Is Flappy Budgies Offline. Desktop Version safe?

Flappy Budgies Offline fetches network-filtering rules from a remote server on startup and installs them to control browser traffic.

Each time the extension's service worker starts, it contacts example.com/flappybird/ with credentials and downloads JSON-encoded declarativeNetRequest rules, which it immediately applies as session rules. These rules can redirect, block, or modify headers on any browser request. The game itself runs locally, but this background mechanism gives the operator of example.com/flappybird/ ongoing control over what network requests the browser allows.