Default base theme: Dawn 15.2.0
Current customized and optimized theme: Xtrm 

Typography:

Harmonia Sans
Use regular weight (don't overuse bold weight).

Sizes and line-heights:

Heading 1
second line

Heading 2
second line

Heading 3
second line

Heading 4
second line

Heading 4
second line

Heading 4
second line

Spacing:

Use defaults from main page

Section padding:

Min. 24px vertical (prefer over 40px).
Min. 16px horizontal.

Space between elements:

Keep elements breathing!

0 if element has min. 24px padding.
min. 24 px if element has no padding.

Use existing styles.