ammarkhanFront End Web Development Techdegree Student 21,029 Points
My answer is the same but doesn't work.
Here is my workspace snapshot https://w.trhou.se/oafqay8h0z and I can see my code is right how Guil did it but it doesn't run.
Bryan Land7,986 Points
It seems to work just fine, but you only set a transition duration to .1 second, which will not be noticeable to the naked eye. Biology sure is good on frames per second, but there are limits haha!!