.container-acc {
  display: flex;
  width: 100%;
  padding: 1% 0% 0 0%;
  box-sizing: border-box;
  height: 100vh;
}

.box-acc {
  flex: 1;
  overflow: hidden;
  transition: 2.5s;
  margin: 0 1% 0 0;
/*  box-shadow: 0 20px 30px rgba(0,0,0,.1);	*/
  line-height: 0;
}

.box-acc > img {
  width: 200%;
  height: calc(100% - 0vh);
/*  height: calc(100% - 10vh);   /* nur einsetzen, wenn <span> aktiv ist */
  object-fit: cover; 
  transition: 0.5s;
}

/*
.box-acc > span {
  font-size: 3.8vh;
  display: block;
  text-align: center;
  height:  10vh;
  line-height: 2.6;
}
*/

.box-acc:hover { flex: 1 1 90%; }	/* % zeigt den aktiven ACC */
.box-acc:hover > img {
  width: 100%;
  height: 100%;
}