* {
  box-sizing: border-box;
}

button,
input {
  font: inherit;
}

button {
  touch-action: manipulation;
}

[hidden] {
  display: none !important;
}

.section-heading {
  margin-bottom: 16px;
}

.section-kicker {
  margin: 0 0 5px;
  color: var(--kw-accent);
  font-size: 0.78rem;
  font-weight: 780;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

h2,
h3 {
  color: var(--kw-ink);
}

h2 {
  margin: 0;
  font-size: clamp(1.18rem, 2vw, 1.48rem);
  line-height: 1.38;
}

h3 {
  margin: 0;
  font-size: 0.96rem;
  line-height: 1.45;
}

.tool-shell {
  display: grid;
  grid-template-columns: minmax(0, 0.94fr) minmax(0, 1.06fr);
  border: 1px solid var(--kw-line-strong);
  background: var(--kw-surface);
}

.calculator-panel,
.visual-panel {
  min-width: 0;
  padding: 24px;
}

.calculator-panel {
  border-right: 1px solid var(--kw-line);
}

.input-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px;
}

.input-row {
  min-width: 0;
}

.input-row-wide {
  grid-column: 1 / -1;
}

.input-row label {
  display: block;
  margin-bottom: 5px;
  font-weight: 730;
  line-height: 1.45;
}

.input-wrap {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: stretch;
}

.input-wrap input {
  width: 100%;
  min-width: 0;
  border: 1px solid var(--kw-line-strong);
  border-radius: 0;
  padding: 10px 11px;
  background: var(--kw-surface);
  color: var(--kw-ink);
  font-variant-numeric: tabular-nums;
}

.input-wrap input[aria-invalid="true"] {
  border-color: #9b2f2f;
  background: #fff8f8;
}

.unit {
  min-width: 58px;
  display: grid;
  place-items: center;
  border: 1px solid var(--kw-line-strong);
  border-left: 0;
  padding: 0 9px;
  background: var(--kw-paper);
  color: var(--kw-muted);
  font-size: 0.86rem;
  font-weight: 730;
}

.unit-plain {
  min-width: 48px;
}

.field-help,
.field-error {
  min-height: 1.3em;
  margin: 4px 0 0;
  font-size: 0.78rem;
  line-height: 1.45;
}

.field-help {
  color: var(--kw-muted);
}

.field-error {
  color: #842929;
  font-weight: 650;
}

.direction-note {
  margin: 16px 0 0;
  padding: 9px 11px;
  border-left: 3px solid var(--kw-line-strong);
  background: var(--kw-paper);
  color: var(--kw-muted);
  font-size: 0.84rem;
}

.form-error {
  margin: 12px 0 0;
  padding: 9px 11px;
  border-left: 4px solid #9b2f2f;
  background: #f8e9e7;
  color: #762525;
  font-weight: 650;
}

.form-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 17px;
}

.button {
  min-height: 42px;
  border: 1px solid var(--kw-accent);
  border-radius: 2px;
  padding: 8px 15px;
  cursor: pointer;
  font-weight: 760;
}

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

.button-primary:hover {
  background: #1b4738;
}

.button-secondary {
  background: var(--kw-surface);
  color: var(--kw-accent);
}

.button:hover {
  border-color: var(--kw-ink);
}

.button:focus-visible,
.input-wrap input:focus-visible {
  outline: 3px solid var(--kw-accent);
  outline-offset: 3px;
}

.result-box {
  margin-top: 20px;
  border: 1px solid var(--kw-line-strong);
  border-left: 4px solid var(--kw-line-strong);
  padding: 16px;
  background: var(--kw-paper);
}

.result-box[data-state="complete"] {
  border-left-color: var(--kw-accent);
  background: var(--kw-accent-soft);
}

.result-box[data-state="warning"] {
  border-left-color: #a7642a;
  background: #fbf2e7;
}

.result-heading-row,
.visual-heading-row {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 12px;
}

.result-label {
  margin: 0 0 2px;
  color: var(--kw-accent);
  font-size: 0.78rem;
  font-weight: 780;
}

.status-badge {
  flex: 0 0 auto;
  border: 1px solid var(--kw-line-strong);
  padding: 3px 8px;
  background: var(--kw-paper);
  color: var(--kw-muted);
  font-size: 0.74rem;
  font-weight: 760;
  line-height: 1.5;
}

.status-badge[data-state="complete"] {
  border-color: var(--kw-accent);
  background: var(--kw-accent-soft);
  color: var(--kw-accent);
}

