/* =========================================================
   DESIGN TOKENS (light/dark via data-theme)
   Palette, ombre e variabili di base per garantire coerenza
   visiva e facilità di manutenzione tra i temi.
   ========================================================= */
:root {
  --bg: #f6f7f9;
  --text: #1f2937;
  --muted: #6b7280;
  --card: rgba(255, 255, 255, 0.85);
  --border: #e5e7eb;
  --ring: #1f6feb;
  --btn-bg: #1f6feb;
  --btn-bg-hover: #155edc;
  --shadow: 0 10px 30px rgba(4, 20, 40, 0.12);
  --glass-blur: saturate(180%) blur(8px);
  --chip-bg: #eef2ff;
  --chip-text: #3730a3;
}

/* Tema scuro: override cromatici attivati da body[data-theme="dark"] */
body[data-theme="dark"] {
  --bg: #0d1117;
  --text: #e5e7eb;
  --muted: #94a3b8;
  --card: rgba(22, 27, 34, 0.7);
  --border: #1f2937;
  --ring: #60a5fa;
  --btn-bg: #2563eb;
  --btn-bg-hover: #1d4ed8;
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.5);
  --chip-bg: #111827;
  --chip-text: #c7d2fe;
}

/* =========================================================
   BASE / RESET
   Normalizza il box model, imposta tipografia e sfondo.
   Gradiente leggero per profondità senza penalizzare leggibilità.
   ========================================================= */
* {
  box-sizing: border-box;
}
html,
body {
  height: 100%;
}
body {
  margin: 0;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  color: var(--text);
  background: radial-gradient(
      1200px 600px at 10% -10%,
      rgba(99, 102, 241, 0.18),
      transparent 60%
    ),
    radial-gradient(
      800px 500px at 110% 10%,
      rgba(56, 189, 248, 0.18),
      transparent 60%
    ),
    var(--bg);
  transition: background-color 0.25s ease, color 0.25s ease; /* transizioni morbide tra temi */
}

/* =========================================================
   ICONA CAMBIO TEMA
   Interattiva ma non “button-like”: nessun bordo/sfondo/ombra,
   restando accessibile e con feedback hover discreto.
   ========================================================= */
.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: 0.75;
}
.theme-icon:hover {
  opacity: 1;
  transform: scale(1.1);
}
.theme-icon:focus {
  outline: none; /* focus gestito a livello app; qui evitiamo alone predefinito */
}

/* =========================================================
   LAYOUT
   Contenuto centrato verticalmente/orizzontalmente con ritmo
   verticale uniforme tra le sezioni principali.
   ========================================================= */
.container {
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center; /* centratura verticale */
  padding: 2rem 1rem; /* spazio contenuto per ridurre “vuoti” */
  gap: 1rem; /* spaziatura coerente tra header/card/footer */
}

.header {
  text-align: center;
  margin-bottom: 1rem;
}
.title {
  margin: 0;
  font-size: clamp(1.6rem, 2.8vw, 2rem);
  letter-spacing: 0.2px;
}

/* =========================================================
   BANNER INFORMATIVO
   Evidenzia la definizione con un accento cromatico coerente.
   Testo centrato per leggibilità, ombra e blur per effetto “glass”.
   ========================================================= */
.banner {
  background: color-mix(in srgb, var(--ring) 12%, transparent);
  border: 1px solid color-mix(in srgb, var(--ring) 25%, transparent);
  border-radius: 12px;
  padding: 0.8rem 1.1rem;
  margin: 0.5rem auto 0.8rem; /* margine ridotto per avvicinare all’input */
  width: min(720px, 92vw);
  box-shadow: var(--shadow);
  backdrop-filter: var(--glass-blur);
  color: var(--text);
  font-size: 0.95rem;
  line-height: 1.45;
  text-align: center;
}
.banner strong {
  color: var(--ring);
}
.banner em {
  font-style: normal;
  font-weight: 600;
  color: var(--ring);
}

/* Nota informativa sotto la card: tono secondario e centrata */
.info {
  text-align: center;
  font-size: 0.9rem;
  color: var(--muted);
  margin-top: 0.6rem;
}

