.page {
  height: calc(100vh - 48px);
  max-height: calc(100vh - 48px);
  display: grid;
  grid-template-rows: auto auto 1fr auto;
  gap: 10px;
  max-width: none;
  width: min(1920px, calc(100vw - 48px));
  margin: 8px auto;
  padding: 14px;
  background: var(--shell-bg);
  border: 2px solid var(--shell-border);
  border-radius: 28px;
  box-shadow: 0 24px 60px rgba(46, 40, 32, 0.12);
  animation: shellLift 0.6s ease-out both;
}

.site-header {
  background: transparent;
  color: var(--header-text);
  display: grid;
  place-items: center;
  padding: 4px 24px 0;
  border-radius: 0;
  border: none;
  box-shadow: none;
  font-size: 28px;
  font-weight: 600;
  font-family: var(--font-display);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  animation: headerSlide 0.5s ease-out both;
}

.top-nav {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 2px 12px 0;
  flex-wrap: wrap;
  background: transparent;
  border: none;
  border-radius: 0;
  box-shadow: none;
  animation: headerSlide 0.55s ease-out both;
}

.top-nav button {
  background: var(--cosmic-black);
  border: 1px solid var(--cosmic-black);
  color: #ffffff;
  padding: 8px 18px;
  border-radius: 10px;
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  white-space: nowrap;
  flex-shrink: 0;
  min-height: 38px;
  line-height: 1.4;
  transition:
    background 0.15s ease,
    color 0.15s ease,
    border-color 0.15s ease;
}

.top-nav button:hover {
  background: #2a2a2a;
}

.top-nav button:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.top-nav button.is-active {
  background: #ffffff;
  color: var(--cosmic-black);
  border-color: var(--cosmic-black);
}

.layout-main {
  display: grid;
  grid-template-columns: minmax(200px, 230px) minmax(0, 1fr) minmax(180px, 220px);
  grid-template-rows: minmax(0, 1fr);
  gap: 16px;
  padding: 0;
  min-height: 0;
  height: 100%;
}

.layout-main > * {
  animation: panelReveal 0.6s ease-out both;
}

.layout-main > *:nth-child(1) {
  animation-delay: 0.05s;
}

.layout-main > *:nth-child(2) {
  animation-delay: 0.12s;
}

.layout-main > *:nth-child(3) {
  animation-delay: 0.18s;
}

.left-nav {
  /* ISS-DESIGN-001: left nav must remain flat (no border/background) */
  /* to give visual dominance to the calculator area */
  background: transparent;
  border: none;
  border-radius: 0;
  box-shadow: none;
  padding: 14px;
  overflow-y: scroll;
  scrollbar-gutter: stable;
  height: 100%;
  margin-left: -4px;
}

.left-nav-title {
  margin: 0 0 14px;
  font-size: 15px;
  font-weight: 600;
}

#left-nav-content {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.nav-search {
  position: sticky;
  top: 0;
  z-index: 1;
  background: var(--panel-bg);
  padding-bottom: 8px;
}

.nav-search-input {
  width: 100%;
  padding: var(--calculator-input-padding);
  border-radius: var(--calculator-input-radius);
  border: 1px solid var(--border-color);
  font-size: 14px;
  font-family: inherit;
  background: var(--panel-bg);
}

.nav-category {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.nav-category-toggle {
  width: 100%;
  border: none;
  background: transparent;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 6px 4px;
  color: var(--muted-text);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.6px;
  cursor: pointer;
}

.nav-category-toggle:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
  border-radius: 8px;
}

.nav-category-label {
  flex: 1;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.nav-category-indicator {
  font-weight: 600;
  color: var(--header-text);
  flex-shrink: 0;
}

.nav-category-items {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.nav-category.is-collapsed .nav-category-items {
  display: none;
}

#left-nav-content.is-searching .nav-category.is-search-open .nav-category-items {
  display: flex;
}

.left-nav .subcategory-title {
  margin: 16px 0 8px;
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.6px;
  color: var(--muted-text);
}

.left-nav .nav-item {
  width: 100%;
  text-align: left;
  background: var(--pill-bg);
  border-radius: 12px;
  padding: 10px 12px;
  font-size: 13px;
  color: var(--header-text);
  margin-bottom: 0;
  border: 1px solid var(--pill-border);
  cursor: pointer;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  transition:
    background 0.15s ease,
    box-shadow 0.15s ease;
}

.left-nav .nav-item.is-active {
  background: var(--accent);
  color: #ffffff;
  border-color: var(--accent-strong);
  box-shadow: 0 8px 14px rgba(37, 99, 235, 0.24);
}

.center-column {
  display: grid;
  /* REQ-20260119-004: Pane width distribution - Calculation 37.5%, Explanation 62.5% (3:5 ratio) */
  grid-template-columns: minmax(0, 3fr) minmax(0, 5fr);
  grid-template-rows: minmax(0, 1fr);
  gap: 16px;
  min-height: 0;
  height: 100%;
}

.panel {
  background: var(--panel-bg);
  border: 2px solid var(--shell-border);
  border-radius: 32px;
  box-shadow: var(--panel-shadow);
  padding: 24px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  min-height: 0;
  height: 100%;
}

.panel-scroll {
  overflow-y: scroll;
  scrollbar-gutter: stable;
  flex: 1;
  min-height: 0;
}

.panel h3 {
  margin: 0;
  font-size: 16px;
  font-weight: 600;
}

.panel .placeholder {
  color: var(--muted-text);
  font-size: 14px;
}

.ads-column {
  display: grid;
  grid-template-rows: minmax(220px, 1fr);
  gap: 12px;
  min-height: 0;
  background: var(--panel-bg);
  border: 2px solid var(--shell-border);
  border-radius: 28px;
  padding: 12px;
  height: 100%;
}

.ad-panel {
  background: #f8fafc;
  border: 2px dashed #e5e7eb;
  border-radius: 22px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--muted-text);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 1px;
}

.site-footer {
  border: none;
  background: transparent;
  border-radius: 0;
  padding: 6px 4px 4px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 20px;
  color: var(--muted-text);
  font-size: 15px;
  flex-wrap: wrap;
}

.site-footer a {
  color: var(--muted-text);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}

@keyframes shellLift {
  from {
    opacity: 0;
    transform: translateY(14px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes headerSlide {
  from {
    opacity: 0;
    transform: translateY(-8px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes panelReveal {
  from {
    opacity: 0;
    transform: translateY(10px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@media (prefers-reduced-motion: reduce) {
  .page,
  .site-header,
  .top-nav,
  .layout-main > * {
    animation: none;
  }
}

@media (max-width: 1200px) {
  .center-column {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 1024px) {
  .layout-main {
    grid-template-columns: 200px minmax(0, 1fr);
    padding: 0;
  }

  .ads-column {
    grid-column: 1 / -1;
    grid-template-columns: minmax(200px, 1fr);
    grid-template-rows: minmax(220px, 1fr);
  }
}

@media (max-width: 860px) {
  .page {
    margin: 12px;
    padding: 16px;
  }

  .layout-main {
    grid-template-columns: 1fr;
  }

  .left-nav {
    margin-left: 0;
  }

  .ads-column {
    grid-template-columns: 1fr;
    grid-template-rows: minmax(180px, 1fr);
  }
}