/* The course: the hub, topic and lesson pages, and the trainers. One stage layout serves every trainer: the board, and beside it
   (below it on a phone) a panel with the instruction, the feedback and the actions, so the eye always finds them in one place. */

.learn { display: grid; gap: clamp(1.25rem, 4vw, 2rem); padding-bottom: clamp(2rem, 8vw, 4rem); }
.learn-heading { max-width: 46rem; padding-top: clamp(0.25rem, 2vw, 1.5rem); }
.learn-heading h1 { margin-bottom: 0.5rem; font-size: clamp(1.8rem, 7vw, 3.2rem); letter-spacing: -0.045em; line-height: 1.04; }
.learn-heading.compact h1 { font-size: clamp(1.6rem, 6vw, 2.4rem); }
.learn-players { margin: 0.35rem 0 0; color: var(--ink-muted); font-size: 0.86rem; }
.learn-lead { max-width: 44rem; margin-bottom: 0; color: var(--ink-muted); font-size: clamp(0.92rem, 3.4vw, 1.05rem); line-height: 1.55; }
.learn-section { display: grid; gap: 0.9rem; }
.learn-section > h2, .learn-review > h2, .learn-sync > h2 { margin: 0; font-size: clamp(1.2rem, 4.5vw, 1.5rem); letter-spacing: -0.03em; }
.learn-credits { max-width: 46rem; margin: 0; color: var(--ink-muted); font-size: 0.78rem; }
.learn-credits a { text-underline-offset: 0.2em; }

/* The trainer is rendered by the browser; until it is, the server's preview stands in its place. An element holding only the
   trainer's marker comment is empty, so the preview hides itself the moment the trainer has drawn anything. */
.learn-live:empty { display: none; }
.learn-live:not(:empty) + .learn-static { display: none; }

.learn-cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(15rem, 1fr)); gap: 0.75rem; margin: 0; padding: 0; list-style: none; }
.learn-card { min-height: 100%; display: grid; align-content: start; gap: 0.35rem; padding: 1.05rem 1.15rem; color: var(--ink); border-radius: var(--radius-surface); background: var(--surface); text-decoration: none; transition: background 140ms ease; }
.learn-card-icon { color: var(--accent); font-size: 1.5rem; line-height: 1; }
/* A trainer card is one row: the piece glyph beside the name and a one-line purpose. */
.learn-card:has(> .learn-card-icon) { grid-template-columns: 1.75rem minmax(0, 1fr); column-gap: 0.75rem; row-gap: 0.1rem; align-items: center; padding-block: 0.8rem; }
.learn-card:has(> .learn-card-icon) > .learn-card-icon { grid-row: span 2; align-self: center; }
.learn-card:has(> .learn-card-icon) > .learn-card-text { font-size: 0.78rem; line-height: 1.4; }
.learn-cards:has(> li > .learn-card > .learn-card-icon) { gap: 0.5rem; }
.learn-card-title, .learn-card h3 { margin: 0; font-size: 1rem; font-weight: 720; letter-spacing: -0.02em; }
.learn-card h3 a { text-decoration: none; }
.learn-card h3 a::after { content: " →"; color: var(--accent); }
.learn-card-text { margin: 0; color: var(--ink-muted); font-size: 0.82rem; }
.learn-card-meta { color: var(--accent-ink); font-size: 0.72rem; font-variant-numeric: tabular-nums; }
.learn-lesson-links { display: flex; flex-wrap: wrap; gap: 0.4rem; margin: 0.35rem 0 0; padding: 0; list-style: none; font-size: 0.78rem; }
.learn-lesson-links a { min-height: 36px; display: inline-flex; align-items: center; padding: 0 0.55rem; color: var(--ink); border-radius: var(--radius-pill); background: var(--surface-subtle); text-decoration: none; }

