.out-activity, .operation-activity, .product-activity {
  margin: 1.5rem 0 2.2rem;
  padding: 1.4rem 1.6rem;
  border: 2px solid rgba(57,58,59,.55);
  border-radius: 5px 12px 7px 10px;
  background: #ffffff;
  box-shadow: 5px 5px 0 rgba(22,212,209,.28);
}
.out-activity.solved, .operation-activity.solved, .product-activity.solved {
  border-color: var(--turquoise-dark);
}
.operation-source {
  margin: 1.1rem 0 .8rem;
  font-size: clamp(1.6rem, 3.5vw, 2.35rem);
  line-height: 1.3;
  font-variant-numeric: tabular-nums;
}
.operation-source sup, .operation-number sup, .product-equation sup {
  font-size: .58em;
}
.out-equation-scroll {
  overflow-x: auto;
  padding: .35rem .3rem .5rem;
}
.out-equation {
  position: relative;
  width: max-content;
  min-height: 9rem;
}
.out-number-board {
  position: relative;
  width: max-content;
  min-height: 8.5rem;
  padding-right: 7rem;
}
.out-digit-line {
  display: flex;
  align-items: stretch;
  width: max-content;
}
.out-digit {
  font-size: clamp(2.6rem, 6vw, 4.1rem);
  line-height: 1.3;
  font-variant-numeric: tabular-nums;
}
.out-digit.pending-zero { visibility: hidden; }
.out-gap {
  flex: 0 0 .65rem;
  width: .65rem;
  min-height: 5.8rem;
  padding: 0;
  border: 0;
  border-bottom: 3px solid transparent;
  background: transparent;
  cursor: pointer;
}
.out-gap:hover:not(:disabled), .out-gap:focus-visible {
  border-bottom-color: var(--turquoise);
}
.out-gap:disabled { cursor: default; }
.out-decimal {
  top: 3rem;
  width: 1.2rem;
  height: 1.2rem;
}
.out-power {
  position: absolute;
  top: .55rem;
  z-index: 2;
  width: max-content;
  font-size: clamp(1.65rem, 3vw, 2.3rem);
  font-variant-numeric: tabular-nums;
  pointer-events: none;
}
.out-power[hidden] { display: none; }
.out-power sup { font-size: .58em; }
.out-count { margin-top: .1rem; }
.out-answer { margin-top: .6rem; }.calculation-subheading { margin-top: 3rem !important; }
.operation-source span { margin: 0 .3rem; }
.operation-row {
  display: flex;
  align-items: center;
  gap: .5rem;
  max-width: 40rem;
  margin: .6rem 0;
}
.operation-symbol {
  width: 1.6rem;
  flex: 0 0 1.6rem;
  font-size: 2rem;
  text-align: center;
}
.operation-rail {
  position: relative;
  width: 100%;
  min-width: 26rem;
  height: 6.4rem;
}
.operation-rail-line {
  position: absolute;
  top: 4.65rem;
  left: 5rem;
  right: 5rem;
  border-top: 2px solid rgba(57,58,59,.4);
}
.operation-moving {
  position: absolute;
  z-index: 2;
  top: .35rem;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 10.5rem;
  min-height: 3.25rem;
  padding: .3rem .45rem;
  transform: translateX(-50%);
  border: 2px solid var(--ink);
  border-radius: 5px 9px 5px 7px;
  background: #ffffff;
  box-shadow: 3px 3px 0 var(--turquoise);
  cursor: grab;
  touch-action: none;
  user-select: none;
}
.operation-moving:active { cursor: grabbing; }
.operation-moving:focus-visible { outline: 3px solid var(--turquoise); outline-offset: 3px; }
.operation-number {
  white-space: nowrap;
  font-size: clamp(1.2rem, 2.3vw, 1.6rem);
  font-variant-numeric: tabular-nums;
}
.operation-range {
  position: absolute;
  top: 4.15rem;
  left: 5rem;
  width: calc(100% - 10rem);
  height: 1.15rem;
  margin: 0;
  opacity: .15;
  accent-color: #16D4D1;
  cursor: ew-resize;
}
.operation-range:focus-visible { opacity: 1; outline: 3px solid var(--turquoise); }
