/* learn.ifs.name — mobile first, light/dark via custom properties */

:root {
  color-scheme: light;
  --bg: #f7f5f0;
  --surface: #ffffff;
  --surface-2: #efece4;
  --text: #1f1d1a;
  --muted: #6b665d;
  --border: #dcd7cc;
  --accent: #2f5d8a;
  --accent-text: #ffffff;
  --know: #2e7d4f;
  --know-bg: #e6f2ea;
  --again: #a3620a;
  --again-bg: #fbf0dd;
  --danger: #b3261e;
  --focus: #2f5d8a;
  --shadow: 0 1px 2px rgba(31, 29, 26, .06), 0 4px 16px rgba(31, 29, 26, .06);

  --font-ui: "IBM Plex Sans", system-ui, -apple-system, "Segoe UI", sans-serif;
  --font-text: "Source Serif 4", Georgia, "Times New Roman", serif;
  --radius: 12px;
  --gutter: 16px;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    color-scheme: dark;
    --bg: #161514;
    --surface: #211f1d;
    --surface-2: #2b2926;
    --text: #ece8e1;
    --muted: #a39d93;
    --border: #3a3733;
    --accent: #8db8e3;
    --accent-text: #10161c;
    --know: #7fcf9d;
    --know-bg: #1d3226;
    --again: #e8b562;
    --again-bg: #3a2c15;
    --danger: #f2948d;
    --focus: #8db8e3;
    --shadow: 0 1px 2px rgba(0, 0, 0, .4), 0 4px 16px rgba(0, 0, 0, .25);
  }
}

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

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-ui);
  font-size: 16px;
  line-height: 1.5;
}

a { color: var(--accent); }
a:hover { text-decoration-thickness: 2px; }

:focus-visible { outline: 2px solid var(--focus); outline-offset: 2px; }

.visually-hidden {
  position: absolute; width: 1px; height: 1px; overflow: hidden;
  clip: rect(0 0 0 0); white-space: nowrap;
}

/* ---- frame ------------------------------------------------------------ */

.site-header,
.page {
  max-width: 44rem;
  margin: 0 auto;
  padding: 0 var(--gutter);
}

.site-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  min-height: 60px;
}

.site-name {
  font-weight: 600;
  letter-spacing: .01em;
  color: var(--text);
  text-decoration: none;
  padding: 10px 0;
}

.page { padding-bottom: 48px; }

h1 {
  font-family: var(--font-text);
  font-weight: 600;
  font-size: 1.75rem;
  line-height: 1.2;
  margin: 8px 0 8px;
}

h2 { font-size: 1.05rem; margin: 32px 0 12px; }

.lede, .status { color: var(--muted); }

/* ---- catalog ---------------------------------------------------------- */

.group-title {
  font-size: .8rem;
  text-transform: uppercase;
  letter-spacing: .08em;
  color: var(--muted);
  font-weight: 600;
}

.catalog-list { list-style: none; margin: 0; padding: 0; display: grid; gap: 12px; }

.catalog-entry {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}
.catalog-entry:hover { border-color: var(--accent); }
.catalog-entry .early-access { padding: 0 16px 16px; }

.catalog-link {
  display: block;
  padding: 16px;
  color: var(--text);
  text-decoration: none;
}

.catalog-title {
  display: block;
  font-family: var(--font-text);
  font-size: 1.2rem;
  font-weight: 600;
  line-height: 1.3;
}

.catalog-meta { display: block; margin-top: 4px; font-size: .875rem; color: var(--muted); }

.tagline {
  font-family: var(--font-text);
  font-size: 1.2rem;
  line-height: 1.35;
  margin: 0 0 16px;
}
.cta { margin-bottom: 12px; }

/* ---- subscribe -------------------------------------------------------- */

.subscribe-btn {
  min-height: 44px;
  padding: 8px 16px;
  font: inherit;
  font-weight: 600;
  color: var(--accent-text);
  background: var(--accent);
  border: 1px solid var(--accent);
  border-radius: 999px;
  cursor: pointer;
  white-space: nowrap;
}
.subscribe-btn:hover { filter: brightness(1.08); }
.subscribe-btn.header { font-size: .85rem; padding: 6px 14px; }
.subscribe-btn.large { font-size: 1.05rem; padding: 10px 22px; min-height: 48px; }
.subscribe-btn.small {
  font-size: .8rem;
  color: var(--accent);
  background: transparent;
}

.early-access {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  margin: 0 0 16px;
}
.catalog-entry .early-access { margin: 0; }

.badge {
  display: inline-block;
  padding: 3px 10px;
  border-radius: 999px;
  font-size: .78rem;
  font-weight: 500;
  line-height: 1.35;
}
.badge-early { color: var(--again); background: var(--again-bg); }

.dialog {
  width: min(28rem, calc(100vw - 2 * var(--gutter)));
  padding: 0;
  color: var(--text);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: 0 12px 48px rgba(0, 0, 0, .3);
}
.dialog::backdrop { background: rgba(0, 0, 0, .45); }
/* fallback when showModal is unavailable */
.dialog[open]:not(:modal) {
  position: fixed; inset: 0; margin: auto; height: fit-content; z-index: 10;
}
.dialog-inner { position: relative; padding: 24px 20px 20px; }
.dialog h2 {
  font-family: var(--font-text);
  font-size: 1.25rem;
  margin: 0 40px 12px 0;
}
.dialog p { margin: 0; }
.dialog-close {
  position: absolute;
  top: 8px;
  right: 8px;
  width: 44px;
  height: 44px;
  font-size: 1.5rem;
  line-height: 1;
  color: var(--muted);
  background: none;
  border: 0;
  border-radius: 8px;
  cursor: pointer;
}

