/* PyPath — the unit overview page (units/unit-N.html, data/unit-N.html).
 *
 * A header that says what the unit is and how far through it you are, then the
 * lessons as a trail: one rail, a stop per lesson, the unit test as the summit.
 * Markup from scripts/build-unit-pages.mjs; states from unit-progress-panel.js
 * (is-done, is-started, is-up-next) and lesson-progress.js (the test line).
 *
 * Colours are the site's --pp-* tokens, which pypath-theme.css switches for the
 * dark theme and for Python for Data, so one sheet serves all four. No
 * gradients (tests/course-theme.test.js); breakpoints on the scale
 * (docs/css-breakpoints.md). */

.unit-layout {
  --rail: 23px;          /* centre of the rail, from the list's left edge */
  --dot: 40px;
  /* Same gutters as the lesson pages: the page uses its width, on purpose. */
  --gutter: clamp(1.25rem, 4vw, 4.25rem);
  display: grid;
  grid-template-columns: minmax(300px, 380px) minmax(0, 1fr);
  column-gap: clamp(2rem, 4vw, 4rem);
  align-items: start;
  box-sizing: border-box;
  width: 100%;
  padding: clamp(1.25rem, 3vw, 2.5rem) var(--gutter) clamp(2.5rem, 6vw, 4.5rem);
}

/* ── header ───────────────────────────────────────────────── */
.unit-hero {
  /* The header stays beside the lessons while you read down the trail. */
  position: sticky;
  top: calc(var(--header-height, 72px) + 1.25rem);
  min-width: 0;
}

.unit-hero .breadcrumb a {
  color: var(--pp-line-ink);
  font-weight: 600;
  text-decoration: none;
}
.unit-hero .breadcrumb a:hover { text-decoration: underline; }

.unit-hero__eyebrow {
  margin: 1rem 0 0.35rem;
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--pp-muted);
}

.unit-hero .unit-hero__title {
  margin: 0 0 0.6rem;
  font-size: clamp(2rem, 4.6vw, 3.1rem);
  line-height: 1.08;
}

.unit-hero__blurb {
  margin: 0 0 1rem;
  max-width: 52ch;
  font-size: 1.1rem;
  line-height: 1.55;
  color: var(--pp-ink-soft);
}

.unit-hero__meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin: 0;
  padding: 0;
  list-style: none;
}
.unit-hero__meta li {
  margin: 0;
  padding: 0.3rem 0.75rem;
  border: 1px solid var(--pp-border);
  border-radius: 999px;
  background: var(--pp-fog);
  color: var(--pp-ink-soft);
  font-size: 0.85rem;
  font-weight: 600;
}

.unit-hero__row {
  display: flex;
  flex-direction: column;
  align-items: stretch;
  gap: 1rem;
  margin-top: 1.5rem;
}

.unit-hero__actions {
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}
.unit-hero__actions .btn { justify-content: center; text-align: center; }

/* The ring replaces lesson-progress.css's box and bar. */
.unit-hero .unit-progress.unit-ring {
  display: flex;
  align-items: center;
  gap: 0.9rem;
  margin: 0;
  padding: 0.5rem 1.1rem 0.5rem 0.5rem;
  max-width: none;
  border: 1px solid var(--pp-border);
  border-radius: 999px;
  background: var(--pp-paper);
}
.unit-hero .unit-progress.unit-ring[hidden] { display: none; }

.unit-hero .unit-ring__dial {
  position: relative;
  flex: none;
  display: grid;
  place-items: center;
  width: 60px;
  height: 60px;
  margin: 0;
  overflow: visible;
  border: 0;
  border-radius: 50%;
  background: none;
}
.unit-ring__svg {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  transform: rotate(-90deg);
}
.unit-ring__track,
.unit-ring__value {
  fill: none;
  stroke-width: 4;
}
.unit-ring__track { stroke: var(--pp-border); }
.unit-ring__value {
  stroke: var(--pp-line);
  stroke-linecap: round;
}
.unit-progress.is-complete .unit-ring__value { stroke: var(--success, #16a34a); }
.unit-hero .unit-ring .unit-progress__pct {
  position: relative;
  font-size: 0.95rem;
  font-weight: 800;
  color: var(--pp-ink);
}
.unit-hero .unit-ring .unit-progress__detail {
  max-width: 24ch;
  font-size: 0.88rem;
  line-height: 1.35;
  color: var(--pp-ink-soft);
}

/* ── the trail ────────────────────────────────────────────── */
.unit-lessons {
  min-width: 0;
  padding-top: 0.25rem;
}

.unit-lessons h2 { margin: 0 0 0.25rem; padding-top: 1.1rem; }
.unit-lessons .unit-lesson-summary { margin: 0 0 0.75rem; }

.unit-trail {
  margin: 1rem 0 0;
  padding: 0;
  list-style: none;
}

.unit-trail__stop {
  position: relative;
  margin: 0;
  padding: 0 0 0.85rem calc(var(--rail) * 2 + 18px);
}

/* The rail: each stop draws the segment down to the next one, so a finished
   lesson colours the path it has walked. */
.unit-trail__stop::before {
  content: "";
  position: absolute;
  left: calc(var(--rail) - 1.5px);
  top: 0;
  bottom: 0;
  width: 3px;
  background: var(--pp-border);
}
.unit-trail__stop:first-child::before { top: 28px; }
.unit-trail__stop--summit::before { bottom: auto; height: 28px; }
.unit-trail__stop.is-done::before { background: var(--pp-line); }

