@keyframes rotate {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

.spinner {
    width: 40px;
    height: 40px;
    border-radius: 100%;
    border: var(--spinner-stroke-size) solid var(--app-background);
    box-sizing: border-box;
}

.spinner::before {
    content: "";
    display: block;
    width: inherit;
    height: inherit;
    border-radius: 100%;
    border-width: var(--spinner-stroke-size);
    border-style: solid;
    border-color: transparent;
    border-top-color: var(--grey);
    animation: rotate 0.8s linear infinite;
    box-sizing: border-box;
    margin: calc(-1 * var(--spinner-stroke-size));
}