 6px; font-size: 11px; }
#factoring-panel #generate-other { display: block; width: 100%; box-sizing: border-box; text-align: center; padding: 12px 24px; border-radius: 16px; font-size: 12px; }

.triple-formula { text-align: center; font: 19px Georgia,serif; margin: 12px 0; color: #e5f6ff; }
.triple-pair { border: 1px solid #b5e7fa25; border-radius: 12px; padding: 8px 12px; margin: 8px 0; background: #8dc7ed06; }
.triple-pair-title { text-align: center; font: 16px Georgia,serif; color: #c8e7f6; }
#factoring-panel output { text-align: center; }

#factoring-panel #factor-this { display: block; width: 100%; box-sizing: border-box; text-align: center; padding: 12px 24px; border-radius: 16px; font-size: 12px; line-height: 1.45; }
#factoring-panel #many > button { font-size: 10px; white-space: nowrap; overflow-wrap: normal; padding-inline: 4px; }

#factoring-panel .volume-spacing .sfi-control-row { grid-template-columns: minmax(0, 1fr) 34px; gap: 6px; }
#factoring-panel .volume-spacing .sfi-control-row > span { grid-column: 1 / -1; text-align: center; font: 12px/1.5 sans-serif; }

#factoring-panel .factor-equation { text-align: center; }
#factoring-panel .factor-equation.is-inline { justify-content: safe center; }

#factoring-panel .volume-spacing .sfi-control-row > span { grid-row: 1; }
#factoring-panel .volume-spacing input { grid-column: 1; grid-row: 2; }
#factoring-panel .volume-spacing output { grid-column: 2; grid-row: 2; }

#factor-feedback.is-correct { text-align: center; color: #c3f4e5; padding: 12px; border: 1px solid #b0e9d655; border-radius: 10px; background: #9cdec415; font-size: 14px; }

#factoring-panel #volume-material { grid-template-columns: repeat(6,minmax(0,1fr)); }
#factoring-panel #volume-material > button { grid-column: span 2; }
#factoring-panel #volume-material > button:nth-child(n+4) { grid-column: span 3; }

#factoring-panel #volume-material { grid-template-columns: repeat(2,minmax(0,1fr)); }
#factoring-panel #volume-material > button, #factoring-panel #volume-material > button:nth-child(n+4) { grid-column: auto; }

#factoring-panel .triple-pair .sfi-control-row > span, #factoring-panel .triple-pair .sfi-control-row > output { font-size: 12px; }