.unit-trail__num {
  position: absolute;
  z-index: 1;
  left: calc(var(--rail) - var(--dot) / 2);
  top: 8px;
  display: grid;
  place-items: center;
  width: var(--dot);
  height: var(--dot);
  box-sizing: border-box;
  border: 3px solid var(--pp-border);
  border-radius: 50%;
  background: var(--pp-paper);
  color: var(--pp-muted);
  font-weight: 800;
  font-size: 0.95rem;
  font-variant-numeric: tabular-nums;
}
.unit-trail__stop.is-started .unit-trail__num { border-color: var(--pp-line); color: var(--pp-ink); }
.unit-trail__stop.is-done .unit-trail__num {
  border-color: var(--pp-line);
  background: var(--pp-line);
  color: var(--pp-paper);
}
.unit-trail__stop.is-up-next .unit-trail__num {
  border-color: var(--pp-ink);
  background: var(--pp-ink);
  color: var(--pp-paper);
  box-shadow: 0 0 0 5px var(--pp-fog);
}
.unit-trail__num--summit {
  border-color: var(--pp-ink);
  background: var(--pp-fog);
  color: var(--pp-ink);
}

.unit-trail__card {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: center;
  gap: 0.35rem 1.25rem;
  min-height: 56px;
  padding: 0.95rem 1.15rem;
  border: 1px solid var(--pp-border);
  border-radius: 16px;
  background: var(--panel, var(--pp-paper));
  color: inherit;
  text-decoration: none;
}
a.unit-trail__card:hover {
  border-color: var(--pp-line);
  box-shadow: 0 6px 0 var(--pp-fog);
}
a.unit-trail__card:focus-visible {
  outline: 3px solid var(--pp-line);
  outline-offset: 3px;
}
.unit-trail__stop.is-up-next .unit-trail__card {
  border-color: var(--pp-ink);
  box-shadow: 0 6px 0 var(--pp-fog);
}

.unit-trail__body {
  display: flex;
  flex-direction: column;
  gap: 0.2rem;
  min-width: 0;
}
.unit-trail .unit-trail__title {
  margin: 0;
  font-size: 1.05rem;
  font-weight: 700;
  line-height: 1.3;
  color: var(--pp-ink);
}
.unit-trail__summary {
  margin: 0;
  font-size: 0.92rem;
  line-height: 1.45;
  color: var(--pp-ink-soft);
}

.unit-trail__meta {
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 0.35rem;
  white-space: nowrap;
}
.unit-trail__time {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--pp-ink-soft);
}
.unit-trail__status {
  padding: 0.15rem 0.6rem;
  border-radius: 999px;
  font-size: 0.78rem;
  font-weight: 700;
}
.unit-trail__status:empty { display: none; }
.is-done .unit-trail__status { background: var(--pp-fog); color: var(--pp-ink); }
.is-up-next .unit-trail__status { background: var(--pp-ink); color: var(--pp-paper); }
.is-started:not(.is-up-next) .unit-trail__status { border: 1px solid var(--pp-border); color: var(--pp-ink-soft); }

/* lesson-progress.js adds a tick inside each finished link; the status pill
   says the same thing in words, so the tick is not shown twice. */
.unit-trail .lesson-check { display: none; }

/* The summit: the end-of-unit test. */
.unit-trail__card--test {
  background: var(--pp-fog);
}
.unit-trail__card--test .unit-test-status { margin: 0.35rem 0 0; }
.unit-trail .unit-trail__test-link { white-space: nowrap; }

/* ── narrower screens: header on top, lessons below ──────── */
@media (max-width: 900px) {
  .unit-layout { grid-template-columns: minmax(0, 1fr); row-gap: 0.5rem; }
  .unit-hero { position: static; }
  .unit-hero__row { flex-direction: row; flex-wrap: wrap; align-items: center; gap: 1rem 1.75rem; }
  .unit-hero__actions { flex-direction: row; flex-wrap: wrap; }
  .unit-hero__actions .btn { justify-content: center; }
}

/* ── phones ───────────────────────────────────────────────── */
@media (max-width: 640px) {
  .unit-hero,
  .unit-lessons { --rail: 16px; --dot: 32px; }
  .unit-trail__stop { padding-left: calc(var(--rail) * 2 + 10px); }
  .unit-trail__num { top: 10px; font-size: 0.85rem; }
  .unit-trail__card {
    grid-template-columns: minmax(0, 1fr);
    padding: 0.85rem 0.95rem;
  }
  .unit-trail__meta {
    flex-direction: row;
    align-items: center;
    flex-wrap: wrap;
  }
  .unit-trail .unit-trail__test-link { justify-self: start; }
  .unit-hero .unit-progress.unit-ring { border-radius: 20px; }
}

/* ── motion ───────────────────────────────────────────────── */
@media (prefers-reduced-motion: no-preference) {
  /* No transform on the card, ever: a transform makes the card the positioning
     anchor for the number badge inside it, and the number jumps into the
     title on hover. The hover is border and shadow only. */
  a.unit-trail__card { transition: border-color 160ms ease, box-shadow 160ms ease; }
  .unit-ring__value { transition: stroke-dasharray 600ms cubic-bezier(.16, 1, .3, 1); }
}