User interface guidelines
Designing intuitive applications has become a work of art over the years. In the beginning, developers did not consider applications' usability; they only focused on providing the required functionality.
Since the mobile revolution, back in 2007, an app's design has become as important as its purpose. Applications that are easier to use have had more success than others with more features but less user interface appeal.
All major players in the mobile industry started to define their approaches to user interface design by creating guidelines for their devices. Toolbars were initially at the bottom, then at the top, now they're back at the bottom again. There have been many iterations depending on device sizes, screen aspect ratios, and more.
The main guidelines in use today come from Google, Apple, and Microsoft. It doesn't matter the device, there is a guideline for it. The idea is to give app designers and developers cues on...