In modern CSS3, one major evolution was the ability to write behaviors for transitions and animations, something front end developers were asking for over many years. Working directly in HTML and CSS, without the use of JavaScript or Flash, finally made this wish come true. From my own experience, being able to design smooth interactions this way changed how I think about motion on the web and how users feel those changes.

With CSS3 transitions, there is real potential to alter the appearance and behavior of an element whenever a state change occurs, such as hovered, focused, active, or targeted. Animations allow an element to be altered using multiple keyframes, while transitions provide movement from one state to another. In practice, I often set different points at different keyframes, making motion feel natural and intentional rather than sudden.