/* Hub dashboard. */
.learn-dashboard { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 0.6rem; }
.learn-tile { display: grid; align-content: start; gap: 0.15rem; padding: 0.9rem 1rem; color: var(--ink); border-radius: var(--radius-surface); background: var(--surface); text-decoration: none; transition: background 140ms ease; }
.learn-tile.attention { box-shadow: inset 0 0 0 1px var(--accent); }
.learn-stat { display: grid; align-content: start; gap: 0.1rem; }
.learn-stat-label { color: var(--ink-muted); font-size: 0.68rem; font-weight: 700; letter-spacing: 0.08em; text-transform: uppercase; }
.learn-stat-value { font-size: clamp(1.4rem, 6vw, 1.9rem); font-variant-numeric: tabular-nums; font-weight: 760; letter-spacing: -0.04em; line-height: 1.1; }
.learn-stat-value.low { color: var(--danger); }
.learn-stat-of { margin-inline-start: 0.2em; color: var(--ink-muted); font-size: 0.6em; font-weight: 600; }
.learn-stat-note { color: var(--ink-muted); font-size: 0.74rem; overflow-wrap: anywhere; }
.learn-delta { width: fit-content; padding: 0.05rem 0.45rem; border-radius: var(--radius-pill); font-size: 0.74rem; font-variant-numeric: tabular-nums; font-weight: 700; animation: learn-pop 260ms cubic-bezier(0.2, 0, 0, 1) both; }
.learn-delta.up { color: var(--accent-ink); background: var(--accent-soft); }
.learn-delta.down { color: var(--danger); background: var(--danger-soft); }
.learn-warning { margin: 0; padding: 0.75rem 1rem; color: var(--ink); border-radius: var(--radius-surface); background: var(--danger-soft); font-size: 0.86rem; }

.learn-review, .learn-sync { display: grid; gap: 0.75rem; padding: clamp(1rem, 4vw, 1.5rem); border-radius: var(--radius-surface); background: var(--surface); }
.learn-review p, .learn-sync p { margin: 0; color: var(--ink-muted); font-size: 0.86rem; }
.learn-review-list { display: grid; gap: 0.4rem; margin: 0; padding: 0; list-style: none; }
.learn-review-list a { min-height: 44px; display: flex; align-items: center; justify-content: space-between; gap: 1rem; padding: 0 0.85rem; color: var(--ink); border-radius: var(--radius-control); background: var(--surface-subtle); text-decoration: none; }
.learn-badge { min-width: 1.6rem; padding: 0.1rem 0.5rem; color: var(--on-accent); border-radius: var(--radius-pill); background: var(--accent); font-size: 0.7rem; font-variant-numeric: tabular-nums; font-weight: 760; text-align: center; }
.learn-callout { display: grid; gap: 0.6rem; padding: 0.9rem 1rem; border-radius: var(--radius-control); box-shadow: inset 0 0 0 1px var(--accent); background: var(--accent-soft); }
.learn-callout p { color: var(--accent-ink); }
.learn-sync-state { font-size: 0.8rem; }

/* Topic progress. */
.learn-topic-progress { display: grid; gap: 0.9rem; justify-items: start; }
.learn-meter { width: 100%; height: 0.45rem; appearance: none; border: 0; border-radius: var(--radius-pill); background: var(--surface-subtle); overflow: hidden; }
.learn-meter::-webkit-progress-bar { border-radius: var(--radius-pill); background: var(--surface-subtle); }
.learn-meter::-webkit-progress-value { border-radius: var(--radius-pill); background: var(--accent); transition: inline-size 300ms ease; }
.learn-meter::-moz-progress-bar { border-radius: var(--radius-pill); background: var(--accent); }
.learn-topic-marks { width: 100%; display: grid; gap: 0.4rem; margin: 0; padding: 0; list-style: none; counter-reset: lesson; }
.learn-topic-marks a { min-height: 52px; display: flex; align-items: center; justify-content: space-between; gap: 1rem; padding: 0 1rem; color: var(--ink); border-radius: var(--radius-control); background: var(--surface); text-decoration: none; counter-increment: lesson; }
.learn-topic-marks a > span:first-child::before { content: counter(lesson) ". "; color: var(--ink-muted); font-variant-numeric: tabular-nums; }

