SASS

Why aren't you using placeholders instead of mixins to be more DRY principle compliant?

To avoid the use of !important keyword there is a logical precedence: items' rules are more important then containers' rules and flexbox containers' rules are more important then nested flexbox containers' rules. Lot of selector used have equal weight so it's essential to insert the lower ones - lower in the previous explained logical hierarchy - first in the CSS file. If two groups of selectors, belonging to different levels of the logical hierarchy, have same rules, using placeholders would have meant getting those selectors grouped together.

I want to compile only partially your framework!

Okey, you have to modify only sass/strawberry.sass. But to avoid the use of !important keyword there is a logical precedence: items' rules are more important then containers' rules and flexbox containers' rules are more important then nested flexbox containers' rules. Lot of selector used have equal weight so it's essential to insert the lower ones - lower in the previous explained logical hierarchy - first in the CSS file. Respect this rule while editing the previous mentioned file.

I want to change breakpoints!

Okey, you have to modify only sass/data/_breakpoints.sass.