/*
 * The application shell and the stack of layers.
 *
 * Three layers are stacked in the same place. Layer i is shifted slightly to
 * the right and down, so the title strip of the layer underneath keeps peeking
 * out and can be clicked to go back. A layer that has not been opened yet
 * waits below the screen.
 */

.app {
  display: grid;
  grid-template-rows: var(--topbar-h) minmax(0, 1fr);
  height: 100vh;
  height: 100dvh;
  overflow: hidden;
}

/* ---------------------------------------------------------------------------
 * Top bar
 * ------------------------------------------------------------------------- */

.topbar {
  --focus: var(--yellow);
  position: relative;
  z-index: var(--z-topbar);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  padding: 0 var(--gutter);
  background: var(--ink);
  color: var(--paper);
}

.brand {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  min-height: 44px;
  text-decoration: none;
}

.brand__mark {
  position: relative;
  width: 30px;
  height: 30px;
}

.brand__mark i {
  position: absolute;
  width: 18px;
  height: 18px;
  border: 2px solid var(--ink);
}

.brand__mark i:nth-child(1) {
  top: 0;
  left: 0;
  background: var(--yellow);
}

.brand__mark i:nth-child(2) {
  top: 6px;
  left: 6px;
  background: var(--paper);
}

.brand__mark i:nth-child(3) {
  top: 12px;
  left: 12px;
  background: var(--pink);
}

.brand__name {
  font-family: var(--font-display);
  font-size: var(--text-xl);
  font-weight: 800;
  letter-spacing: -0.02em;
}

.steps {
  display: flex;
  gap: var(--space-1);
}

.steps__link {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  min-height: 44px;
  padding: 0 var(--space-3);
  border: var(--border-thin) solid transparent;
  font-weight: 700;
  text-decoration: none;
  transition:
    background-color var(--dur-fast),
    color var(--dur-fast);
}

.steps__link b {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  opacity: 0.7;
}

.steps__link:hover {
  border-color: var(--paper);
}

.steps__link[aria-current='step'] {
  background: var(--step-color, var(--yellow));
  color: var(--ink);
}

.steps__link[aria-current='step'] b {
  opacity: 1;
}

.steps__link[data-layer-link='results'] {
  --step-color: var(--paper);
}

.steps__link[data-layer-link='live'] {
  --step-color: var(--pink);
}

@media (max-width: 480px) {
  .brand__name {
    display: none;
  }

  .steps__link {
    padding: 0 var(--space-2);
  }
}

/* On the narrowest phones the step numbers give way to the labels. */
@media (max-width: 360px) {
  .steps__link b {
    display: none;
  }
}

/* ---------------------------------------------------------------------------
 * Layer stack
 * ------------------------------------------------------------------------- */

.stack {
  position: relative;
  margin: 0 clamp(8px, 1.6vw, 20px);
  overflow: clip;
}

.layer {
  position: absolute;
  inset: calc(var(--i) * var(--peek-y)) 0 0 calc(var(--i) * var(--peek-x));
  z-index: calc(var(--z-layer) + var(--i));
  display: flex;
  flex-direction: column;
  background: var(--surface);
  color: var(--on-surface);
  border: var(--border) solid var(--ink);
  border-bottom: 0;
  transition:
    transform var(--dur-layer-in) var(--ease-out),
    visibility 0s;
  will-change: transform;
}

.layer--live {
  border-color: var(--night-line);
}

/* A layer not opened yet: it sits below the screen. Leaving is faster than entering. */
.layer[data-state='ahead'] {
  transform: translateY(calc(100% + 16px));
  visibility: hidden;
  transition:
    transform var(--dur-layer-out) var(--ease-in),
    visibility 0s linear var(--dur-layer-out);
}

.layer__tab {
  position: relative;
  flex: none;
  display: flex;
  align-items: center;
  gap: var(--space-3);
  height: var(--peek-y);
  padding: 0 var(--space-4);
  border-bottom: var(--border) solid var(--line);
}

.layer__num {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  font-weight: 700;
  padding: 2px 8px;
  background: var(--accent);
  color: var(--on-accent);
}

.layer__title {
  font-family: var(--font-display);
  font-size: var(--text-lg);
  font-weight: 800;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.layer__title:focus-visible {
  outline-offset: 4px;
}

.layer__hint {
  color: var(--on-surface-muted);
  font-size: var(--text-sm);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

/* The title strip of a layer underneath turns into a link for going back. */
.layer__return {
  display: none;
  position: absolute;
  inset: 0;
  align-items: center;
  justify-content: flex-end;
  gap: var(--space-2);
  padding: 0 var(--space-4);
  font-size: var(--text-sm);
  font-weight: 700;
  text-decoration: none;
  cursor: pointer;
}

.layer__return span {
  text-decoration: underline;
  text-decoration-thickness: 2px;
  text-underline-offset: 3px;
}

.layer[data-state='behind'] .layer__return {
  display: flex;
}

.layer[data-state='behind'] .layer__return:hover {
  background: color-mix(in srgb, var(--on-surface) 12%, transparent);
}

.layer[data-state='behind'] .layer__return:focus-visible {
  outline-offset: -5px;
}

.layer[data-state='behind'] .layer__hint {
  display: none;
}

.layer__body {
  flex: 1;
  min-height: 0;
  overflow: hidden auto;
  overscroll-behavior: contain;
  /* A focused field must not be covered by the action bar stuck to the bottom. */
  scroll-padding-block: var(--space-5) 120px;
}

.wrap {
  max-width: 1240px;
  margin: 0 auto;
  padding: clamp(20px, 3.5vw, 48px) var(--gutter) var(--space-8);
}

@media (max-width: 720px) {
  .layer__hint {
    display: none;
  }
}

/* ---------------------------------------------------------------------------
 * Empty states (layers 02 and 03 before a simulation has run)
 * ------------------------------------------------------------------------- */

.empty {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: var(--space-4);
  max-width: 34rem;
  padding: var(--space-7) 0;
}

.empty__num {
  font-family: var(--font-mono);
  font-size: clamp(5rem, 18vw, 9rem);
  font-weight: 700;
  line-height: 0.8;
  -webkit-text-stroke: 3px var(--on-surface);
  color: transparent;
}

.empty__title {
  font-family: var(--font-display);
  font-size: var(--text-2xl);
  font-weight: 800;
  line-height: 1.1;
}

.actions {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  margin-top: var(--space-6);
}

.footnote {
  margin-top: var(--space-5);
  color: var(--on-surface-muted);
  font-size: var(--text-sm);
  max-width: 70ch;
}