Friendliness through the typeface: Combo.

This may come in handy:

This is My very recent discovery: thanks to HTC - Android-oriented - themes. HTC enables users not only to choose between various compositions, but to create their own from several parts, like fonts.

This way some time ago I've encountered the Combo font - which I find nice and friendly looking, probably thanks to its rounded style. Moreover, it sometimes resembles the "M" in "McDonald's" logotype - which is also nice association :) .

Official description tells Us one more interesting thing: the font's structure is "based on the elliptical arcs and strokes of a flat-tipped marker pen" (nice to know - another thing I find appealing) - and is recommended for "use in advertisements, headlines and short texts" (although I use it almost everywhere throughout Android and it still adds that friendliness to the UI).

Nevertheless - it is almost a real treasure among other typefaces I like most: Lato and Roboto: Combo is featured in more than 10,000 websites, while Lato in more than 7,900,000 - and Roboto in more than 20,000,000 (as we may read on Google Fonts on October 15, 2018).

Check it out on Google Fonts: https://fonts.google.com/specimen/Combo.