.btm-loader {
  width: 40px;
  height: 40px;
  position: relative;
  --c:no-repeat linear-gradient(#1897f1 0 0);
  background: 
    var(--c),var(--c),var(--c),
    var(--c),var(--c),var(--c),
    var(--c),var(--c),var(--c);
  background-size: 16px 16px;
  animation: 
    btm-loader-size 1s infinite,
    btm-loader-position 1s infinite;
}

.btm-loader:before {
  content:'';
  position: absolute;
  inset: 0;
}

@keyframes btm-loader-size {
  0%,100% {width:45px;height: 45px}
  35%,65% {width:65px;height: 65px}
}

@keyframes btm-loader-position {
  0%,40%  {background-position: 0 0,0 50%, 0 100%,50% 100%,100% 100%,100% 50%,100% 0,50% 0,  50% 50% }
  60%,100%{background-position: 0 50%, 0 100%,50% 100%,100% 100%,100% 50%,100% 0,50% 0,0 0,  50% 50% }
}