#picQuizTbl {
  display: grid;
  grid-template-columns: repeat(8, minmax(0, 1fr));
  grid-template-rows: repeat(6, minmax(0, 1fr));
  background-repeat: no-repeat;
  background-position: top left;
  background-size: 100% 100%;
  margin-left: auto;
  margin-right: auto;
  width: 900px;
  user-select: none;
}

#picQuizTbl > div {
  min-width: 0;
  min-height: 0;
}

.picQuizTd {
  position: relative;
  box-sizing: border-box;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
  background-color: cornflowerblue;
  color: #fff;
  font-size: 22px;
  line-height: 1;
  text-align: center;
  cursor: pointer;
  padding: 0;
}

/* Lines are painted on top of the square so removing one never changes its size. */
.picQuizTd::after {
  content: "";
  position: absolute;
  inset: 0;
  pointer-events: none;
  border-right: 1px solid #fff;
  border-bottom: 1px solid #fff;
}

.picQuizTd:nth-child(8n + 1)::after {
  border-left: 1px solid #fff;
}

.picQuizTd:nth-child(-n + 8)::after {
  border-top: 1px solid #fff;
}