html, body {
  margin: 0;
  padding: 0;
  width: 100%;
  height: 100%;
}

body {
  position: relative;
  background-color: black;
  overflow: hidden;
}

/* ===== IMAGEN DE FONDO ===== */
#fondo {
  position: absolute;
  top: 0;
  left: 0;

  width: 100vw;
  height: 100vh;

  background-image: url("img/seccion1.jpg"); /* imagen única */
  background-size: contain;        /* NO se corta */
  background-repeat: no-repeat;
  background-position: center;
  background-color: black;

  z-index: 1;
}

/* ===== BOTONES (MODO EDICIÓN) ===== */
.boton {
  position: absolute;
  z-index: 9999;

  display: block;
  cursor: pointer;

  background-color: transparent;
border: none;

}

/* ===== POSICIONES DE LOS 7 BOTONES ===== */
/* EDITA libremente top / left / width / height */

.b1 { top: 10%; left: 13%; width: 370px; height: 80px; }
.b2 { top: 35%; left: 23%; width: 420px; height: 75px; }
.b3 { top: 48%; left: 60%; width: 345px; height: 80px; }

.b4 { top: 58%; left: 10%; width: 225px; height: 90px; }
.b5 { top: 12%; left: 57%; width: 390px; height: 90px; }
.b6 { top: 77%; left: 70%; width: 300px; height: 90px; }

.b7 { top: 80%; left: 30%; width: 390px; height: 100px; }