.status-badge[data-state="warning"] {
  border-color: #a7642a;
  background: #fbf2e7;
  color: #78451c;
}

.collision-warning {
  margin: 13px 0 0;
  padding: 9px 11px;
  border: 1px solid #c78b55;
  background: #fff8ef;
  color: #6e3d16;
  font-size: 0.84rem;
  font-weight: 650;
}

.primary-results,
.detail-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  margin: 14px 0 0;
  border-top: 1px solid var(--kw-line);
  border-left: 1px solid var(--kw-line);
}

.primary-results > div,
.detail-grid > div {
  min-width: 0;
  border-right: 1px solid var(--kw-line);
  border-bottom: 1px solid var(--kw-line);
  padding: 9px 10px;
  background: rgba(251, 250, 246, 0.72);
}

.primary-results > div:first-child {
  grid-column: 1 / -1;
}

.primary-results dt,
.detail-grid dt {
  color: var(--kw-muted);
  font-size: 0.74rem;
  font-weight: 700;
  line-height: 1.4;
}

.primary-results dd,
.detail-grid dd {
  margin: 3px 0 0;
  color: var(--kw-ink);
  font-size: 0.9rem;
  font-weight: 760;
  font-variant-numeric: tabular-nums;
  line-height: 1.4;
  overflow-wrap: anywhere;
}

.result-group {
  margin-top: 16px;
}

.result-group h3 {
  color: var(--kw-accent);
  font-size: 0.84rem;
}

.visual-panel {
  display: grid;
  align-content: start;
  gap: 16px;
}

.diagram-figure,
.energy-chart {
  min-width: 0;
  margin: 0;
  border: 1px solid var(--kw-line);
  padding: 12px;
  background: var(--kw-paper);
}

.diagram-figure svg {
  display: block;
  width: 100%;
  height: auto;
}

.diagram-figure figcaption,
.energy-chart > p {
  margin: 8px 0 0;
  color: var(--kw-muted);
  font-size: 0.77rem;
  line-height: 1.55;
}

.track-line {
  stroke: var(--kw-line-strong);
  stroke-width: 2;
}

.row-label,
.velocity-label,
.diagram-direction,
.momentum-sign,
.bar-row-label,
.bar-value {
  fill: var(--kw-muted);
  font-family: var(--kw-font);
}

.row-label {
  font-size: 15px;
  font-weight: 760;
}

.object {
  stroke-width: 2;
}

.object-1 {
  fill: #dce9ee;
  stroke: #33677d;
}

.object-2 {
  fill: #f2e3d4;
  stroke: #a7642a;
}

.object-label {
  fill: var(--kw-ink);
  font-family: var(--kw-font);
  font-size: 13px;
  font-weight: 760;
}

.velocity-arrow {
  stroke-width: 4;
}

.velocity-arrow.is-zero {
  display: none;
}

.object-1-line {
  stroke: #33677d;
}

.object-2-line {
  stroke: #a7642a;
}

#velocity-arrow-1 path {
  fill: #33677d;
}

#velocity-arrow-2 path {
  fill: #a7642a;
}

.velocity-label {
  font-size: 13px;
  font-weight: 700;
}

.diagram-direction {
  font-size: 12px;
}

.momentum-figure h3,
.energy-chart h3 {
  margin-bottom: 8px;
  color: var(--kw-accent);
}

.momentum-axis {
  stroke: var(--kw-ink);
  stroke-width: 1.5;
}

.chart-separator {
  stroke: var(--kw-line);
  stroke-width: 1;
  stroke-dasharray: 5 5;
}

.momentum-bar {
  stroke-width: 1;
}

.momentum-sign,
.bar-row-label,
.bar-value {
  font-size: 12px;
}

.bar-row-label {
  font-weight: 720;
}

.bar-value {
  fill: var(--kw-ink);
  font-variant-numeric: tabular-nums;
}

.energy-chart {
  display: grid;
  gap: 10px;
}

.energy-row {
  display: grid;
  grid-template-columns: 72px minmax(0, 1fr) minmax(86px, auto);
  align-items: center;
  gap: 9px;
  min-width: 0;
}

.energy-row > span {
  color: var(--kw-muted);
  font-size: 0.78rem;
  font-weight: 720;
}

.energy-row > strong {
  min-width: 0;
  color: var(--kw-ink);
  font-size: 0.8rem;
  font-variant-numeric: tabular-nums;
  overflow-wrap: anywhere;
}

