.cartes-avis {
  clip-path: polygon(
    0 0, 100% 0,
    100% calc(100% - 80px),
    calc(100% - 80px) 100%,
    0 100%
  ) !important;
  background:
    linear-gradient(to bottom right, transparent calc(50% - 1px), #ffffff calc(50% - 1px), #ffffff calc(50% + 1px), transparent calc(50% + 1px)) bottom right / 80px 80px no-repeat,
    linear-gradient(#ffffff, #ffffff) left bottom / calc(100% - 80px) 1px no-repeat,
    linear-gradient(#ffffff, #ffffff) top / 100% 1px no-repeat,
    linear-gradient(#ffffff, #ffffff) left / 1px 100% no-repeat,
    linear-gradient(#ffffff, #ffffff) top right / 1px calc(100% - 80px) no-repeat,
    linear-gradient(to bottom, transparent, #3a3a3a) !important;
}