The art of UI and its more mysterious cousin, UX has made leaps and bounds in development and maturity in the last few years. Most designers will agree with the advent of iOS and Material Design the landscape has vastly improved and become standardized in its approach to bring a sleeker, intuitive and human experience to how we interact with the digital world.
In fact, UI/UX plays such a strong role in our modern world, that the wrong transition or icon could give the wrong impression to the user and thereby destroy the message or end goal you want them to achieve. Good UI and UX people; be it designers or developers, understand that good interfaces are understood by the user inherently, as opposed to be wanted to be understood.
I have amassed a group of inspirational transitions, swipes, toggles and fluid interaction from a variety of sources. All props to the respective designer or UI engineer for these excellent interface interactions.