The first time "fade in" is clicked, a blue rectangle should smoothly fade from white to blue over the course of three seconds.
When "fade out" is clicked, the blue rectangle should smoothly fade from blue to white over the course of three seconds.
When "fade in" is clicked the second time, the blue rectangle should smoothly fade from white to blue over the course of three seconds, and then directly fade out from blue to white over the course of three seconds.
The rendered picture matches the reference image, (except
for possible variations in the labeling text (per CSS2 rules))
after activating the link on the fade-in button the first time
and waiting three seconds for the animation to complete. The picture
should remain looking the same way indefinitely, until another
link is activated.