/* Stars. */
.learn-stars { display: flex; gap: 0.25rem; margin: 0; color: var(--line-strong); font-size: 2.2rem; line-height: 1; }
.learn-stars.small { gap: 0.1rem; font-size: 0.95rem; }
.learn-stars .earned { color: #f2c14e; }
.learn-complete .learn-stars .earned { animation: learn-star 420ms cubic-bezier(0.2, 0, 0, 1.4) both; }
.learn-complete .learn-stars .earned:nth-child(2) { animation-delay: 120ms; }
.learn-complete .learn-stars .earned:nth-child(3) { animation-delay: 240ms; }

/* The trainer stage. */
.learn-stage { display: grid; gap: 1rem; align-items: start; }
.learn-board-column { width: min(100%, calc(100svh - 11rem), 40rem); min-width: 0; justify-self: center; }
.learn-panel { display: grid; gap: 0.85rem; align-content: start; min-width: 0; padding: clamp(1rem, 4vw, 1.35rem); border-radius: var(--radius-surface); background: var(--surface); }
.learn-panel .eyebrow, .learn-panel > .field, .learn-sync > .field { margin: 0; }
.learn-instruction { margin: 0; font-size: clamp(1.1rem, 4.4vw, 1.35rem); font-weight: 720; letter-spacing: -0.025em; line-height: 1.25; }
.learn-counter { margin: 0; color: var(--ink-muted); font-size: 0.8rem; font-variant-numeric: tabular-nums; }
.learn-feedback { min-height: 1.5em; margin: 0; padding-inline-start: 0.75rem; border-inline-start: 3px solid transparent; font-size: 0.92rem; line-height: 1.45; }
.learn-feedback:empty { padding: 0; border: 0; }
.learn-feedback.good, .learn-feedback.success { color: var(--accent-ink); border-color: var(--accent); }
.learn-feedback.success { font-weight: 650; }
.learn-feedback.warning { color: #f2c14e; border-color: #f2c14e; }
.learn-feedback.error { color: var(--danger); border-color: var(--danger); }
.learn-feedback.hint { color: var(--focus); border-color: var(--focus); }
.learn-feedback.info { color: var(--ink-muted); border-color: var(--line-strong); }
.learn-feedback:not(:empty) { animation: learn-fade 180ms ease both; }
.learn-actions { display: flex; flex-wrap: wrap; align-items: center; gap: 0.5rem 0.75rem; }
.learn-scoreboard { display: flex; flex-wrap: wrap; gap: 1.25rem; }
.learn-steps { display: flex; gap: 0.35rem; margin: 0; padding: 0; list-style: none; }
.learn-steps li { width: 1.5rem; height: 0.35rem; border-radius: var(--radius-pill); background: var(--surface-subtle); transition: background 200ms ease; }
.learn-steps li.current { background: var(--accent-hover); box-shadow: 0 0 0 2px var(--accent-soft); }
.learn-steps li.done { background: var(--accent); }
.learn-complete { display: grid; gap: 0.6rem; }
.learn-complete h2 { margin: 0; font-size: clamp(1.4rem, 5vw, 1.8rem); letter-spacing: -0.03em; }
.learn-complete p { margin: 0; color: var(--ink-muted); }
.learn-principles { display: grid; gap: 0.3rem; margin: 0; padding: 0; list-style: none; font-size: 0.84rem; }
.learn-principles li { display: flex; gap: 0.5rem; }
.learn-principles .kept > span:first-child { color: var(--accent); }
.learn-principles .broken { color: var(--danger); }
.learn-plan { display: grid; gap: 0.35rem; margin: 0; padding-inline-start: 1.2rem; color: var(--ink-muted); font-size: 0.84rem; }
.learn-line { margin: 0; color: var(--ink-muted); font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-size: 0.82rem; overflow-wrap: anywhere; }
.learn-facts { display: grid; gap: 0.4rem; margin: 0; font-size: 0.8rem; }
.learn-facts div { display: grid; grid-template-columns: 5rem minmax(0, 1fr); gap: 0.5rem; }
.learn-facts dt { color: var(--ink-muted); }
.learn-facts dd { display: flex; flex-wrap: wrap; gap: 0.3rem; margin: 0; }
.learn-chip { min-height: 28px; display: inline-flex; align-items: center; padding: 0 0.55rem; color: var(--ink); border-radius: var(--radius-pill); background: var(--surface-subtle); font-size: 0.74rem; text-decoration: none; }
.learn-scoring, .learn-hint { margin: 0; color: var(--ink-muted); font-size: 0.74rem; }
.learn-loading { margin: 0; padding: 2rem 0; color: var(--ink-muted); text-align: center; }
.learn-panel .learn-loading { padding: 0; text-align: start; }
.learn-best strong { color: var(--ink); }