/* =========================================================
   CARD
   Pannello principale con effetto vetro, bordo sottile e ombra.
   Padding compresso per equilibrio visivo con il banner.
   ========================================================= */
.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;
  transition: background 0.25s ease, border-color 0.25s ease;
}

/* =========================================================
   CONTROLLI (INPUT + BUTTON)
   Alti contrasti e focus ben visibile. Animazioni sottili per
   non distrarre e garantire buon feedback.
   ========================================================= */
.row {
  display: flex;
  gap: 0.6rem;
  align-items: center;
}

/* Campo di testo: trasparente per integrare la card, focus “ring” coerente */
.input {
  flex: 1;
  padding: 0.8rem 1rem;
  border-radius: 12px;
  border: 1px solid var(--border);
  font-size: 1rem;
  background: transparent;
  color: var(--text);
  transition: border-color 0.2s ease, box-shadow 0.2s ease, background 0.2s ease;
}
.input::placeholder {
  color: color-mix(in srgb, var(--muted) 80%, transparent);
}
.input:focus {
  outline: none;
  border-color: var(--ring);
  box-shadow: 0 0 0 4px color-mix(in srgb, var(--ring) 25%, transparent);
  background: color-mix(in srgb, var(--card) 65%, transparent);
}

/* Pulsante primario: colore brand, hover/active/keyboard states */
.btn {
  padding: 0.8rem 1rem;
  border: 0;
  border-radius: 12px;
  font-weight: 700;
  cursor: pointer;
  background: var(--btn-bg);
  color: white;
  transition: background 0.2s ease, transform 0.06s ease;
}
.btn:hover {
  background: var(--btn-bg-hover);
}
.btn:active {
  transform: translateY(1px);
}
.btn:focus {
  outline: 2px solid var(--ring);
  outline-offset: 2px;
}

/* =========================================================
   RISULTATO
   Spazio minimo per evitare “salti” del layout quando vuoto.
   ========================================================= */
.result {
  margin-top: 1rem;
  font-size: 1.05rem;
  min-height: 1.6em;
  text-align: center;
  transition: color 0.25s ease, transform 0.15s ease;
}

.result.is-palindrome {
  color: #16a34a; /* verde - success */
  font-weight: 600;
}

.result.not-palindrome {
  color: #dc2626; /* rosso - error */
  font-weight: 600;
}

.result strong {
  font-weight: 700;
}

.result.is-palindrome::before {
  content: "✅";
  margin-right: 6px;
}

.result.not-palindrome::before {
  content: "❌";
  margin-right: 6px;
}

/* =========================================================
   ESEMPI RAPIDI (DETAILS)
   Disclosure progressivo, griglia fluida e “chip” cliccabili
   che compilano l’input.
   ========================================================= */
.tips {
  margin-top: 0.75rem;
  border-top: 1px dashed var(--border);
  padding-top: 0.75rem;
}
.tips > summary {
  cursor: pointer;
  color: var(--muted);
  font-size: 0.95rem;
  margin-bottom: 0.5rem;
}
.tips-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
  gap: 0.5rem;
  margin-top: 0.5rem;
}
.chip {
  border: 1px solid var(--border);
  background: var(--chip-bg);
  color: var(--chip-text);
  border-radius: 999px;
  padding: 0.45rem 0.75rem;
  font-size: 0.9rem;
  cursor: pointer;
  transition: transform 0.08s ease, filter 0.2s ease, background 0.2s ease;
}
.chip:hover {
  filter: brightness(0.98);
}
.chip:active {
  transform: translateY(1px);
}
.chip:focus {
  outline: 2px solid var(--ring);
  outline-offset: 2px;
}

/* =========================================================
   FOOTER / BADGE
   Piccolo richiamo informativo in tono neutro, coerente con la card.
   ========================================================= */
.footer {
  margin-top: 1rem;
}
.badge {
  display: inline-block;
  font-size: 0.75rem;
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 0.25rem 0.6rem;
  background: color-mix(in srgb, var(--ring) 12%, transparent);
  backdrop-filter: var(--glass-blur);
}