:root {
  color-scheme: light dark;
  --bg: #f5f6fa;
  --fg: #222;
  --muted: #667;
  --surface: #fff;
  --surface-alt: #eef1f8;
  --surface-back: #eaf6ea;
  --border: #b9c0d4;
  --rule: #d5d9e5;
  --accent: #4a5db8;
  --accent-fg: #fff;
  --shadow: rgba(0, 0, 0, .08);
  --code-bg: #f2f3f7;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #14161c;
    --fg: #e8eaf0;
    --muted: #9aa3b8;
    --surface: #1e212b;
    --surface-alt: #2a2e3b;
    --surface-back: #1d2a22;
    --border: #3a4055;
    --rule: #333a4d;
    --accent: #7d8fe0;
    --accent-fg: #14161c;
    --shadow: rgba(0, 0, 0, .4);
    --code-bg: #23262f;
  }
}
* { box-sizing: border-box; }
body {
  font-family: system-ui, sans-serif;
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  min-height: 100vh;
}
.visually-hidden {
  position: absolute;
  width: 1px; height: 1px;
  margin: -1px; padding: 0; border: 0;
  clip: rect(0 0 0 0);
  clip-path: inset(50%);
  overflow: hidden;
  white-space: nowrap;
}
header h1 { font-size: 1.3rem; margin: 1.2rem 0; text-align: center; }
main { width: min(1000px, 94vw); margin: 0 auto; padding-bottom: 2rem; }
#start-area, #study-area { text-align: center; }
#deck-buttons { display: flex; flex-wrap: wrap; gap: .5rem; justify-content: center; }
button {
  font-size: 1rem;
  padding: .6rem 1.1rem;
  border: 1px solid var(--border);
  border-radius: .5rem;
  background: var(--surface);
  color: inherit;
  cursor: pointer;
}
button:hover:not(:disabled) { background: var(--surface-alt); }
button:disabled { opacity: .45; cursor: default; }
#deck-label { font-weight: 600; }
#counter { color: var(--muted); font-size: .9rem; margin: .25rem 0 1rem; }
#card {
  position: relative;
  width: 100%;
  min-height: 280px;
  perspective: 1200px;
  margin-bottom: 1rem;
}
.card-side {
  position: absolute;
  inset: 0;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  border-radius: 1rem;
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: .75rem;
  box-shadow: 0 4px 16px var(--shadow);
  transition: transform .5s;
  text-align: center;
}
.card-front { background: var(--surface); }
.card-back { background: var(--surface-back); transform: rotateY(180deg); }
#card.flipped .card-front { transform: rotateY(180deg); }
#card.flipped .card-back { transform: rotateY(0deg); }
.side-label { font-size: .75rem; letter-spacing: .15em; text-transform: uppercase; color: var(--muted); }
.card-front div, .card-back div { font-size: 1.15rem; line-height: 1.5; }
#controls { display: flex; gap: .5rem; justify-content: center; flex-wrap: wrap; }
#audio-toggle { margin-top: 1rem; }
#error { color: #e06060; text-align: center; font-weight: 600; }
#speed-panel {
  display: flex;
  gap: .4rem;
  justify-content: center;
  align-items: center;
  margin-top: 1rem;
  flex-wrap: wrap;
}
#speed-panel span { color: var(--muted); font-size: .9rem; }
.speed-btn { padding: .35rem .7rem; font-size: .9rem; }
.speed-btn.active { background: var(--accent); border-color: var(--accent); color: var(--accent-fg); }
#secondary-controls {
  display: flex;
  gap: .5rem;
  justify-content: center;
  flex-wrap: wrap;
  margin-top: 1rem;
}
#audio-toggle { margin-top: 0; }
#admin-open {
  margin-top: 1rem;
  font-size: 1.2rem;
  padding: .5rem .9rem;
}
#admin-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, .4);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 10;
}
#admin-overlay[hidden] { display: none; }
#admin-panel {
  background: var(--surface);
  border-radius: 1rem;
  padding: 1.5rem;
  width: min(480px, 92vw);
  max-height: 85vh;
  overflow: auto;
}
#admin-header { display: flex; justify-content: space-between; align-items: center; }
#admin-header h2 { margin: 0; font-size: 1.2rem; }
#admin-panel section { margin-top: 1.25rem; }
#admin-panel h3 { margin: 0 0 .5rem; font-size: 1rem; }
#admin-panel p { margin: .25rem 0 .75rem; color: var(--muted); font-size: .9rem; }
#admin-panel label { display: block; margin-top: .75rem; color: var(--fg); }
#admin-panel input {
  margin-left: .5rem; width: 5rem; padding: .3rem;
  background: var(--surface); color: inherit;
  border: 1px solid var(--border); border-radius: .3rem;
}
#convert-output {
  background: var(--code-bg);
  padding: .75rem;
  border-radius: .5rem;
  white-space: pre-wrap;
  font-size: .85rem;
  margin-top: .75rem;
  min-height: 1rem;
}
#study-layout {
  display: grid;
  grid-template-columns: 40fr 60fr;
  gap: 1rem;
  align-items: start;
}
#study-left { min-width: 0; }
#map-panel {
  background: var(--surface);
  border-radius: 1rem;
  padding: 1rem;
  box-shadow: 0 4px 16px var(--shadow);
  max-height: 75vh;
  overflow: auto;
  text-align: left;
}
#map-title { margin: 0 0 .75rem; font-size: 1rem; }
.map-node { margin: .1rem 0; }
.map-row { display: flex; gap: .4rem; align-items: flex-start; }
.map-toggle {
  background: none;
  border: none;
  cursor: pointer;
  padding: 0 .1rem;
  font-size: .8rem;
  color: var(--muted);
}
.map-title {
  font-size: .95rem;
  line-height: 1.4;
  white-space: pre-wrap;  /* le barre di frazione delle formule restano su righe proprie */
}
.map-children {
  margin-left: 1.1rem;
  border-left: 1px solid var(--rule);
  padding-left: .6rem;
}
.map-leaf .map-title { color: var(--muted); }
.map-leaf .map-title::before { content: '•'; color: var(--accent); margin-right: .35rem; }
.map-item .map-title { color: var(--fg); }
.map-ord {
  color: var(--accent);
  font-variant-numeric: tabular-nums;
  font-weight: 600;
  font-size: .9rem;
  min-width: 1.4rem;
  flex: none;
}
.map-placeholder { color: var(--muted); font-size: .9rem; }
@media (max-width: 900px) {
  #study-layout { grid-template-columns: 1fr; }
  #map-panel { max-height: 50vh; }
}

#keyboard-hint {
  text-align: center;
  color: var(--muted);
  font-size: .8rem;
  margin-top: 1.25rem;
}
#keyboard-hint kbd {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: .25rem;
  padding: .05rem .35rem;
  font-family: inherit;
  font-size: .8rem;
}
:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}
@media (max-width: 900px) {
  #keyboard-hint { display: none; }
}