.operation-status { min-height: 1.5rem; margin: .2rem 0 .75rem; color: var(--turquoise-dark); font-weight: 700; }
.operation-calculate:disabled { opacity: .45; cursor: default; }
.operation-answer { line-height: 1.5; }
.operation-answer strong { color: var(--turquoise-dark); }
.operation-rule-line { margin: .8rem 0; font-size: clamp(1.15rem, 2.1vw, 1.45rem); line-height: 2.25; }
.operation-rule-slot, .product-slot {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 6.6rem;
  min-height: 2.6rem;
  margin: 0 .2rem;
  padding: .1rem .4rem;
  vertical-align: middle;
  border: 0;
  border-bottom: 3px solid var(--ink);
  border-radius: 0;
  background: #ffffff;
  color: var(--ink);
  font: 700 1.1rem "Lato", sans-serif;
  cursor: pointer;
}
.operation-rule-slot.filled, .product-slot.filled { border-bottom-color: var(--turquoise-dark); cursor: default; }
.operation-rule-slot.incorrect, .product-slot.incorrect { border-bottom-color: #bf2f39; background: #ffe1e3; color: #8b1e27; }
.operation-rule-bank {
  display: flex;
  flex-wrap: wrap;
  gap: .8rem;
  margin: 1.1rem 0 2rem;
}
.operation-rule-token {
  flex: 0 0 7.25rem;
  width: 7.25rem;
  min-width: 7.25rem;
  height: 3.05rem;
  min-height: 3.05rem;
  padding: 0 0 .35rem;
  border: 0;
  border-radius: 0;
  background-color: #ffffff;
  background-image: url("./start-button-BVNEoHc_.png");
  background-position: center;
  background-size: 125% 214%;
  background-repeat: no-repeat;
  box-shadow: 4px 4px 0 var(--turquoise);
  color: var(--ink);
  font: 400 1rem/1 "KG Thinking Out Loud", "Comic Sans MS", cursive;
  cursor: grab;
  touch-action: manipulation;
  transform: rotate(-.5deg);
}
.operation-rule-token:hover:not(:disabled) { transform: translate(2px, 2px) rotate(-.5deg); box-shadow: 2px 2px 0 var(--turquoise); }
.operation-rule-token:active { cursor: grabbing; }
.operation-rule-token.selected { outline: 3px solid var(--turquoise); outline-offset: 3px; }
.operation-rule-token.placed { opacity: .4; cursor: default; }
.operation-rule-token.incorrect {
  background-color: #ffffff;
  background-image: url("./start-button-BVNEoHc_.png");
  box-shadow: 4px 4px 0 #bf2f39;
  outline: 3px solid #bf2f39;
  color: #8b1e27;
}
.product-source-token {
  display: inline-block;
  padding: .03em .2em .08em;
  border: 1px solid var(--ink);
  border-radius: 6px;
  background: #ffffff;
  box-shadow: 3px 3px 0 var(--turquoise);
  color: inherit;
  font: inherit;
  line-height: 1;
  vertical-align: baseline;
  cursor: grab;
  touch-action: manipulation;
}
.product-source-token:hover:not(:disabled) { transform: translate(1px, 1px); box-shadow: 2px 2px 0 var(--turquoise); }
.product-source-token.selected { outline: 2px solid var(--turquoise); outline-offset: 2px; }
.product-source-token.placed { border-color: transparent; background: transparent; box-shadow: none; color: transparent; opacity: 1; cursor: default; }
.product-source-token.incorrect { border-color: #bf2f39; background: #ffe1e3; box-shadow: 3px 3px 0 #bf2f39; color: #8b1e27; }
.product-equation {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: .25rem .7rem;
  margin: 1.2rem 0;
  font-size: clamp(2rem, 4vw, 3rem);
  font-variant-numeric: tabular-nums;
}
.product-coefficient-group, .product-ten-group { display: inline-flex; align-items: baseline; white-space: nowrap; }
