/* Top lessons: the lesson card grid (index and home) and the lesson page. Lessons are exported
   images read from a manifest, not authored markup. */

/* ---- Lesson cards ---- */
/* Images inside controls and pages, declared first so later state rules win. */
.viewer-step > span {
  display: inline-flex;
}
.viewer-thumb img {
  display: block;
  width: 100%;
}
.paper-page img {
  display: block;
  width: 100%;
  border: 1px solid rgb(41 59 50 / 0.12);
  border-radius: var(--radius-paper);
  background: white;
  box-shadow: 0 20px 40px -26px rgb(41 59 50 / 0.45);
}
.lesson-grid {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: clamp(2rem, 3vw, 2.5rem) clamp(1.25rem, 2vw, 1.75rem);
}
.lesson-card > a {
  display: flex;
  flex-direction: column;
  height: 100%;
  text-decoration: none;
  border-radius: var(--radius-card);
}
.lesson-card-cover {
  display: block;
  aspect-ratio: 16 / 9;
  border: 1px solid rgb(41 59 50 / 0.14);
  border-radius: var(--radius-card);
  overflow: hidden;
  background: var(--paper);
  transition:
    transform 0.3s var(--ease),
    box-shadow 0.3s var(--ease);
}
.lesson-card-cover img {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: cover;
}
.lesson-card-meta {
  margin-top: 1.1rem;
  font-size: var(--text-sm);
  font-weight: 500;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--muted);
}
.lesson-card-title {
  margin-top: 0.4rem;
  font-size: 1.375rem;
  line-height: 1.2;
  letter-spacing: -0.02em;
  text-decoration: underline;
  text-decoration-color: transparent;
  text-decoration-thickness: 1px;
  text-underline-offset: 5px;
  transition: text-decoration-color 0.2s;
}
.lesson-card-materials {
  margin-top: 0.5rem;
  font-size: 1rem;
  color: var(--muted);
}
.lesson-card > a:hover .lesson-card-cover,
.lesson-card > a:focus-visible .lesson-card-cover {
  transform: translateY(-4px);
  box-shadow: 0 14px 30px -14px rgb(41 59 50 / 0.45);
}
.lesson-card > a:hover .lesson-card-title,
.lesson-card > a:focus-visible .lesson-card-title {
  text-decoration-color: currentColor;
}

/* ---- Lesson page ---- */
/* The head is two lines: where you are, and the lesson's title. Everything else is on the page. */
.lesson-head {
  padding-block: clamp(0.5rem, 1.5vw, 1rem) clamp(1.25rem, 2.5vw, 1.75rem);
}
.lesson-crumbs {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.2rem 0.6rem;
  margin-bottom: 0.5rem;
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--muted);
}
.lesson-crumbs a {
  display: inline-flex;
  align-items: center;
  min-height: 44px;
  color: var(--ink);
  text-decoration: underline;
  text-underline-offset: 4px;
  text-decoration-thickness: 1px;
}
.lesson-crumbs a:hover {
  text-decoration-thickness: 2px;
}
.lesson-head h1 {
  font-size: clamp(2rem, 3.2vw, 2.875rem);
  max-width: 28ch;
}
.lesson-block {
  padding-bottom: clamp(2.5rem, 5vw, 4rem);
}

/* Questions | Answers: one quiet segmented control, the same on slides and on paper. The chosen
   side is a raised paper chip on a soft track, so three of them on a page stay calm. */
.view-switch {
  display: inline-flex;
  padding: 3px;
  border-radius: 99px;
  background: rgb(41 59 50 / 0.07);
}
.view-switch button {
  min-height: 36px;
  padding: 0 0.9rem;
  border: 0;
  border-radius: 99px;
  background: transparent;
  color: var(--muted);
  font-size: 0.9375rem;
  font-weight: 500;
  transition:
    background 0.2s,
    color 0.2s,
    box-shadow 0.2s;
}
.view-switch button[aria-pressed="true"] {
  background: var(--paper);
  color: var(--ink);
  font-weight: 600;
  box-shadow:
    0 1px 2px rgb(41 59 50 / 0.18),
    0 0 0 1px rgb(41 59 50 / 0.06);
}
.view-switch button:focus-visible {
  outline-offset: 2px;
}
/* On a slide without answers the control keeps its place, so nothing jumps between slides. */
.view-switch[data-idle] {
  visibility: hidden;
}

/* Slides. Without JavaScript every slide is visible in a grid. */
.viewer-slides {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: clamp(1rem, 2vw, 1.5rem);
}
.viewer-slide img {
  display: block;
  width: 100%;
  border: 1px solid rgb(41 59 50 / 0.14);
  border-radius: var(--radius-card);
  background: var(--paper);
}
/* With JavaScript: one stage slide and a thumbnail strip. */
.viewer[data-enhanced] .viewer-slides {
  display: block;
}
.viewer[data-enhanced] .viewer-slide:not(.is-current) {
  display: none;
}
.viewer[data-enhanced] .viewer-slide img {
  box-shadow: 0 24px 50px -30px rgb(41 59 50 / 0.5);
}
/* Every control in one row right under the slide: where you are, the answers, previous, next. */
.viewer-controls {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: center;
  gap: 1rem 1.25rem;
  margin-top: 1rem;
}
.viewer-actions {
  display: flex;
  align-items: center;
  gap: 0.6rem;
}
.viewer-actions .view-switch {
  margin-right: 0.4rem;
}
.viewer-thumbs {
  grid-column: 1 / -1;
}
.viewer-status {
  white-space: nowrap;
  font-size: 1rem;
  font-weight: 500;
  color: var(--muted);
  font-variant-numeric: tabular-nums;
}
.viewer-step {
  display: inline-grid;
  place-items: center;
  width: 48px;
  height: 48px;
  border: 1px solid var(--control-border);
  border-radius: 50%;
  background: var(--paper);
  font-size: 1.3rem;
  transition:
    background 0.2s,
    color 0.2s;
}
.viewer-flip {
  transform: scaleX(-1);
}
/* The strip pads for the focus ring and pulls back so thumbnails sit on the grid edge. */
.viewer-thumbs {
  position: relative;
  display: grid;
  grid-auto-flow: column;
  /* Every slide on one strip, however long the lesson; a phone scrolls it instead. */
  grid-auto-columns: calc(
    (100% - (max(var(--count, 6), 6) - 1) * 0.75rem) /
    max(var(--count, 6), 6)
  );
  gap: 0.75rem;
  overflow-x: auto;
  margin: -9px;
  padding: 9px;
  scrollbar-width: thin;
}
.viewer-thumb {
  display: block;
  padding: 0;
  border: 1px solid rgb(41 59 50 / 0.14);
  border-radius: var(--radius);
  background: var(--paper);
  overflow: hidden;
  opacity: 0.62;
  transition:
    opacity 0.2s,
    box-shadow 0.2s;
}
.viewer-thumb[aria-current="true"] {
  opacity: 1;
  box-shadow:
    0 0 0 2px var(--cream),
    0 0 0 4px var(--ink);
}

