/* =========================================================
   THEME TOKENS (teal/rose) + DARK OVERRIDES
   - Design tokens centralizzati per garantire consistenza visiva.
   - L’uso di color-mix modernizza la gestione delle trasparenze/mescolanze.
   ========================================================= */
:root {
  --bg: #f8fafb;
  --text: #0f172a;
  --muted: #5b647d;

  --card: rgba(255, 255, 255, 0.9);
  --border: #e6e8ef;
  --shadow: 0 14px 36px rgba(16, 24, 40, 0.12);
  --glass-blur: saturate(170%) blur(8px);

  --brand: #0ea5a4;      
  --brand-2: #fb7185;    
  --ring: #7dd3fc;       

  --btn-grad: linear-gradient(135deg, #22d3ee, #fb7185);
  --btn-grad-hover: linear-gradient(135deg, #06b6d4, #f43f5e);

  /* Fondo input leggermente tinto per dare affordance di editabilità */
  --field-bg: color-mix(in srgb, #22d3ee 6%, transparent);
}

/* Modalità scura: override token per contrasto e ombreggiature coerenti */
body[data-theme="dark"] {
  --bg: #0b1020;
  --text: #e6eaf6;
  --muted: #aab0d3;

  --card: rgba(18, 22, 50, 0.78);
  --border: #22264a;
  --shadow: 0 18px 40px rgba(0, 0, 0, 0.55);

  --brand: #2dd4bf;
  --brand-2: #fb7185;
  --ring: #38bdf8;

  --btn-grad: linear-gradient(135deg, #22d3ee, #fb7185);
  --btn-grad-hover: linear-gradient(135deg, #06b6d4, #f43f5e);

  --field-bg: color-mix(in srgb, #0ea5a4 9%, transparent);
}

/* =========================================================
   BASE / RESET
   - Box sizing border-box evita calcoli di layout imprevisti.
   - Altezza 100% su html/body per facilitare centratura verticale.
   ========================================================= */
*,
*::before,
*::after { box-sizing: border-box; }

html, body { height: 100%; }

body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Inter, Roboto, Arial, sans-serif;
  color: var(--text);
  /* Background composito: gradient radiali per profondità, fallback su tinta base. */
  background:
    radial-gradient(1100px 520px at -10% -20%, rgba(34, 211, 238, 0.12), transparent 60%),
    radial-gradient(900px 520px at 120% 0%, rgba(251, 113, 133, 0.10), transparent 60%),
    var(--bg);
  transition: background-color 0.25s ease, color 0.25s ease;
}

/* =========================================================
   THEME TOGGLE
   - Posizionamento fisso in alto a destra.
   - Transizioni sottili per feedback di interazione senza distrazioni.
   ========================================================= */
.theme-icon {
  position: fixed;
  top: 14px;
  right: 18px;
  font-size: 1.4rem;
  line-height: 1;
  cursor: pointer;
  user-select: none;
  color: var(--text);
  background: transparent;
  border: none;
  box-shadow: none;
  padding: 0;
  transition: transform 0.1s ease, opacity 0.2s ease;
  opacity: 0.8;
}
.theme-icon:hover { opacity: 1; transform: scale(1.08); }
.theme-icon:focus { outline: none; }

/* =========================================================
   LAYOUT CENTRATO
   - Flex column per impilare header/card/banner.
   - gap per spaziatura consistente tra sezioni.
   ========================================================= */
.container {
  min-height: 100dvh; 
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 1rem;
  padding: 2rem 1rem;
}

.header { text-align: center; margin: 0; }

.title {
  margin: 0 0 0.25rem 0;
  font-size: clamp(1.7rem, 3.4vw, 2.2rem); 
  letter-spacing: 0.2px;
  /* Effetto testo a gradiente: restituisce una gerarchia visiva elegante */
  background: linear-gradient(90deg, var(--brand), var(--brand-2));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.subtitle { margin: 0; color: var(--muted); font-size: 0.95rem; }

/* =========================================================
   CARD
   - Lieve glassmorphism (backdrop-filter) con ombra per elevazione.
   - width responsiva con max 720px per leggibilità.
   ========================================================= */
.card {
  width: min(720px, 92vw);
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 16px;
  box-shadow: var(--shadow);
  backdrop-filter: var(--glass-blur);
  padding: 1rem 1.25rem;
}

/* =========================================================
   INPUT + BUTTONS (responsive)
   - Grid a 1 colonna su mobile, 3 colonne su desktop.
   - gap coerente con spacing scale.
   ========================================================= */
.row {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.6rem;
}

@media (min-width: 720px) {
  .row {
    grid-template-columns: 1fr auto auto;  
    align-items: stretch;
  }
}

/* Input */
.input {
  padding: 0.9rem 1rem;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: var(--field-bg);
  color: var(--text);
  font-size: 1rem;
  transition: border-color 0.2s ease, box-shadow 0.2s ease, background 0.2s ease;
}
.input::placeholder { color: color-mix(in srgb, var(--muted) 75%, transparent); }
.input:focus {
  outline: none;
  border-color: var(--ring);
  /* Focus ring accessibile e non invasivo */
  box-shadow: 0 0 0 4px color-mix(in srgb, var(--ring) 28%, transparent);
  background: color-mix(in srgb, var(--card) 55%, transparent);
}

/* Bottoni */
.btn {
  padding: 0.9rem 1.1rem;
  border: 0;
  border-radius: 12px;
  font-weight: 800;
  letter-spacing: 0.3px;
  cursor: pointer;
  transition: transform 0.06s ease, filter 0.15s ease, box-shadow 0.15s ease, background 0.2s ease;
}

.btn.primary {
  color: #07161a;
  background: var(--btn-grad);
  box-shadow: 0 8px 22px rgba(2, 132, 199, 0.25);
}
.btn.primary:hover { filter: brightness(1.06); background: var(--btn-grad-hover); }
.btn.primary:active { transform: translateY(1px); }

.btn.ghost {
  color: var(--text);
  background: transparent;
  border: 1px solid var(--border);
}
.btn.ghost:hover { filter: brightness(1.06); }
.btn.ghost:active { transform: translateY(1px); }

.btn:focus { outline: 2px solid var(--ring); outline-offset: 2px; }

/* Mobile: bottoni a larghezza piena per tap target adeguati */
@media (max-width: 719.98px) {
  .btn { width: 100%; }
}

/* =========================================================
   RISULTATO
   - Transizione colore per feedback morbido.
   - classi .ok / .err set by JS per semantica visiva immediata.
   ========================================================= */
.result {
  margin-top: 1rem;
  font-size: 1.05rem;
  min-height: 1.6em; 
  text-align: center;
  transition: color 0.25s ease;
}
.result.ok  { color: #16a34a; font-weight: 700; }
.result.err { color: #dc2626; font-weight: 700; }

/* =========================================================
   BANNER
   - Evidenziazione delle regole supportate con tono informativo.
   ========================================================= */
.banner {
  width: min(720px, 92vw);
  background: color-mix(in srgb, var(--brand) 12%, transparent);
  border: 1px solid color-mix(in srgb, var(--brand) 28%, transparent);
  border-radius: 14px;
  padding: 0.9rem 1.1rem;
  text-align: center;
  box-shadow: var(--shadow);
  backdrop-filter: var(--glass-blur);
  color: var(--text);
  font-size: 0.95rem;
}
.banner em { font-style: normal; font-weight: 700; color: var(--brand-2); }