.mainBoxBG::before,
.mainBoxBG::after {
  content: "";
  position: absolute;
  inset: 0;
  background-size: cover;
  opacity: 0;
  transition: background 2s ease;
  z-index: -1;
}

/* Liste des backgrounds pour 10 slides */
.mainBoxBG.bg-1::before { background: #d981aa url(imagesCSS/BG-lesBoulets1.jpg); opacity: 1; }
.mainBoxBG.bg-2::before { background: #91c0e1 url(imagesCSS/BG-lesBoulets1-bleu.jpg); opacity: 1; }
.mainBoxBG.bg-3::before { background: #a7dd93 url(imagesCSS/BG-lesBoulets1-vert.jpg); opacity: 1; }
/*.mainBoxBG.bg-4::before { background-image: url('/images/bg-4.jpg'); opacity: 1; }
.mainBoxBG.bg-5::before { background-image: url('/images/bg-5.jpg'); opacity: 1; }
.mainBoxBG.bg-6::before { background-image: url('/images/bg-6.jpg'); opacity: 1; }
.mainBoxBG.bg-7::before { background-image: url('/images/bg-7.jpg'); opacity: 1; }
.mainBoxBG.bg-8::before { background-image: url('/images/bg-8.jpg'); opacity: 1; }
.mainBoxBG.bg-9::before { background-image: url('/images/bg-9.jpg'); opacity: 1; }
.mainBoxBG.bg-10::before { background-image: url('/images/bg-10.jpg'); opacity: 1; }*/