I used the Sketch "Delicious" free UI Kit for a food recipes app. It includes 11 pixel-perfect screens. I just added Proto.io interactions and created a great prototype! This Delicious UI Kit was designed by Robert Anitei Sketch source: https://www.sketchappsources.com/free-source/1765-delicious-ui-kit-sketch-freebie-resource.html

A website template with multilevel dropdown menus and scrolling area.

Music App project Design Credits: https://www.sketchappsources.com/free-source/2847-apple-music-app-sketch-freebie-resource.html

A simple endless runner. You can jump by tapping the screen, hitting the space bar on your keyboard or hitting the up arrow key.