* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: 'Segoe UI', sans-serif;
  background-color: #0f172a;
  color: #e2e8f0;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 4vh 0;
  min-height: 100vh;
}

/* Título */
h2 {
  font-size: 2rem;
  background: #1e293b;
  padding: 12px 24px;
  border-radius: 10px;
  margin-bottom: 2rem;
  text-align: center;
  box-shadow: 0 4px 10px rgba(0, 0, 0, 0.4);
}

/* Tablero Sudoku */
#initialBoard {
  display: flex;
  flex-direction: column;
  gap: 4px;
  width: 70%;
  max-width: 500px;
  padding: 12px;
  background-color: #1e1e2f;
  border-radius: 12px;
  box-shadow: 0 0 18px rgba(0, 0, 0, 0.6);
  margin-bottom: 2rem;
  overflow: hidden;
}

#initialBoard .row {
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  gap: 4px;
  width: 100%;
}

@media (max-width: 768px) {
  #initialBoard {
    width: 90%;
  }
}

#initialBoard input {
  width: 100%;
  aspect-ratio: 1 / 1;
  font-size: 1.2rem;
  text-align: center;
  border: 1px solid #334155;
  background: #2c2f48;
  color: #fff;
  border-radius: 6px;
  outline: none;
  transition: border 0.2s, background 0.2s;
}

#initialBoard input:focus {
  border: 2px solid #60a5fa;
  background-color: #1e293b;
}

/* Botón */
button {
  background: #3b82f6;
  color: white;
  padding: 12px 28px;
  font-size: 1rem;
  border: none;
  border-radius: 10px;
  cursor: pointer;
  transition: background 0.2s ease, transform 0.2s ease;
  box-shadow: 0 4px 10px rgba(59, 130, 246, 0.4);
  margin-bottom: 2rem;
}

button:hover {
  background: #2563eb;
  transform: scale(1.03);
}

/* Resultados */
#answerBoard {
  background: #1e293b;
  padding: 20px;
  border-radius: 12px;
  width: 70%;
  max-width: 500px;
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.5);
  margin-bottom: 2rem;
  overflow-x: auto;
}

@media (max-width: 768px) {
  #answerBoard {
    width: 90%;
  }
}

#answerBoard h2 {
  font-size: 1.3rem;
  color: #60a5fa;
  text-align: center;
  margin-bottom: 10px;
}

#answerBoard p {
  font-family: monospace;
  font-size: 1.1rem;
  text-align: center;
  margin: 6px 0;
  letter-spacing: 0.4rem;
  white-space: nowrap;
  overflow-x: auto;
}

/* Footer */
footer {
  background: #1e293b;
  color: #94a3b8;
  padding: 16px 20px;
  border-radius: 12px;
  text-align: center;
  font-size: 0.9rem;
  max-width: 90%;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.4);
  margin-top: auto;
}

footer a {
  color: #3b82f6;
  text-decoration: none;
}

footer a:hover {
  text-decoration: underline;
}