Use symbols for command names.
Swap order of arguments;

Allow Dummy interface to be used to lower barrier to entry.
Remove commented out code.
From Practicing Ruby - Event Loops Demystified;
https://practicingruby.com/articles/event-loops-demystified
Whitespace and comment changes.
Tidying, understanding...
Remove underscores.
Add Buffer and Line classes.
Restore Compositor.
Misc.