main.css

html{
        height: 100%;
        background: linear-gradient(to top right, cyan, pink 60%) fixed;
    }

body{
        margin: 0;
        /* height: 100%; */
        background-repeat: no-repeat;
        background-attachment: fixed;
        /* overflow: hidden; */
    }

#timetableA, #timetableB {
  border-radius: 10px;
  border-style: hidden; /*to remove outer boarders*/
  overflow: hidden; /*remove overflow (pointy edge) from last table entry*/
  height: 100%;
}

#timetableA td, #timetableB td {
  border: 1px solid black;
}

#timetable th{
  height: 5%;
}

.lesson{
    background: rgb(90, 209, 90);
}

/*vertically align text of td with class "rowInfo"*/
.rowInfo{
  height: 100px;
  line-height: 100px;
  text-align: center;
}

/*align "buttons" to the right*/
.buttons{
  float: right;
}

#checkboxtable th:first-child{
  border-left: 1px solid #DBDBDB;
}
#checkboxtable th:last-child{
  border-right: 1px solid #DBDBDB;
}

#checkboxtable th{
  color: white;
  background-color: #3488CE;
}
#checkboxtable td{
  border-left: 1px solid #DBDBDB;
  border-right: 1px solid #DBDBDB;
}
#checkboxtable tr:last-child td{
  border-bottom: 1px solid #DBDBDB;
}

#checkboxtable tr td{
  border-bottom: 1px solid #DBDBDB;
}

/* #emptyField{
    background: rgb(55, 81, 93);
} */

#loading{
    margin-left: auto;
    margin-right: auto;

    position: relative;
    width: 100%;
    height: 100%;
    /* background: linear-gradient(to top right, cyan, pink 60%); */
    background: #42BCCC;
    top: 0;
    left: 0;
    z-index: 99;
}

/*Pure CSS Loader*/
.lds-default {
    /*center loader*/
    display: inline-block;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 80px;
    height: 80px;
  }
.lds-default div {
    position: absolute;
    width: 6px;
    height: 6px;
    background: #fff;
    border-radius: 50%;
    animation: lds-default 1.2s linear infinite;
  }
.lds-default div:nth-child(1) {
    animation-delay: 0s;
    top: 37px;
    left: 66px;
  }
.lds-default div:nth-child(2) {
    animation-delay: -0.1s;
    top: 22px;
    left: 62px;
  }
.lds-default div:nth-child(3) {
    animation-delay: -0.2s;
    top: 11px;
    left: 52px;
  }
.lds-default div:nth-child(4) {
    animation-delay: -0.3s;
    top: 7px;
    left: 37px;
  }
.lds-default div:nth-child(5) {
    animation-delay: -0.4s;
    top: 11px;
    left: 22px;
  }
.lds-default div:nth-child(6) {
    animation-delay: -0.5s;
    top: 22px;
    left: 11px;
  }
.lds-default div:nth-child(7) {
    animation-delay: -0.6s;
    top: 37px;
    left: 7px;
  }
.lds-default div:nth-child(8) {
    animation-delay: -0.7s;
    top: 52px;
    left: 11px;
  }
.lds-default div:nth-child(9) {
    animation-delay: -0.8s;
    top: 62px;
    left: 22px;
  }
.lds-default div:nth-child(10) {
    animation-delay: -0.9s;
    top: 66px;
    left: 37px;
  }
.lds-default div:nth-child(11) {
    animation-delay: -1s;
    top: 62px;
    left: 52px;
  }
.lds-default div:nth-child(12) {
    animation-delay: -1.1s;
    top: 52px;
    left: 62px;
  }
@keyframes lds-default {
  0%, 20%, 80%, 100% {
    transform: scale(1);
  }
  50% {
    transform: scale(1.5);
  }
}