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

/* Fondo general */
body {
  font-family: 'Segoe UI', Arial, sans-serif;
  background: #0f172a;
  color: #e5e7eb;

  display: flex;
  justify-content: center;
  align-items: center;

  height: 100vh;
}

/* Contenedor principal */
.container {
  background: #1e293b;
  padding: 25px;
  border-radius: 12px;
  width: 90%;
  max-width: 400px;
  box-shadow: 0 0 25px rgba(0, 0, 0, 0.4);
  text-align: center;
}

/* Título */
h1 {
  margin-bottom: 5px;
}

/* Subtítulo */
.subtitle {
  font-size: 14px;
  color: #94a3b8;
  margin-bottom: 20px;
}

/* Input */
input {
  width: 100%;
  padding: 12px;
  border-radius: 8px;
  border: none;
  margin-bottom: 15px;
  font-size: 16px;
}

/* Botón */
button {
  width: 100%;
  padding: 12px;
  border: none;
  border-radius: 8px;
  background: #3b82f6;
  color: white;
  font-size: 16px;
  cursor: pointer;
  transition: 0.2s;
}

button:hover {
  background: #2563eb;
}

/* Resultado */
#resultado {
  margin-top: 20px;
}

/* Fórmula matemática */
.math {
  font-size: 22px;
  margin-top: 10px;
}

/* Autor */
.autor {
  margin-top: 25px;
  font-size: 13px;
  color: #94a3b8;
}

/* 📱 Responsive */
@media (max-width: 480px) {
  body {
    padding: 15px;
    align-items: flex-start;
  }

  .container {
    margin-top: 40px;
    padding: 20px;
  }

  h1 {
    font-size: 22px;
  }

  input, button {
    font-size: 16px;
  }
}