`"No Distractions" for Twitter` works in a very simple manner: it injects a style sheet and content script to twitter.com which lets the user hide potentially distracting elements and save their preferences in local storage.
On Mac, after you have installed the app, the extension will appear in Safari > Preferences... > Extensions . Here, you can turn the extension off and on.
On iPhone, after you have installed the app, the extension will appear if you go to Safari and tap 'Aa' next to the address bar. Turn the extension on by tapping 'Manage extension', then tap the extension itself to allow it to access twitter.com.
If you have any problems, contact me at firstname.lastname@example.org or create a GitHub issue on the repository github.com/ulyngs/open-source-no-distractions-for-twitter/.