This 18 Cool Gradients was designed by Osama Dawood https://www.sketchappsources.com/free-source/3607-gradients-ui-kit-sketch-freebie-resource.html

Form validation using variables and states

Netflix Desktop UI Sketch Resource Design: https://www.sketchappsources.com/free-source/3590-netflix-desktop-ui-sketch-freebie-resource.html

Setting up a calendar event using Proto.io Templates and Variables

Filtering Activity Feed (Templates) by Tags using Container States Filter / container states

A very basic content shelf component commonly used by TV apps such as Hulu, Youtube, HBO etc. This component uses a fixed focus model where the items in the shelf move into place using key press interactions. Note: Must click the canvas to enable key presses, this seems to be a common restriction with most prototyping tools when building key press focus interaction models.

A Sample project used in various official Proto.io tutorial videos. It contains various design patterns commonly found in popular mobile apps.