.site-header {
  background: var(--colour-header);
  color: var(--colour-header-text);
  border-bottom: 0.2rem solid var(--colour-accent);
  padding: var(--space-sm) var(--space-lg);
}

.site-header__inner,
.site-main,
.site-footer__inner {
  width: min(100%, var(--width-page));
  margin-inline: auto;
}

body:has(.site-main--calculator) :is(.site-header__inner, .site-main, .site-footer__inner) {
  width: min(100%, 89rem);
}

.site-header__inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-sm) var(--space-md);
}

.site-header__brand {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  min-height: var(--touch-min);
  color: var(--colour-header-text);
  text-decoration: none;
}

.site-header__brand:hover,
.site-header__brand:focus-visible {
  color: var(--colour-header-text);
}

.site-header__logo {
  display: block;
  height: var(--logo-height-mobile);
  width: auto;
  max-width: none;
  flex: 0 0 auto;
}

.site-header__product {
  font-size: 0.95rem;
  font-weight: 650;
  letter-spacing: 0.02em;
  line-height: 1.2;
}

.site-nav a {
  color: var(--colour-header-text);
  text-decoration: none;
  min-height: var(--touch-min);
  display: inline-flex;
  align-items: center;
  padding-inline: var(--space-xs);
  font-weight: 650;
}

.site-nav a:hover,
.site-nav a:focus-visible {
  color: var(--colour-accent);
}

.site-nav a[aria-current="page"] {
  color: var(--colour-accent);
  text-decoration: underline;
  text-underline-offset: 0.3rem;
}

.site-main {
  padding: var(--space-lg);
}

.hero {
  display: grid;
  gap: var(--space-sm);
  max-width: 42rem;
}

.hero__tagline {
  font-size: 1.1rem;
  max-width: 36rem;
}

.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-xs);
  align-items: center;
  font-size: 0.95rem;
  margin-bottom: var(--space-md);
}

.breadcrumb a {
  min-height: var(--touch-min);
  display: inline-flex;
  align-items: center;
}

.tool-intro {
  display: grid;
  gap: var(--space-sm);
  max-width: 46rem;
  margin-bottom: var(--space-lg);
}

.tool-workspace {
  display: grid;
  gap: var(--space-lg);
  align-items: start;
}

.tool-workspace > * {
  min-width: 0;
}

@media screen and (min-width: 60rem) {
  .tool-workspace {
    grid-template-columns: minmax(20rem, 26rem) minmax(0, 1fr);
    grid-template-areas:
      "inputs schematic"
      "results results";
    /* Both cards fill the first row. A fixed schematic height left the
       page background beside the lower inputs and delayed Results. */
    align-items: stretch;
  }

  #spur-gear-form {
    grid-area: inputs;
  }

  .tool-workspace > .diagram-panel {
    grid-area: schematic;
    grid-template-columns: minmax(0, 1fr);
    grid-template-rows: auto auto auto auto auto auto auto;
    align-content: start;
    gap: 0.65rem;
    padding: var(--space-sm) var(--space-md);
    height: auto;
    max-height: none;
  }

  .tool-workspace > .diagram-panel:has(> .diagram-stage:not([hidden])) {
    grid-template-rows: auto auto auto minmax(9rem, 1fr) auto auto auto;
  }

  .tool-workspace > .diagram-panel > h2 {
    grid-row: 1;
  }

  .tool-workspace > .diagram-panel > .diagram-view {
    grid-row: 2;
  }

  .tool-workspace > .diagram-panel > #diagram-unavailable {
    grid-row: 3;
    align-self: start;
    height: auto;
  }

  .tool-workspace > .diagram-panel > #diagram-notice,
  .tool-workspace > .diagram-panel > #outline-status {
    align-self: start;
    height: auto;
  }

  .tool-workspace > .diagram-panel > .diagram-stage {
    grid-row: 4;
    min-width: 0;
    min-height: 9rem;
  }

  .tool-workspace > .diagram-panel > #diagram-notice {
    grid-row: 5;
  }

  .tool-workspace > .diagram-panel > #outline-status {
    grid-row: 6;
  }

  .tool-workspace > .diagram-panel > .diagram-overlays {
    grid-row: 7;
  }

  .tool-workspace > .diagram-panel:has(> .diagram-stage:not([hidden])):has(> .feature-identify:not([hidden])) {
    grid-template-rows: auto auto auto minmax(9rem, 1fr) auto auto auto auto;
  }

  .tool-workspace > .diagram-panel > .feature-identify:not([hidden]) {
    grid-row: 5;
    align-self: start;
  }

  .tool-workspace > .diagram-panel:has(> .feature-identify:not([hidden])) > #diagram-notice {
    grid-row: 6;
  }

  .tool-workspace > .diagram-panel:has(> .feature-identify:not([hidden])) > #outline-status {
    grid-row: 7;
  }

  .tool-workspace > .diagram-panel:has(> .feature-identify:not([hidden])) > .diagram-overlays {
    grid-row: 8;
  }

  .tool-workspace > .diagram-panel .diagram-stage > .diagram-svg {
    width: 100%;
    height: 100%;
    min-height: 9rem;
    max-height: none;
    aspect-ratio: auto;
  }

  .diagram-panel--tooth .diagram-stage {
    display: flex;
    flex-direction: column;
    align-items: stretch;
    justify-content: flex-start;
  }

  .diagram-panel--tooth #gear-outline {
    display: none;
  }

  .tool-workspace > .diagram-panel.diagram-panel--tooth .diagram-stage #tooth-profile {
    width: min(100%, 36rem, 68vh);
    height: auto;
    aspect-ratio: 1;
    min-height: 0;
    max-height: none;
    align-self: center;
  }

  .tool-workspace > .results-panel {
    grid-area: results;
    width: 100%;
    justify-self: stretch;
  }

  .results-panel .result-group {
    grid-template-columns: repeat(3, minmax(0, 1fr));
    column-gap: var(--space-lg);
    align-items: start;
  }

  .results-panel .result-group > :is(h2, p, .result-actions) {
    grid-column: 1 / -1;
  }

  .results-panel .result-group > h3:nth-of-type(1) {
    grid-column: 1;
    grid-row: 4;
  }

  .results-panel .result-group > dl:nth-of-type(1) {
    grid-column: 1;
    grid-row: 5;
  }

  .results-panel .result-group > h3:nth-of-type(2) {
    grid-column: 2;
    grid-row: 4;
  }

  .results-panel .result-group > dl:nth-of-type(2) {
    grid-column: 2;
    grid-row: 5;
  }

  .results-panel .result-group > h3:nth-of-type(3) {
    grid-column: 3;
    grid-row: 4;
  }

  .results-panel .result-group > dl:nth-of-type(3) {
    grid-column: 3;
    grid-row: 5;
  }
}

.understand-panel {
  margin-top: var(--space-lg);
}

.site-footer {
  padding: var(--space-lg);
  border-top: 1px solid var(--colour-border);
}

.site-footer__inner {
  font-size: 0.9rem;
}

@media (min-width: 45rem) {
  .site-header {
    padding: var(--space-md) var(--space-lg);
  }

  .site-header__inner {
    flex-wrap: nowrap;
  }

  .site-header__logo {
    height: var(--logo-height);
  }

  .site-header__product {
    font-size: 1.05rem;
  }

  .site-main {
    padding: var(--space-xl) var(--space-lg);
  }

  .site-main--calculator {
    padding-top: var(--space-lg);
  }

  .site-main--calculator .tool-intro {
    margin-bottom: var(--space-md);
  }
}