/* ---- study ------------------------------------------------------------ */

.deck-refs { margin: 0 0 16px; font-size: .875rem; color: var(--muted); }
.deck-refs a, .citations a, .bib a { color: inherit; }

.controls { display: grid; gap: 8px; margin-bottom: 12px; }

.section-select select {
  width: 100%;
  min-height: 44px;
  padding: 8px 12px;
  font: inherit;
  color: var(--text);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
}

.toggles { display: flex; gap: 8px; }

.toggle {
  flex: 1;
  min-height: 44px;
  padding: 8px 12px;
  font: inherit;
  font-size: .9rem;
  color: var(--text);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
}
.toggle[aria-pressed="true"] {
  background: var(--accent);
  border-color: var(--accent);
  color: var(--accent-text);
}

@media (min-width: 600px) {
  .controls { grid-template-columns: 1fr auto; align-items: center; }
  .toggle { flex: 0 0 auto; }
}

.progress-row {
  display: flex;
  justify-content: space-between;
  font-size: .85rem;
  color: var(--muted);
  font-variant-numeric: tabular-nums;
}

.progress {
  height: 4px;
  margin: 6px 0 16px;
  background: var(--surface-2);
  border-radius: 2px;
  overflow: hidden;
}
.progress-fill { height: 100%; background: var(--accent); transition: width .2s ease; }

.card {
  position: relative;
  min-height: 15rem;
  padding: 20px 16px 16px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  cursor: pointer;
  overflow-wrap: anywhere;
  user-select: text;
}
.card.mark-know { border-color: var(--know); }
.card.mark-again { border-color: var(--again); }

@media (min-width: 600px) { .card { padding: 28px 28px 20px; } }

.card-section { font-size: .8rem; color: var(--muted); margin-bottom: 12px; padding-right: 7rem; }

.card-front,
.card-back {
  font-family: var(--font-text);
  font-size: 1.25rem;
  line-height: 1.45;
}

.card-back-wrap {
  margin-top: 16px;
  padding-top: 16px;
  border-top: 1px solid var(--border);
}
.card-back { font-size: 1.1rem; }

.card-hint { margin-top: 24px; font-size: .85rem; color: var(--muted); }

.card .katex { font-size: 1.05em; }
.card .katex-display { overflow-x: auto; overflow-y: hidden; }

.mark-badge {
  position: absolute;
  top: 14px;
  right: 14px;
  padding: 2px 10px;
  border-radius: 999px;
  font-size: .75rem;
  font-weight: 600;
}
.mark-know .mark-badge { color: var(--know); background: var(--know-bg); }
.mark-again .mark-badge { color: var(--again); background: var(--again-bg); }

.citations {
  list-style: none;
  margin: 16px 0 0;
  padding: 0;
  font-size: .8rem;
  line-height: 1.4;
  color: var(--muted);
}

.card.done { cursor: default; display: grid; place-content: center; text-align: center; }
.done-title { font-family: var(--font-text); font-size: 1.3rem; font-weight: 600; margin: 0; }

.actions {
  display: grid;
  grid-template-columns: 48px 1fr 1fr 48px;
  gap: 8px;
  margin-top: 12px;
}

.btn {
  min-height: 44px;
  padding: 8px 14px;
  font: inherit;
  font-weight: 500;
  color: var(--text);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
}
.btn:disabled { opacity: .45; cursor: default; }
.btn.nav { padding: 0; font-size: 1.2rem; }
.btn.know { color: var(--know); border-color: var(--know); background: var(--know-bg); }
.btn.again { color: var(--again); border-color: var(--again); background: var(--again-bg); }
.btn.primary { color: var(--accent-text); background: var(--accent); border-color: var(--accent); margin-top: 8px; }
.btn.danger { color: var(--danger); border-color: var(--danger); }
.btn.subtle { border-color: transparent; background: none; color: var(--muted); padding-left: 0; }

.key-hint { margin: 14px 0 0; font-size: .8rem; color: var(--muted); text-align: center; }
kbd {
  font-family: var(--font-ui);
  font-size: .75rem;
  padding: 1px 6px;
  border: 1px solid var(--border);
  border-bottom-width: 2px;
  border-radius: 4px;
  background: var(--surface);
}
@media (max-width: 599px), (hover: none) { .key-hint { display: none; } }

.deck-footer { margin-top: 24px; }
.confirm { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; font-size: .9rem; }

.bibliography { margin-top: 24px; font-size: .9rem; color: var(--muted); }
.bibliography h2 { color: var(--text); }
.bibliography ul { margin: 0; padding-left: 1.2em; }
.bib a { overflow-wrap: anywhere; }

/* ---- prerendered (no-JS) deck listing ---------------------------------- */

.static-section h2 { font-family: var(--font-text); font-size: 1.25rem; }
.static-cards { margin: 0; padding: 0; list-style: none; display: grid; gap: 12px; }
.static-card {
  padding: 16px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
}
.static-card .card-front { font-weight: 600; font-size: 1.1rem; }
.static-card .card-back { margin-top: 8px; font-size: 1.05rem; }

/* ---- footer / help ----------------------------------------------------- */

.site-footer {
  max-width: 44rem;
  margin: 0 auto;
  padding: 0 var(--gutter) 32px;
  font-size: .875rem;
  color: var(--muted);
}
.site-footer a { color: inherit; display: inline-block; padding: 12px 0; }

.help { max-width: 38rem; }
.faq h2 { font-family: var(--font-text); font-size: 1.15rem; margin: 28px 0 8px; }
.faq p { margin: 0 0 10px; }