How you stop bliss depends on your platform, and how you started it.
The default bliss application runs in the foreground. Stopping bliss is as simple as closing the window.
If, instead, you are running bliss using the optional Start bliss (in background) launcher, this means bliss is running in the background and its user interface is served soley in a Web browser. In this case, there is no usual 'x' icon to close the application. Closing the Web browser does not stop bliss.
In this case, bliss loads an icon into the System Tray at the bottom right of the screen. By right clicking on this icons you should see a 'Quit' option. bliss stops when you press this 'Quit' button.
On all other platforms, bliss runs in the background and its user interface is served via a Web interface. This means there is no usual 'x' icon to close the application.
Instead, in macOS, bliss loads an icon into the menu bar at the top right. By right clicking on these icons you should see a 'Quit' option. bliss stops when you press this 'Quit' button.
On Linux systems it depends whether you are running a user interface with a system tray concept. If so, the bliss icon should appear here in the same way as above. Otherwise, or alternatively, 'kill' bliss with normal process management commands. A ps -ef | grep bliss should give you the PID.
Any other FAQs I forgot or clarifications required? Post your ideas below!