soapbox/app/styles/components/still-image.scss

.still-image {
  position: relative;
  overflow: hidden;

  img,
  canvas {
    width: 100%;
    height: 100%;
    display: block;
    object-fit: cover;
    font-family: inherit;
  }

  &--play-on-hover {
    img {
      position: absolute;
      visibility: hidden;
    }

    &:hover img {
      visibility: visible;
    }

    &:hover canvas {
      visibility: hidden;
    }
  }
}