/*
 * App shell and the three-column builder (SPEC 12, 64).
 *
 * One DOM tree serves every breakpoint: the preview becomes a tab below
 * 1024px and the step trail turns into a horizontal strip below 768px.
 */

/*
 * App-shell layout: the shell owns the viewport and the inner panels scroll.
 * If the document itself scrolled, the sticky header would slide over the
 * mobile tab strip as soon as anything moved the viewport.
 * dvh keeps this honest while mobile browser chrome expands and collapses.
 */
#app {
  display: flex;
  flex-direction: column;
  height: 100vh;
  height: 100dvh;
  overflow: hidden;
}

/* ------------------------------- header -------------------------------- */

.header {
  position: sticky;
  top: 0;
  z-index: var(--z-header);
  display: flex;
  align-items: center;
  gap: var(--space-5);
  height: var(--header-height);
  padding: 0 var(--space-5);
  background: color-mix(in srgb, var(--surface) 88%, transparent);
  backdrop-filter: saturate(180%) blur(12px);
  border-bottom: 1px solid var(--border-subtle);
  flex: none;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  color: var(--text-primary);
  text-decoration: none;
  flex: none;
}

.brand:hover {
  text-decoration: none;
}

.brand__name {
  font-size: 15px;
  font-weight: var(--weight-bold);
  letter-spacing: -0.02em;
}

.breadcrumb {
  display: flex;
  align-items: center;
  gap: var(--space-1);
  min-width: 0;
  font-size: var(--text-label);
  color: var(--text-secondary);
  overflow: hidden;
}

.breadcrumb__sep {
  display: inline-flex;
  color: var(--text-disabled);
}

.breadcrumb__link {
  color: var(--text-secondary);
  white-space: nowrap;
}

.breadcrumb__current {
  color: var(--text-primary);
  font-weight: var(--weight-label);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.header__actions {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  margin-left: auto;
  flex: none;
}

.header__search {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  width: 260px;
  padding: 7px 10px;
  color: var(--text-muted);
  background: var(--surface-muted);
  border: 1px solid transparent;
  border-radius: var(--radius-md);
  font-size: var(--text-label);
  transition: border-color var(--duration-fast) var(--ease-out);
}

.header__search:hover {
  border-color: var(--border-default);
}

.header__search-label {
  flex: 1;
  text-align: left;
}

.header__kbd,
.palette__kbd {
  padding: 1px 5px;
  font-family: var(--font-sans);
  font-size: 11px;
  color: var(--text-muted);
  background: var(--surface);
  border: 1px solid var(--border-default);
  border-radius: 4px;
}

/* -------------------------------- pages -------------------------------- */

.page {
  flex: 1;
  min-height: 0;
  overflow-y: auto;
  padding: var(--space-10) var(--space-6) var(--space-16);
}

.page > * {
  width: 100%;
  max-width: 1120px;
  margin: 0 auto;
}

.page:focus {
  outline: none;
}

/* ------------------------------- builder ------------------------------- */

.builder-view {
  display: flex;
  flex-direction: column;
  flex: 1;
  min-height: 0;
}

/*
 * Both side panels collapse independently. The column widths are custom
 * properties so the grid can be driven by two data attributes instead of four
 * hand-written combinations, and so the width change is a single smooth
 * transition rather than a jump.
 */
.builder {
  --col-sidebar: var(--sidebar-width);
  --col-preview: var(--preview-width);

  display: grid;
  grid-template-columns: var(--col-sidebar) minmax(0, 1fr) var(--col-preview);
  flex: 1;
  min-height: 0;
  transition: grid-template-columns var(--duration-panel) var(--ease-out);
}

.builder[data-sidebar='collapsed'] {
  --col-sidebar: var(--sidebar-rail);
}

.builder[data-preview='collapsed'] {
  --col-preview: var(--preview-rail);
}

.sidebar {
  border-right: 1px solid var(--border-subtle);
  padding: var(--space-6) var(--space-4);
  overflow-y: auto;
  /* The rail is narrower than the labels it hides; clipping horizontally keeps
     a scrollbar from appearing while the panel animates shut. */
  overflow-x: hidden;
  transition: padding var(--duration-panel) var(--ease-out);
}

.builder[data-sidebar='collapsed'] .sidebar {
  padding-inline: var(--space-2);
}

.builder__content {
  min-width: 0;
  overflow-y: auto;
  padding: var(--space-8) var(--space-8) var(--space-16);
}

.builder__content:focus {
  outline: none;
}

.preview {
  display: flex;
  flex-direction: column;
  min-width: 0;
  border-left: 1px solid var(--border-subtle);
  background: var(--surface-secondary);
  overflow: hidden;
}

.mobile-tabs {
  display: none;
}

/* ---------------------------- 1024 and below --------------------------- */

@media (max-width: 1023px) {
  .builder {
    grid-template-columns: 200px minmax(0, 1fr);
  }

  .mobile-tabs {
    display: flex;
    gap: var(--space-1);
    padding: var(--space-2) var(--space-4);
    border-bottom: 1px solid var(--border-subtle);
    background: var(--surface);
  }

  .mobile-tab {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 7px 14px;
    border-radius: var(--radius-pill);
    font-size: var(--text-label);
    font-weight: var(--weight-label);
    color: var(--text-secondary);
  }

  .mobile-tab[aria-selected='true'] {
    color: var(--text-primary);
    background: var(--surface-muted);
  }

  .builder[data-tab='builder'] .preview {
    display: none;
  }

  .builder[data-tab='preview'] .sidebar,
  .builder[data-tab='preview'] .builder__content {
    display: none;
  }

  .builder[data-tab='preview'] {
    grid-template-columns: minmax(0, 1fr);
  }

  .builder[data-tab='preview'] .preview {
    border-left: none;
  }

  .header__search {
    width: 44px;
  }

  .header__search-label,
  .header__kbd {
    display: none;
  }
}

/* ----------------------------- 768 and below --------------------------- */

@media (max-width: 767px) {
  .header {
    gap: var(--space-3);
    padding: 0 var(--space-4);
  }

  .breadcrumb {
    display: none;
  }

  .builder {
    grid-template-columns: minmax(0, 1fr);
    grid-template-rows: auto minmax(0, 1fr);
  }

  /* The step trail becomes a horizontally scrolling strip (SPEC 64). */
  .builder[data-tab='builder'] .sidebar {
    display: block;
    border-right: none;
    border-bottom: 1px solid var(--border-subtle);
    padding: var(--space-3) var(--space-4);
    overflow-x: auto;
    overflow-y: hidden;
  }

  .builder__content {
    padding: var(--space-6) var(--space-4) var(--space-12);
  }

  .page {
    padding: var(--space-6) var(--space-4) var(--space-12);
  }
}