.product-operation-sign { margin: 0 .2rem; }
.product-exponent-group { position: relative; top: -1.5rem; display: inline-flex; align-items: center; font-size: .58em; line-height: 1; }
.product-equation .product-slot { min-width: 4.4rem; min-height: 2.7rem; margin: 0 .08rem; font-size: 1.3rem; }
.product-equation .product-slot.exponent-slot { min-width: 3rem; min-height: 2.15rem; font-size: 1.1rem; }
.product-actions { display: flex; justify-content: flex-end; }
.product-actions .product-calculate { margin: .2rem 0 .6rem; }
.product-answer { margin-top: .5rem; line-height: 1.4; }
.product-result[hidden] { display: none; }
.product-normalize-prompt { margin: .5rem 0 .8rem; font-size: 1.15rem; }
.product-result-board { padding-right: 8rem; }
.product-result-board .decimal-chip { top: 3.1rem; width: 1.2rem; height: 1.2rem; }
.product-result-power { position: absolute; top: 0; width: max-content; font-size: clamp(2.6rem, 7vw, 4.4rem); line-height: 1.3; font-variant-numeric: tabular-nums; pointer-events: none; }
.product-result-power sup { font-size: .58em; }
.product-result-count { margin: .2rem 0 0; }
.product-result-board .digit.pending-zero { visibility: hidden; }
.operation-normalize { width: min(100%, 44rem); margin: 1rem auto 0; padding: 1rem 0 0; border-top: 2px solid #dcebf0; }
.operation-normalize, .operation-normalize-answer { --normalization-font-size: clamp(1.9rem, 4vw, 2.7rem); }
.operation-normalize .digit, .operation-normalize .product-result-power, .operation-normalize-answer { font-size: var(--normalization-font-size); }
.operation-normalize .product-result-chip { top: 1.9rem; }
.operation-normalize-answer { margin: .6rem auto 0; }
@media (max-width: 760px) {
  .product-result-board .decimal-chip { top: 1.9rem; }
  .product-result-power { font-size: 2rem; }
  .operation-normalize .product-result-chip { top: 1.55rem; }
}
@media (max-width: 760px) {
  .out-activity, .operation-activity, .product-activity { padding: 1rem; }
  .operation-rail { min-width: 0; flex: 1; }
  .operation-moving { width: 9.5rem; }
  .operation-number { font-size: 1.1rem; }
  .operation-source { overflow-wrap: anywhere; }
}
/* Addition and subtraction follow the two-column setup and solve layout. */
.operation-activity .activity-top { justify-content: center; margin-bottom: .3rem; }
.operation-workspace {
  display: grid;
  grid-template-columns: minmax(14rem, 1fr) minmax(19rem, 1fr);
  width: min(100%, 44rem);
  margin: 1.3rem auto 0;
}
.operation-traditional {
  min-width: 0;
  padding: 0 1.2rem 1rem;
}
.operation-solve {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  grid-template-rows: auto auto auto;
  min-width: 0;
  padding: 0 1.2rem 0 1.8rem;
  border-left: 2px solid #dcebf0;
}
.operation-column-label {
  width: min(100%, 11rem);
  margin: 0 auto 1rem;
  padding: .35rem .5rem;
  border-radius: 9px;
  background: #dff5f9;
  color: var(--ink);
  font: 400 1rem/1.2 "KG Thinking Out Loud", "Comic Sans MS", cursive;
  text-align: center;
}
.operation-fixed-stack {
  width: fit-content;
  margin: 2rem auto 0;
  padding: 0 .5rem .35rem 0;
  border-bottom: 2px solid var(--ink);
}
.operation-fixed-row {
  display: flex;
  align-items: center;
  min-height: 2.75rem;
  white-space: nowrap;
  font-size: clamp(1.55rem, 2.5vw, 2rem);