/* Worksheet and exit ticket: paper pages side by side, each with its own answers switch. */
.lesson-papers {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: clamp(1.5rem, 4vw, 3rem);
  align-items: start;
}
.paper-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  min-height: 44px;
  margin-bottom: 0.75rem;
}
.paper-title {
  font-size: 1.25rem;
  font-weight: 600;
  letter-spacing: -0.01em;
}
.paper-page {
  margin: 0;
}
.paper-page + .paper-page {
  margin-top: 1.5rem;
}
/* Without JavaScript the answers follow the sheet; with it they replace it in the same place. */
.paper-answers {
  margin-top: 1.5rem;
}
.paper-answers-label {
  font-weight: 600;
  margin-bottom: 0.75rem;
}
.paper-doc[data-enhanced] .paper-answers {
  margin-top: 0;
}
.paper-doc[data-enhanced] .paper-answers-label {
  display: none;
}

@media (max-width: 1100px) {
  .lesson-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}
/* Hover styles only where there is a real pointer; on touch a tap would leave them stuck on. */
@media (hover: hover) {
  .viewer-step:hover {
    background: var(--ink);
    color: var(--cream);
  }
  .view-switch button:hover {
    color: var(--ink);
  }
  .viewer-thumb:hover {
    opacity: 1;
  }
}
/* Phone: the slide and the sheets run edge to edge, and the controls shrink to one quiet row:
   previous, where you are, next, and the answers switch. Thumbnails give way to swiping. */
@media (max-width: 760px) {
  .lesson-head {
    padding-block: 0 1rem;
  }
  .lesson-crumbs {
    margin-bottom: 0.1rem;
    font-size: 0.875rem;
  }
  .lesson-head h1 {
    font-size: 1.75rem;
  }
  .viewer-slides,
  .paper-sheet,
  .paper-answers {
    margin-inline: calc(-1 * var(--gutter));
  }
  .viewer-slides {
    grid-template-columns: 1fr;
    gap: 0.75rem;
  }
  .paper-doc .paper-page img,
  .viewer .viewer-slide img {
    border-inline: 0;
    border-radius: 0;
    box-shadow: none;
  }
  .viewer[data-enhanced] .viewer-slide img {
    box-shadow: none;
  }
  .viewer-controls {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-top: 0.75rem;
  }
  .viewer-actions {
    display: contents;
  }
  .viewer-step {
    width: 44px;
    height: 44px;
    border: 0;
    border-radius: 50%;
    background: transparent;
    font-size: 1.25rem;
  }
  .viewer-step[data-step="-1"] {
    order: 1;
  }
  .viewer-status {
    order: 2;
    min-width: 3.6em;
    text-align: center;
    font-size: 0.9375rem;
    font-variant-numeric: tabular-nums;
  }
  /* "Slide 3 of 10" is still read out; the eye gets "3 / 10". */
  .vs-word {
    position: absolute;
    width: 1px;
    height: 1px;
    overflow: hidden;
    clip-path: inset(50%);
    white-space: nowrap;
  }
  .vs-total::before {
    content: "/";
    margin-inline: 0.3em 0.05em;
  }
  .viewer-step[data-step="1"] {
    order: 3;
  }
  .viewer-actions .view-switch {
    order: 4;
    margin: 0 0 0 auto;
  }
  .view-switch button {
    min-height: 34px;
    padding: 0 0.7rem;
    font-size: 0.875rem;
  }
  .viewer-controls {
    gap: 0.25rem;
  }
  .viewer-thumbs {
    display: none;
  }
  .lesson-block {
    padding-bottom: 1.75rem;
  }
  .lesson-papers {
    grid-template-columns: 1fr;
    gap: 2.5rem;
  }
  /* The sheets start below a rule, so their controls never read as the slide's. */
  .lesson-block + .lesson-block > .lesson-papers {
    border-top: 1px solid var(--line);
    padding-top: 1.75rem;
  }
  .viewer-step:active {
    opacity: 0.55;
  }
  /* The narrow layout's arrows are bare icons: a soft round wash on hover, never a filled block. */
  .viewer-step:hover {
    background: rgb(41 59 50 / 0.07);
    color: var(--ink);
  }
  .paper-bar {
    margin-bottom: 0.6rem;
  }
  .paper-title {
    font-size: 1.125rem;
  }
}
@media (max-width: 560px) {
  .lesson-grid {
    grid-template-columns: 1fr;
  }
}