excalidraw/excalidraw-app/components/AppSidebar.scss

.excalidraw {
  .app-sidebar-promo-container {
    padding: 0.75rem;
    display: flex;
    flex-direction: column;
    text-align: center;
    gap: 1rem;
    flex: 1 1 auto;
  }

  .app-sidebar-promo-image {
    margin: 1rem 0;

    height: 16.25rem;
    background-size: contain;
    background-position: center;
    background-repeat: no-repeat;

    background-image: radial-gradient(
        circle,
        transparent 60%,
        var(--sidebar-bg-color) 100%
      ),
      var(--image-source);

    display: flex;
  }

  .app-sidebar-promo-text {
    padding: 0 2rem;
  }

  .link-button {
    margin: 0 auto;
  }
}