/* =========================================================
   Grandezze Fisiche — Foglio di stile
   Tema chiaro (giorno) e scuro (notte) tramite variabili CSS
   ========================================================= */

:root {
  /* --- Tema chiaro (giorno) --- */
  --bg: #f4f7fb;
  --bg-soft: #e9eef6;
  --surface: #ffffff;
  --surface-2: #f7f9fc;
  --text: #14213d;
  --text-soft: #4a5568;
  --border: #dbe3ee;
  --primary: #2563eb;
  --primary-strong: #1d4ed8;
  --primary-soft: #dbeafe;
  --accent: #0891b2;
  --success: #16a34a;
  --success-soft: #dcfce7;
  --error: #dc2626;
  --error-soft: #fee2e2;
  --highlight: #fff8e6;
  --highlight-border: #f6d67a;
  --shadow: 0 6px 24px rgba(20, 33, 61, 0.08);
  --shadow-sm: 0 2px 8px rgba(20, 33, 61, 0.06);
  --radius: 16px;
  --radius-sm: 10px;
  --font: "Segoe UI", system-ui, -apple-system, Roboto, Helvetica, Arial, sans-serif;
}

html[data-theme="dark"] {
  /* --- Tema scuro (notte) --- */
  --bg: #0e1526;
  --bg-soft: #131c30;
  --surface: #182236;
  --surface-2: #1f2b42;
  --text: #eaf0fb;
  --text-soft: #a9b6cc;
  --border: #2b3a55;
  --primary: #60a5fa;
  --primary-strong: #93c5fd;
  --primary-soft: #1e3a5f;
  --accent: #22d3ee;
  --success: #4ade80;
  --success-soft: #14331f;
  --error: #f87171;
  --error-soft: #3a1518;
  --highlight: #2a2410;
  --highlight-border: #6b5a1e;
  --shadow: 0 6px 24px rgba(0, 0, 0, 0.4);
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  transition: background 0.3s ease, color 0.3s ease;
}

.skip-link {
  position: absolute;
  left: -999px;
  top: 0;
  background: var(--primary);
  color: #fff;
  padding: 0.6rem 1rem;
  border-radius: 0 0 var(--radius-sm) 0;
  z-index: 100;
}
.skip-link:focus { left: 0; }

/* ---------------- Header / navigazione ---------------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  display: flex;
  align-items: center;
  gap: 1rem;
  flex-wrap: wrap;
  padding: 0.7rem 1.2rem;
  background: color-mix(in srgb, var(--surface) 88%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-weight: 800;
  font-size: 1.15rem;
  letter-spacing: -0.01em;
}
.brand-logo { font-size: 1.5rem; }

.main-nav {
  display: flex;
  gap: 0.3rem;
  flex-wrap: wrap;
  flex: 1;
  justify-content: center;
}

.tab-btn {
  border: none;
  background: transparent;
  color: var(--text-soft);
  font-family: inherit;
  font-size: 0.95rem;
  font-weight: 600;
  padding: 0.5rem 0.85rem;
  border-radius: 999px;
  cursor: pointer;
  transition: all 0.2s ease;
  white-space: nowrap;
}
.tab-btn:hover { background: var(--bg-soft); color: var(--text); }
.tab-btn.is-active { background: var(--primary); color: #fff; }

.theme-toggle {
  border: 1px solid var(--border);
  background: var(--surface-2);
  width: 44px;
  height: 44px;
  border-radius: 50%;
  cursor: pointer;
  font-size: 1.25rem;
  display: grid;
  place-items: center;
  transition: transform 0.2s ease, background 0.2s ease;
}
.theme-toggle:hover { transform: rotate(20deg) scale(1.05); }

/* ---------------- Layout sezioni ---------------- */
main {
  max-width: 900px;
  margin: 0 auto;
  padding: 2rem 1.2rem 4rem;
}

