my-images/app/assets/stylesheets/images/index.scss

.images {
  display: grid;
  grid-gap: 0.75rem;
  grid-template-columns: repeat(2, 1fr);
  justify-content: space-between;
  list-style: none;
  margin-bottom: 0;
  margin-top: 0;
  padding-left: 0;

  li {
    margin-bottom: 1em;
  }

  img {
    background-color: white;
    max-width: calc(100% - 0.5rem);
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.8);
    border-radius: 2px;
    padding: 0.25rem;
  }

  &__upload {
    aspect-ratio: 1 / 1;

    &-form {
      height: 100%;
    }

    &-label {
      align-items: center;
      border-radius: 2px;
      outline: 1px dashed white;
      display: flex;
      flex-direction: column;
      height: 100%;
      justify-content: center;
      opacity: 0.4;
      width: 100%;
      cursor: pointer;
    }

    &-input {
      display: none;
    }
  }
}

@media (min-width: 380px) {
  ul.images { grid-template-columns: repeat(3, 1fr); }
}

@media (min-width: 590px) {
  ul.images { grid-template-columns: repeat(4, 1fr); }
}

@media (min-width: 820px) {
  ul.images { grid-template-columns: repeat(5, 1fr); }
}

@media (min-width: 1000px) {
  ul.images { grid-template-columns: repeat(6, 1fr); }
}