You're designing a button that, when clicked, shows a loading spinner. The spinner should rotate continuously. Which properties are crucial for this effect?

To create a loading spinner that rotates continuously, you need to use CSS animations. Key properties for this effect include animation-duration (to control the duration of the animation), animation-timing-function (to specify the timing function for animation), animation-iteration-count (to set it to 'infinite' for continuous rotation), and animation-direction (to make it rotate continuously using 'alternate' or 'normal').