.tab-panel { display: none; animation: fadeIn 0.35s ease; }
.tab-panel.is-active { display: block; }

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ---------------- Sottoschede ---------------- */
.subnav {
  display: flex;
  gap: 0.4rem;
  flex-wrap: wrap;
  margin: 0 0 1.3rem;
  padding: 0.35rem;
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 999px;
}
.subnav-btn {
  border: none;
  background: transparent;
  color: var(--text-soft);
  font-family: inherit;
  font-size: 0.92rem;
  font-weight: 600;
  padding: 0.5rem 0.95rem;
  border-radius: 999px;
  cursor: pointer;
  transition: all 0.18s ease;
  flex: 1;
  min-width: max-content;
  white-space: nowrap;
}
.subnav-btn:hover { color: var(--text); background: var(--bg-soft); }
.subnav-btn.is-active { background: var(--primary); color: #fff; }

.sub-panel { display: none; animation: fadeIn 0.3s ease; }
.sub-panel.is-active { display: block; }

h1 {
  font-size: clamp(1.6rem, 4vw, 2.3rem);
  line-height: 1.2;
  margin: 0 0 0.6rem;
  letter-spacing: -0.02em;
}
h2 {
  font-size: 1.3rem;
  margin: 0 0 0.7rem;
  letter-spacing: -0.01em;
}
.lead {
  font-size: 1.1rem;
  color: var(--text-soft);
  max-width: 65ch;
  margin: 0 0 1.5rem;
}
.hl { color: var(--primary); }

/* ---------------- Card ---------------- */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  margin-bottom: 1.5rem;
  box-shadow: var(--shadow-sm);
}
.highlight-card {
  background: var(--highlight);
  border-color: var(--highlight-border);
}
html[data-theme="dark"] .highlight-card { background: var(--surface-2); }

.hero { margin-bottom: 1.5rem; }

.note {
  font-size: 0.92rem;
  color: var(--text-soft);
  background: var(--surface-2);
  border-left: 3px solid var(--accent);
  padding: 0.6rem 0.9rem;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  margin: 1rem 0 0;
}

/* ---------------- Esempio di misura ---------------- */
.measure-example {
  display: flex;
  align-items: baseline;
  justify-content: center;
  gap: 0.4rem;
  font-weight: 800;
  margin: 1rem 0 0.3rem;
}
.measure-number { font-size: 3rem; color: var(--primary); }
.measure-unit { font-size: 2rem; color: var(--accent); }
.measure-labels {
  display: flex;
  justify-content: space-between;
  font-size: 0.85rem;
  color: var(--text-soft);
  max-width: 320px;
  margin: 0 auto;
}

/* ---------------- Tabelle ---------------- */
.table-scroll { overflow-x: auto; margin: 0.5rem 0; }
.data-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.95rem;
  min-width: 320px;
}
.data-table th, .data-table td {
  text-align: left;
  padding: 0.55rem 0.8rem;
  border-bottom: 1px solid var(--border);
}
.data-table th {
  background: var(--surface-2);
  font-weight: 700;
}
.data-table tbody tr:hover { background: var(--surface-2); }

.prefix-table .tier-up td:first-child { color: var(--primary); font-weight: 600; }
.prefix-table .tier-down td:first-child { color: var(--accent); font-weight: 600; }
.prefix-table .tier-base { background: var(--primary-soft); }

/* ---------------- Liste / steps ---------------- */
.steps, .rule-list { margin: 0.5rem 0; padding-left: 1.3rem; }
.steps li, .rule-list li { margin-bottom: 0.5rem; }

/* ---------------- Esempi svolti ---------------- */
.worked {
  background: var(--surface-2);
  border-radius: var(--radius-sm);
  padding: 0.9rem 1.1rem;
  margin: 1rem 0 0;
}
.worked-title { margin: 0 0 0.4rem; }
.worked-result {
  font-weight: 700;
  color: var(--success);
  margin: 0.4rem 0 0;
}

