refactor(stylesheet): make everything more consistent

[Gitleptune]

changes:

• spaces after all colons (:)
• replace white & black with #fff and #000 (shorter)
• remove empty lines where they aren't needed
• add more comments; have comments always start with a capital letter

[ArthurSonzogni]

Thanks!

I like the changes:

• spaces after all colons (: )
• add more comments; have comments always start with a capital letter

but I would prefer not to have:

• remove empty lines where they aren't needed
• replace white & black with #fff and #000 (shorter)

[ArthurSonzogni]

Thanks!