The Twenty Fifteen Theme

The Twenty Fifteen theme at WordPress Codex

"Twenty Fifteen is the default theme for WordPress in 2015. It is super-clean, content-focused, and designed to bring a little more simplicity to our blogs. Its careful attention to typography, featuring the expertly-designed Noto font set in elegant and harmonious margins, makes it beautiful in multiple languages around the world."

Twenty Fifteen at the WordPress.com Themes Directory

Twenty Fifteen's simple, straightforward typography is readable on a wide variety of screen sizes, and suitable for multiple languages. We designed it using a mobile-first approach, meaning your content takes center-stage, regardless of whether your visitors arrive by smartphone, tablet, laptop, or desktop computer.

Twenty Fifteen at the WordPress.org Themes Directory

and the Twenty Fifteen Support Forum

(NOTE: this is at WordPress.org where you can edit the backend – so some of the solutions do not apply if you are using it at wordpress.com)