*,
*::before,
*::after {
  box-sizing: border-box;
}

html,
body {
  height: 100%;
  margin: 0;
  overflow-x: clip;
  max-width: 100%;
}

body {
  font-family: var(--font-ui);
  font-size: var(--text-base);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
  --keyboard-zindex: 400;
}

.app {
  display: grid;
  grid-template-rows: auto 1fr;
  width: 100%;
  min-width: 0;
  height: 100dvh;
  overflow-x: clip;
  background: var(--color-bg);
  color: var(--color-text);
}

/* ── Top bar ── */
.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  padding: var(--space-3) var(--space-5);
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  box-shadow: var(--shadow-sm);
  z-index: 10;
}

.topbar__brand {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  min-width: 0;
}

.topbar__title {
  margin: 0;
  font-size: var(--text-lg);
  font-weight: 600;
  color: var(--color-text);
  white-space: nowrap;
}

.topbar__subtitle {
  margin: 0;
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  display: none;
}

.topbar__actions {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  flex-shrink: 0;
}

/* ── Workspace grid ── */
.workspace {
  display: grid;
  grid-template-columns: var(--col-left) minmax(0, 1fr) var(--col-right);
  min-height: 0;
  overflow: hidden;
  max-width: 1800px;
  margin-inline: auto;
  width: 100%;
}

.workspace > * {
  min-height: 0;
  min-width: 0;
  overflow-y: auto;
}

.workspace--palette-collapsed {
  grid-template-columns: minmax(0, 1fr) var(--col-right);
}

.workspace--palette-collapsed .panel-region--palette {
  display: none;
}

.workspace--set-collapsed {
  grid-template-columns: var(--col-left) minmax(0, 1fr);
}

.workspace--set-collapsed .panel-region--set {
  display: none;
}

.workspace--palette-collapsed.workspace--set-collapsed {
  grid-template-columns: minmax(0, 1fr);
}

/* ── Panel regions ── */
.panel-region {
  background: var(--color-surface);
  border-right: 1px solid var(--color-border);
  display: flex;
  flex-direction: column;
}

.panel-region--set {
  border-right: none;
  border-left: 1px solid var(--color-border);
}

.panel-region__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-3) var(--space-4);
  border-bottom: 1px solid var(--color-border);
  flex-shrink: 0;
  background: var(--color-surface);
  position: sticky;
  top: 0;
  z-index: 2;
}

.panel-region__title {
  margin: 0;
  font-size: var(--text-sm);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--color-text-muted);
}

.panel-region__body {
  flex: 1;
  padding: var(--space-4);
  min-height: 0;
}

.palette-mount {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

/* ── Editor column ── */
.editor-column {
  display: flex;
  flex-direction: column;
  min-height: 0;
  background: var(--color-bg);
  overflow: hidden;
}

.editor-canvas {
  flex: 1;
  overflow-y: auto;
  padding: var(--space-5);
  min-height: 0;
}

.editor-canvas__inner {
  width: 100%;
  min-width: 0;
  max-width: 900px;
  margin-inline: auto;
}

.editor-canvas__tools {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin-top: var(--space-4);
}

.editor-empty-hint {
  margin: var(--space-3) 0 0;
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  text-align: center;
}

.editor-empty-hint kbd {
  padding: 2px 6px;
  border-radius: var(--radius-sm);
  background: var(--color-surface-2);
  border: 1px solid var(--color-border);
  font-family: var(--font-mono);
  font-size: 0.8125rem;
}

.editor-export-bar {
  flex-shrink: 0;
  min-width: 0;
  position: sticky;
  bottom: 0;
  background: var(--color-surface);
  border-top: 1px solid var(--color-border);
  padding: var(--space-4) var(--space-5);
  box-shadow: 0 -4px 12px rgba(15, 32, 48, 0.06);
  z-index: 5;
}

/* ── Palette reopen tab (when collapsed) ── */
.btn.palette-rail {
  display: none;
  position: fixed;
  left: 0;
  top: 3.25rem;
  z-index: 20;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  box-shadow: var(--shadow-sm);
}

.app--palette-collapsed .btn.palette-rail {
  display: inline-flex;
}

/* ── Equation set reopen tab (when collapsed) ── */
.btn.set-rail {
  position: fixed;
  right: 0;
  top: 3.25rem;
  z-index: 100;
  border-radius: var(--radius-sm) 0 0 var(--radius-sm);
  box-shadow: var(--shadow-sm);
}

.btn.set-rail[hidden] {
  display: none !important;
}

/* ── Palette drawer (tablet) ── */
.palette-drawer-backdrop {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(15, 32, 48, 0.4);
  z-index: 30;
}

