* {
  box-sizing: border-box;
}

html, body {
  height: 100%;
  margin: 0;
}

body {
  font-family: var(--font-base);
  font-size: var(--font-size-base);
  color: var(--color-text);
  background: var(--color-bg);
  display: flex;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
}

#app {
  display: flex;
  flex-direction: column;
  height: 100vh;
}

header.app-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: var(--tab-height);
  padding: 0 var(--space-lg);
  border-bottom: 1px solid var(--color-border-faint);
  background: var(--color-surface);
  flex-shrink: 0;
  gap: var(--space-lg);
}

.brand {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

header.app-header h1 {
  font-family: var(--font-display);
  font-size: 21px;
  font-weight: 500;
  margin: 0;
  letter-spacing: 0.01em;
}

/*
 * The tab count grows as reference sections are added, so this scrolls
 * sideways rather than wrapping to a second row or shoving the search and
 * theme controls off the end: min-width 0 lets it shrink below its content
 * width inside the header flex row, and the scrollbar is hidden since the
 * tabs are the only affordance that matters here.
 */
nav.tabs {
  display: flex;
  gap: var(--space-md);
  margin-right: auto;
  padding-left: var(--space-xl);
  min-width: 0;
  overflow-x: auto;
  scrollbar-width: none;
  -ms-overflow-style: none;
}

nav.tabs::-webkit-scrollbar {
  display: none;
}

/*
 * Marks the seam between the five history/genealogy views (Tree through
 * Journey) and the ten subject-reference tabs (Quran through End Times),
 * so the row reads as two related groups instead of one flat list a
 * person has to scroll sideways through blind.
 */
.tabs-divider {
  flex: 0 0 auto;
  align-self: stretch;
  width: 1px;
  margin: var(--space-sm) 2px;
  background: var(--color-border-faint);
}

nav.tabs button {
  flex: 0 0 auto;
  white-space: nowrap;
  font-family: inherit;
  font-size: 14px;
  font-weight: 500;
  padding: 4px 2px;
  background: transparent;
  color: var(--color-text-faint);
  border: none;
  border-bottom: 2px solid transparent;
  cursor: pointer;
  transition: color 0.18s var(--ease-standard), border-color 0.18s var(--ease-standard);
}

nav.tabs button:hover {
  color: var(--color-text);
}

nav.tabs button.active {
  color: var(--color-text);
  border-bottom-color: var(--color-text);
}

.theme-toggle {
  display: flex;
  align-items: center;
  gap: 7px;
  font-family: inherit;
  font-size: 13px;
  padding: 6px 12px;
  background: transparent;
  color: var(--color-text-muted);
  border: 1px solid var(--color-border-soft);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: color 0.15s ease, border-color 0.15s ease;
}

.theme-toggle:hover {
  color: var(--color-text);
  border-color: var(--color-text);
}

.icon {
  display: block;
  flex-shrink: 0;
}

main.view-container {
  position: relative;
  flex: 1;
  overflow: hidden;
}

.view {
  position: absolute;
  inset: 0;
  overflow: hidden;
  display: none;
}

.view.active {
  display: block;
}

.view-scroll {
  height: 100%;
  overflow: auto;
}

@media (max-width: 640px) {
  header.app-header {
    padding: 0 var(--space-md);
    gap: var(--space-md);
  }

  nav.tabs {
    padding-left: 0;
    gap: var(--space-md);
  }

  .theme-toggle {
    padding: 6px 8px;
    font-size: 12px;
  }

  /* Reclaims header width for the scrolling tabs and the search input,
     the two things worth the room on a narrow screen; the sun/moon icon
     alone still says what the button does. */
  #theme-toggle-label {
    display: none;
  }
}