I found DuckDuckGo's bangs fascinating, but was disappointed by how little search engines inherit that feature. And on top of it, DuckDuckGo has the "!" bang that jumps to the first search result but other search engines offering bangs like Brave Search, searx, You.com don't seem to have that. I also thought that the "!" bang could be extended with the ability to jump to the first search result of a specific site, so I added the "!!" bangs in my extension that allow you to do just that (e.g. typing "!!mdn flatMap" will bring up the MDN page for flatMap). I also added a bunch of extra features like the ability to add custom bangs, ability to search in a search engine with the "site:" parameter using "!@r" (r for Reddit), or "!ddg@r" (specify any other bang as the search engine to use), and the ability to chain multiple bangs together with ";" to open them up in different tabs; it also allows you to use multiple "site:" parameters combined with the OR ("|") operator with "," (e.g. "!@r,yt"). Feel free to mix and match! Also, for those who use it, it supports sync. There's also an option to import/export any settings including custom bangs. I've also added custom handling to fix a few bangs which are usually broken such as "!archived" and "!imgops" (They require unescaped URL as part of the path. However, DDG and other search engines always escape the URL. Banger only escapes the URL if it's part of an URL parameter).

I've been working on it for around 2 months now, and I'm pretty satisfied with the result so far. Let me know if you have any comments/feature suggestions/bug reports/anything else!