I got most of the way. I needed MDN for checking the usage of:
- css transition syntax
The hard parts were off-by-1 errors and order of operations errors e.g. why does pressing the next button advance the slideshow 2 slides? Because the function that runs on an interval to advance the slideshow automatically already updated the slide index, but the new slide wasn’t displaying yet.
CodePen occasionally didn’t refresh when I expected it to, leaving some errors in the console for longer than I expected.