/* ---------------- Formula box ---------------- */
.formula-box {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.3rem;
  font-size: 1.3rem;
  background: var(--surface-2);
  border-radius: var(--radius-sm);
  padding: 1rem 1.2rem;
  margin: 0.6rem 0;
}
.frac { display: inline-flex; flex-direction: column; text-align: center; vertical-align: middle; }
.frac-top { border-bottom: 2px solid currentColor; padding: 0 0.4rem; }
.frac-bot { padding: 0 0.4rem; }

/* ---------------- Confronto dimensioni ---------------- */
.compare-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.8rem;
  text-align: center;
  margin: 0.5rem 0;
}
.compare-item {
  background: var(--surface-2);
  border-radius: var(--radius-sm);
  padding: 1rem 0.5rem;
}
.compare-big {
  display: block;
  font-size: 1.8rem;
  font-weight: 800;
  color: var(--primary);
  margin-bottom: 0.3rem;
}

/* ---------------- Convertitore interattivo ---------------- */
.converter { margin-top: 0.5rem; margin-bottom: 0.5rem; }
.converter-subtitle { font-size: 1rem; margin: 1.2rem 0 0.2rem; color: var(--accent); }
.converter-category { max-width: 260px; margin-bottom: 0.9rem; }
.converter-note {
  margin: 0.9rem 0 0.6rem;
  font-size: 0.95rem;
  color: var(--text);
  background: var(--surface-2);
  border-left: 3px solid var(--accent);
  padding: 0.6rem 0.9rem;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
}
.unit-legend {
  list-style: none;
  margin: 0.4rem 0 0;
  padding: 0;
  display: grid;
  gap: 0.35rem;
  font-size: 0.9rem;
  color: var(--text-soft);
}
.unit-legend li { line-height: 1.4; }
.legend-unit {
  display: inline-block;
  min-width: 3.6em;
  font-weight: 700;
  color: var(--primary);
}
.converter-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.8rem;
  align-items: flex-end;
}
.converter-field { display: flex; flex-direction: column; gap: 0.3rem; flex: 1; min-width: 130px; }
.converter-field label { font-size: 0.85rem; font-weight: 600; color: var(--text-soft); }
.converter input, .converter select {
  font-family: inherit;
  font-size: 1rem;
  padding: 0.6rem 0.7rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
}
.converter input:focus, .converter select:focus {
  outline: 2px solid var(--primary);
  outline-offset: 1px;
}
.converter-equals { font-size: 1.5rem; font-weight: 800; color: var(--text-soft); padding-bottom: 0.5rem; }
.converter-result {
  margin-top: 1rem;
  font-size: 1.2rem;
  font-weight: 700;
  background: var(--primary-soft);
  color: var(--text);
  padding: 0.8rem 1rem;
  border-radius: var(--radius-sm);
}
.converter-result strong { color: var(--primary-strong); }

/* ---------------- Bottoni ---------------- */
.btn {
  font-family: inherit;
  font-size: 1rem;
  font-weight: 700;
  padding: 0.7rem 1.3rem;
  border-radius: 999px;
  border: 1px solid transparent;
  cursor: pointer;
  transition: all 0.2s ease;
}
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-strong); transform: translateY(-1px); }
.btn-ghost { background: transparent; color: var(--primary); border-color: var(--border); }
.btn-ghost:hover { background: var(--bg-soft); }
.btn-lg { font-size: 1.1rem; padding: 0.85rem 1.7rem; }
.cta-row { display: flex; gap: 0.8rem; flex-wrap: wrap; margin-top: 1rem; }

/* ---------------- Quiz ---------------- */
.quiz-launcher { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 1.5rem; box-shadow: var(--shadow-sm); }
.quiz-choice { margin-bottom: 1.5rem; }
.chip-row { display: flex; flex-wrap: wrap; gap: 0.5rem; }
.chip {
  font-family: inherit;
  font-size: 0.95rem;
  font-weight: 600;
  padding: 0.55rem 1rem;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: var(--surface-2);
  color: var(--text);
  cursor: pointer;
  transition: all 0.18s ease;
}
.chip:hover { border-color: var(--primary); }
.chip.is-active { background: var(--primary); color: #fff; border-color: var(--primary); }

