Will the app cause any changes to my store theme?

The Video Background app does not need to modify any of your templates to run nicely in your store.

We are using the App Embed Block system from Shopify (see https://shopify.dev/docs/apps/online-store/theme-app-extensions/extensions-framework#app-embed-blocks for further explanation).

It handles the injection of our app on your theme, without interfering with or manipulating any file in your store.