.palette-drawer-backdrop.is-open {
  display: block;
}

.palette-drawer {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  bottom: 0;
  width: min(320px, 90vw);
  z-index: 31;
  background: var(--color-surface);
  box-shadow: var(--shadow-lg);
  transform: translateX(-100%);
  transition: transform 0.25s ease;
  flex-direction: column;
}

.palette-drawer.is-open {
  display: flex;
  transform: translateX(0);
}

/* ── Mobile tab bar ── */
.mobile-tabs {
  display: none;
  grid-template-columns: 1fr 1fr 1fr;
  border-top: 1px solid var(--color-border);
  background: var(--color-surface);
  flex-shrink: 0;
}

.mobile-tab {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: var(--space-1);
  min-height: 56px;
  padding: var(--space-2);
  border: none;
  background: transparent;
  color: var(--color-text-muted);
  font-family: var(--font-ui);
  font-size: var(--text-sm);
  font-weight: 600;
  cursor: pointer;
}

.mobile-tab.is-active {
  color: var(--color-accent);
  background: var(--color-accent-soft);
}

.mobile-tab:focus-visible {
  outline: none;
  box-shadow: var(--ring);
}

/* ── Skip link ── */
.skip-link {
  position: absolute;
  left: var(--space-4);
  top: -100px;
  z-index: 300;
  padding: var(--space-2) var(--space-4);
  background: var(--color-primary);
  color: #fff;
  border-radius: var(--radius-sm);
  font-weight: 600;
  text-decoration: none;
}

.skip-link:focus {
  top: var(--space-4);
  outline: none;
  box-shadow: var(--ring);
}

/* ── Responsive ── */
@media (min-width: 1100px) {
  .topbar__subtitle {
    display: block;
  }
}

@media (max-width: 1099px) {
  .workspace {
    grid-template-columns: minmax(0, 1fr) 320px;
  }

  .panel-region--palette,
  .app--palette-collapsed .btn.palette-rail {
    display: none;
  }

  .panel-region--set {
    display: flex;
  }
}

@media (max-width: 767px) {
  .app {
    grid-template-rows: auto 1fr auto;
  }

  .workspace {
    grid-template-columns: 1fr;
    grid-template-rows: 1fr;
  }

  .panel-region--set {
    display: none;
    border-left: none;
  }

  .panel-region--palette {
    display: none;
  }

  .mobile-tabs {
    display: grid;
    z-index: 50;
    padding-bottom: env(safe-area-inset-bottom, 0);
  }

  body.keyboard-visible .mobile-tabs {
    display: none;
  }

  .editor-canvas {
    padding: var(--space-3);
  }

  .editor-export-bar {
    padding: var(--space-3);
  }

  .topbar {
    padding: var(--space-2) var(--space-3);
  }

  .topbar__brand {
    flex: 1;
  }

  .topbar__title {
    font-size: var(--text-base);
    overflow: hidden;
    text-overflow: ellipsis;
  }

  .topbar__actions .btn--icon {
    min-width: 40px;
    min-height: 40px;
  }

  #btn-toggle-palette,
  #btn-topbar-set {
    display: none;
  }

  .app.mobile-tab-palette .editor-column,
  .app.mobile-tab-set .editor-column {
    display: none;
  }

  .app.mobile-tab-palette .panel-region--palette,
  .app.mobile-tab-set .panel-region--set {
    display: flex;
    border: none;
    grid-column: 1;
    grid-row: 1;
  }

  .topbar__subtitle {
    display: none;
  }

  .export-bar__actions {
    flex-direction: column;
  }

  .export-bar__actions .btn,
  .export-bar__latex-group {
    width: 100%;
  }

  .export-bar__latex-group {
    display: flex;
  }

  .export-bar__latex-group .btn {
    flex: 1;
  }

  .export-bar__target-select {
    flex: 1;
    max-width: none;
    border-left: 1px solid var(--color-border);
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  }

  .export-bar__controls {
    flex-direction: column;
    align-items: stretch;
    gap: var(--space-3);
  }

  .export-bar__control {
    flex-direction: column;
    align-items: stretch;
    width: 100%;
  }

  .export-bar__control select {
    width: 100%;
  }
}

/* ── Load error ── */
.load-error {
  display: none;
  padding: var(--space-5);
  margin: var(--space-5);
  background: var(--color-surface);
  border: 1px solid var(--color-danger);
  border-radius: var(--radius-md);
  color: var(--color-danger);
}

.load-error.is-visible {
  display: block;
}