/* Quiz runner */
.quiz-runner { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 1.5rem; box-shadow: var(--shadow-sm); }
.quiz-topbar { display: flex; align-items: center; justify-content: space-between; gap: 1rem; margin-bottom: 1.2rem; flex-wrap: wrap; }
.quiz-progress { flex: 1; min-width: 180px; }
.quiz-progress span { font-size: 0.85rem; font-weight: 600; color: var(--text-soft); }
.progress-track { height: 8px; background: var(--bg-soft); border-radius: 999px; overflow: hidden; margin-top: 0.3rem; }
.progress-fill { height: 100%; width: 0; background: var(--primary); border-radius: 999px; transition: width 0.3s ease; }
.quiz-score { font-size: 0.95rem; }

.quiz-card { margin-bottom: 1.3rem; }
.quiz-question { font-size: 1.25rem; font-weight: 700; margin: 0 0 1.1rem; }
.quiz-question .q-tag {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--accent);
  background: var(--surface-2);
  padding: 0.2rem 0.6rem;
  border-radius: 999px;
  margin-bottom: 0.6rem;
}

.answer-options { display: flex; flex-direction: column; gap: 0.6rem; }
.answer-btn {
  text-align: left;
  font-family: inherit;
  font-size: 1rem;
  padding: 0.8rem 1rem;
  border-radius: var(--radius-sm);
  border: 1.5px solid var(--border);
  background: var(--surface-2);
  color: var(--text);
  cursor: pointer;
  transition: all 0.15s ease;
}
.answer-btn:hover:not(:disabled) { border-color: var(--primary); transform: translateX(2px); }
.answer-btn:disabled { cursor: default; opacity: 0.95; }
.answer-btn.correct { background: var(--success-soft); border-color: var(--success); color: var(--text); font-weight: 700; }
.answer-btn.wrong { background: var(--error-soft); border-color: var(--error); }

.answer-numeric { display: flex; gap: 0.6rem; flex-wrap: wrap; align-items: center; }
.answer-numeric input {
  font-family: inherit;
  font-size: 1.1rem;
  padding: 0.7rem 0.9rem;
  border-radius: var(--radius-sm);
  border: 1.5px solid var(--border);
  background: var(--surface-2);
  color: var(--text);
  flex: 1;
  min-width: 140px;
}
.answer-numeric input:focus { outline: 2px solid var(--primary); outline-offset: 1px; }
.answer-numeric .unit-label { font-size: 1.15rem; font-weight: 700; color: var(--accent); }
.numeric-hint { margin: 0.6rem 0 0; font-size: 0.85rem; color: var(--text-soft); }

.feedback {
  margin-top: 1.1rem;
  padding: 0.9rem 1.1rem;
  border-radius: var(--radius-sm);
  font-size: 0.98rem;
  animation: fadeIn 0.3s ease;
}
.feedback.good { background: var(--success-soft); border: 1px solid var(--success); }
.feedback.bad { background: var(--error-soft); border: 1px solid var(--error); }
.feedback-head { font-weight: 800; margin: 0 0 0.3rem; }
.feedback.good .feedback-head { color: var(--success); }
.feedback.bad .feedback-head { color: var(--error); }
.feedback-body { margin: 0; color: var(--text); }

