ACOS Shell

The ACOS Shell is a  command-line interpreter or  shell that provides a traditional  user interface for the ACOS . Users direct the operation of the  computer by entering commands as text for a  command line interpreter to execute, or by creating text scripts of one or more such commands.

S4 Behaviour
As an S4 app, Shell reacts to user input either by activating a widget (left mouse button click) or by summoning a Card (right click).

Left Mouse Click
When left clicked, an overlay element in the form of a dark grey or black panel rolls down from the top of the screen up to about 60% of its height. The panel contains an interactive shell instance that doesn't exit when the panel is closed. While the animation of the panel is active, the Shell S4 button moves to the left and a bar of colour replaces the S4 and shows the title of the shell instance. The Menu button is still visible, however, and clicking it will still trigger the Menu as usual, however the Shell panel will be hidden by doing so.

Right Mouse Click
Clicking the Shell S4 button with RMB will open a Card (floating by default) of a shell instance.

Features
The ACOS Shell will probably be similar to Bash, a popular Unix shell. It might be based off ClamShell.