/* Typed answers. */
.learn-entry-row { display: flex; gap: 0.5rem; }
.learn-entry-row input { min-width: 0; flex: 1; }
.learn-sync .learn-entry-row input { font-family: ui-monospace, SFMono-Regular, Menlo, monospace; }
.learn-position-text { display: grid; gap: 0.45rem; margin: 0; font-size: 0.9rem; }
.learn-position-text div { display: grid; grid-template-columns: 5rem minmax(0, 1fr); gap: 0.5rem; }
.learn-position-text dt { color: var(--ink-muted); font-weight: 650; }
.learn-position-text dd { margin: 0; }
.learn-blindfold { aspect-ratio: 1; display: grid; place-content: center; justify-items: center; gap: 0.75rem; padding: 2rem; color: var(--ink-muted); border-radius: var(--radius-surface); background: var(--surface); text-align: center; }
.learn-blindfold span { color: var(--accent); font-size: 3rem; }

/* The lesson pager. */
.learn-pager { display: flex; justify-content: space-between; gap: 1rem; font-size: 0.86rem; }
.learn-pager a { min-height: 44px; display: inline-flex; align-items: center; gap: 0.4rem; color: var(--ink-muted); text-decoration: none; }

@keyframes learn-fade { from { opacity: 0; translate: 0 2px; } }
@keyframes learn-pop { from { opacity: 0; scale: 0.8; } }
@keyframes learn-star { from { opacity: 0; scale: 0.3; rotate: -30deg; } }

@media (hover: hover) {
  .learn-card:hover, .learn-tile:hover { background: var(--surface-subtle); }
  .learn-review-list a:hover, .learn-topic-marks a:hover, .learn-lesson-links a:hover, .learn-chip:hover { background: var(--line); }
  .learn-pager a:hover { color: var(--ink); }
}

/* Phones: the trail and the mode tabs take one row each, so the board and its instruction come into view sooner. */
@media (max-width: 34.999rem) {
  .learn { gap: 1rem; }
  .learn .wide-only, .learn > .breadcrumbs:has(+ .learn-heading .tab-links) { display: none; }
  /* Once a trainer is running, its title and mode tabs say enough; the clock and instruction under the board stay in view. */
  .learn:has(> .learn-live:not(:empty)) .learn-heading.compact .learn-lead { display: none; }
  .learn-heading.compact h1 { margin-bottom: 0; font-size: 1.6rem; }
  /* The hidden board is a reminder, not a board: on a phone it shrinks to one line so the piece lists are in view. */
  .learn-blindfold { aspect-ratio: auto; grid-auto-flow: column; gap: 0.6rem; padding: 0.85rem 1rem; }
  .learn-blindfold span { font-size: 1.5rem; }
  .learn .tab-links { flex-wrap: nowrap; margin-block: 0.75rem 0; overflow-x: auto; scrollbar-width: none; }
  .learn .tab-links::-webkit-scrollbar { display: none; }
  .learn .tab-links a { flex: 0 0 auto; padding-inline: 0.8rem; font-size: 0.8rem; }
}

@media (min-width: 40rem) {
  .learn-dashboard { grid-template-columns: repeat(4, minmax(0, 1fr)); }
}

@media (min-width: 60rem) {
  .learn-stage { grid-template-columns: minmax(0, 1fr) minmax(19rem, 24rem); }
  .learn-board-column { justify-self: stretch; width: min(100%, calc(100svh - 9rem)); }
  .learn-panel { position: sticky; top: 1rem; }
}

@media (prefers-reduced-motion: reduce) {
  .learn-feedback:not(:empty), .learn-delta, .learn-complete .learn-stars .earned { animation: none; }
  .learn-meter::-webkit-progress-value, .learn-steps li { transition: none; }
}