.quiz-actions { display: flex; justify-content: space-between; gap: 0.8rem; }

/* Riepilogo */
.quiz-summary { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 2rem 1.5rem; text-align: center; box-shadow: var(--shadow-sm); }
.summary-emoji { font-size: 3.5rem; }
.summary-score { font-size: 2.2rem; font-weight: 800; color: var(--primary); margin: 0.3rem 0; }
.summary-msg { font-size: 1.1rem; color: var(--text-soft); margin-bottom: 1.3rem; }
.summary-actions { display: flex; gap: 0.8rem; justify-content: center; flex-wrap: wrap; }
.summary-record {
  font-size: 1rem;
  margin: 0 0 1.2rem;
  padding: 0.6rem 1rem;
  border-radius: var(--radius-sm);
  background: var(--surface-2);
  display: inline-block;
}
.summary-record.new {
  background: var(--success-soft);
  border: 1px solid var(--success);
  font-weight: 700;
}

/* Record nella schermata iniziale */
.record-info {
  margin: 0 0 1rem;
  font-size: 0.95rem;
  color: var(--text-soft);
  background: var(--surface-2);
  padding: 0.6rem 0.9rem;
  border-radius: var(--radius-sm);
  display: inline-block;
}

/* Riepilogo domande sbagliate */
.review-perfect {
  margin: 1.5rem 0 0;
  font-weight: 700;
  color: var(--success);
}
.review-block { margin-top: 1.8rem; text-align: left; }
.review-title { font-size: 1.1rem; margin: 0 0 0.9rem; text-align: center; }
.review-list { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: 0.9rem; }
.review-item {
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-left: 3px solid var(--error);
  border-radius: var(--radius-sm);
  padding: 0.9rem 1.1rem;
}
.review-q { margin: 0 0 0.5rem; font-weight: 600; }
.review-q .q-tag { margin-right: 0.4rem; }
.review-your { margin: 0 0 0.5rem; font-size: 0.95rem; color: var(--text-soft); }
.review-your .wrong-text { color: var(--error); font-weight: 700; }
.review-why { margin: 0; font-size: 0.95rem; }

/* ---------------- Footer ---------------- */
.site-footer {
  text-align: center;
  padding: 1.5rem 1rem;
  color: var(--text-soft);
  font-size: 0.88rem;
  border-top: 1px solid var(--border);
}

/* ---------------- Avvio quiz / esercizi ---------------- */
.quiz-start { text-align: center; padding: 1rem 0.5rem; }
.quiz-start h2 { margin-bottom: 0.6rem; }
.quiz-start-desc { color: var(--text-soft); max-width: 55ch; margin: 0 auto 1.2rem; }

/* ---------------- Esercizi guidati ---------------- */
.guided-tools { display: flex; gap: 0.6rem; flex-wrap: wrap; margin-bottom: 0.6rem; }
.btn-sm { font-size: 0.88rem; padding: 0.45rem 0.9rem; }
.guided-reveal {
  background: var(--surface-2);
  border-left: 3px solid var(--accent);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  padding: 0.7rem 1rem;
  margin: 0 0 0.8rem;
  font-size: 0.95rem;
  animation: fadeIn 0.25s ease;
}

/* ---------------- Stati risposta aggiuntivi ---------------- */
.answer-btn.chosen { background: var(--primary-soft); border-color: var(--primary); font-weight: 700; }
.review-item.ok { border-left-color: var(--success); }
.review-your .ok-text { color: var(--success); font-weight: 700; }

.quiz-summary-inner { text-align: center; animation: fadeIn 0.3s ease; }
.quiz-summary-inner .review-block { text-align: left; }

/* ---------------- Responsive ---------------- */
@media (max-width: 640px) {
  .main-nav { order: 3; width: 100%; justify-content: flex-start; overflow-x: auto; }
  .measure-number { font-size: 2.2rem; }
  .compare-grid { grid-template-columns: 1fr; }
  .subnav { flex-wrap: nowrap; overflow-x: auto; border-radius: var(--radius-sm); }
  .subnav-btn { flex: 0 0 auto; }
}

@media (prefers-reduced-motion: reduce) {
  * { animation: none !important; transition: none !important; scroll-behavior: auto !important; }
}