* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
  background: #f3f5f7;
  color: #222;
}

.contenedor {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px;
}

.tarjeta {
  width: 100%;
  max-width: 560px;
  background: #ffffff;
  border-radius: 16px;
  padding: 32px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.08);
}

h1 {
  margin: 0 0 16px 0;
  font-size: 28px;
}

.descripcion {
  font-size: 15px;
  line-height: 1.5;
  color: #555;
  margin-bottom: 28px;
}

.grupo {
  margin-bottom: 22px;
}

label {
  display: block;
  font-weight: bold;
  margin-bottom: 10px;
}

input[type='file'] {
  width: 100%;
  padding: 14px;
  border: 1px solid #d7dce1;
  border-radius: 10px;
  background: #fafafa;
}

button,
.boton-volver {
  display: inline-block;
  width: 100%;
  border: none;
  border-radius: 10px;
  padding: 14px 18px;
  background: #111827;
  color: #ffffff;
  font-size: 16px;
  cursor: pointer;
  text-align: center;
  text-decoration: none;
}

button:hover,
.boton-volver:hover {
  background: #000000;
}

#mensaje {
  margin-top: 18px;
  font-size: 14px;
}

.error {
  color: #b91c1c;
  font-weight: bold;
}

.resultado {
  padding: 18px;
  border-radius: 10px;
  margin: 24px 0;
}

.correcto {
  background: #ecfdf5;
  border: 1px solid #a7f3d0;
  color: #065f46;
}

.resultado p {
  margin: 8px 0;
}