.energy-track {
  height: 16px;
  overflow: hidden;
  border: 1px solid var(--kw-line-strong);
  background: var(--kw-surface);
}

.energy-track i {
  display: block;
  width: 0;
  height: 100%;
  background: var(--kw-accent);
}

.energy-loss-row .energy-track i {
  background: #a7642a;
}

.content-section {
  margin-top: 30px;
  border-top: 1px solid var(--kw-line-strong);
  padding-top: 25px;
}

.steps-list {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  margin: 0;
  padding: 0;
  border-block: 1px solid var(--kw-line);
  list-style: none;
  counter-reset: steps;
}

.steps-list li {
  position: relative;
  min-width: 0;
  border-right: 1px solid var(--kw-line);
  padding: 35px 12px 13px;
  counter-increment: steps;
  color: var(--kw-muted);
  font-size: 0.86rem;
  overflow-wrap: anywhere;
}

.steps-list li:last-child {
  border-right: 0;
}

.steps-list li::before {
  content: counter(steps, decimal-leading-zero);
  position: absolute;
  top: 7px;
  left: 12px;
  color: var(--kw-accent);
  font-size: 0.75rem;
  font-weight: 800;
}

.formula-list {
  display: grid;
  gap: 0;
  border-top: 1px solid var(--kw-line);
}

.formula-list article {
  display: grid;
  grid-template-columns: minmax(260px, 1.18fr) minmax(0, 0.82fr);
  min-width: 0;
  border-bottom: 1px solid var(--kw-line);
  padding: 12px 0;
}

.formula-list strong,
.formula-list span {
  min-width: 0;
  overflow-wrap: anywhere;
}

.formula-list strong {
  padding-right: 16px;
  color: var(--kw-ink);
  font-size: 0.9rem;
  font-weight: 720;
}

.formula-list span {
  border-left: 1px solid var(--kw-line);
  padding-left: 16px;
  color: var(--kw-muted);
  font-size: 0.84rem;
}

.notes-list {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  margin: 0;
  padding: 0;
  border-top: 1px solid var(--kw-line);
  border-left: 1px solid var(--kw-line);
  list-style: none;
}

.notes-list li {
  min-width: 0;
  border-right: 1px solid var(--kw-line);
  border-bottom: 1px solid var(--kw-line);
  padding: 11px 13px 11px 30px;
  color: var(--kw-muted);
  font-size: 0.84rem;
  overflow-wrap: anywhere;
}

.notes-list li::before {
  content: "—";
  margin-left: -17px;
  margin-right: 7px;
  color: var(--kw-accent);
}

@media (max-width: 980px) {
  .tool-shell {
    grid-template-columns: 1fr;
  }

  .calculator-panel {
    border-right: 0;
    border-bottom: 1px solid var(--kw-line);
  }
}

@media (max-width: 700px) {
  .calculator-panel,
  .visual-panel {
    padding: 18px;
  }

  .input-grid,
  .primary-results,
  .detail-grid,
  .notes-list {
    grid-template-columns: 1fr;
  }

  .input-row-wide,
  .primary-results > div:first-child {
    grid-column: auto;
  }

  .steps-list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .steps-list li:nth-child(2) {
    border-right: 0;
  }

  .steps-list li:nth-child(-n + 2) {
    border-bottom: 1px solid var(--kw-line);
  }

  .formula-list article {
    grid-template-columns: 1fr;
    gap: 7px;
  }

  .formula-list strong {
    padding-right: 0;
  }

  .formula-list span {
    border-left: 0;
    padding-left: 0;
  }
}

@media (max-width: 430px) {
  .calculator-panel,
  .visual-panel {
    padding: 15px;
  }

  .result-heading-row,
  .visual-heading-row {
    align-items: stretch;
    flex-direction: column;
  }

  .status-badge {
    align-self: flex-start;
  }

  .form-actions {
    display: grid;
    grid-template-columns: 1fr;
  }

  .form-actions .button {
    width: 100%;
  }

  .steps-list {
    grid-template-columns: 1fr;
  }

  .steps-list li,
  .steps-list li:nth-child(2) {
    border-right: 0;
    border-bottom: 1px solid var(--kw-line);
  }

  .steps-list li:last-child {
    border-bottom: 0;
  }

  .energy-row {
    grid-template-columns: 62px minmax(0, 1fr);
  }

  .energy-row > strong {
    grid-column: 2;
  }

  .diagram-figure,
  .energy-chart {
    padding: 9px;
  }
}