  font-variant-numeric: tabular-nums;
}
.operation-fixed-row sup { font-size: .58em; }
.operation-fixed-symbol {
  flex: 0 0 1.7rem;
  width: 1.7rem;
  text-align: center;
}
.operation-solve .operation-column-label { grid-column: 1; grid-row: 1; }
.operation-rows { min-width: 0; }
.operation-solve .operation-rows { grid-column: 1; grid-row: 2; }
.operation-activity .operation-row { max-width: none; height: 4.6rem; margin: 0; }
.operation-activity .operation-rail { min-width: 0; height: 4.6rem; --rail-inset: 4rem; }
.operation-activity .operation-rail-line {
  top: 2.9rem;
  left: var(--rail-inset);
  right: var(--rail-inset);
}
.operation-activity .operation-moving {
  top: 0;
  width: 7.8rem;
  min-height: 2.45rem;
  padding: .15rem .35rem;
}
.operation-activity .operation-number { font-size: clamp(1rem, 1.8vw, 1.3rem); }
.operation-activity .operation-range {
  top: 2.48rem;
  left: var(--rail-inset);
  width: calc(100% - 2 * var(--rail-inset));
}
.operation-calculate {
  grid-column: 1;
  grid-row: 3;
  justify-self: end;
  align-self: center;
  width: 7.25rem;
  min-height: 3.05rem;
  margin-top: 0;
  margin-right: -3.75rem;
  padding: 0 0 .35rem;
  border: 0;
  border-radius: 0;
  background-color: #ffffff;
  background-image:
    linear-gradient(to left, var(--turquoise) 1px, transparent 1px),
    linear-gradient(to top, var(--turquoise) 1px, transparent 1px),
    url("./start-button-BVNEoHc_.png");
  background-position: center, center, center calc(50% + 1px);
  background-size: 100% 100%, 100% 100%, 128% auto;
  background-repeat: no-repeat;
  box-shadow: 4px 4px 0 var(--turquoise);
  color: var(--ink);
  font: 400 1rem/1 "KG Thinking Out Loud", "Comic Sans MS", cursive;
  transform: rotate(-.5deg);
}
.operation-calculate:hover:not(:disabled) {
  box-shadow: 2px 2px 0 var(--turquoise);
  filter: none;
}
.operation-activity .operation-status {
  margin: 1rem auto .3rem;
  color: var(--ink);
  font-size: .94rem;
  text-align: center;
}
.operation-solve .operation-answer {
  grid-column: 1;
  grid-row: 3;
  justify-self: center;
  align-self: center;
  margin: 0;
  background: none;
  font-size: 1.4rem;
  font-weight: 400;
  line-height: 1.25;
  text-align: center;
}
@media (max-width: 980px) {
  .operation-calculate { align-self: flex-end; margin-top: .15rem; margin-right: 0; }
  .operation-workspace { grid-template-columns: minmax(0, 1fr); }
  .operation-traditional { padding-bottom: 1.2rem; }
  .operation-fixed-stack { margin-top: .5rem; }
  .operation-solve {
    display: flex;
    flex-direction: column;
    padding: 1rem .8rem 0;
    border-left: 0;
    border-top: 2px solid #dcebf0;
  }
  .operation-solve .operation-answer { margin: .75rem auto 0; }
}
@media (max-width: 760px) {
  .operation-activity .activity-top { justify-content: flex-start; }
  .operation-fixed-row { font-size: 1.45rem; }
  .operation-activity .operation-row { height: 4.5rem; }
  .operation-activity .operation-rail { height: 4.5rem; }
  .operation-activity .operation-number { font-size: 1.05rem; }
}
/* Match every movable decimal to the Practice 5 and 6 chip. */
.decimal-activity .decimal-chip {
  top: 3.1rem;
  width: 1.2rem;
  height: 1.2rem;
}
@media (max-width: 760px) {
  .decimal-activity .loop-board .decimal-chip { top: 1.9rem; }
}

.direction-cue.yellow { background: #f2dd00; }