Got new idea about "minus" on the left side of the text:
It would be wonderfull if we would be able to hide(with the help of "minus") different parts of the code
For example:
line1
/* + */
line2
line3
/* - */
/* + */ means that "minus" on the left side would appear
/* - */ means that all code between /* + */ and it would be hide
so, user would be able to hide 2-nd and 3-rd lines of this code