There might be a pure CSS way to do it, but I can't think of an easy one right now.
A couple other things, in case you didn't know:
- There's nothing about 'transition' tags in that link that I can see, it's just talking about how to use tags to control CSS.
- That link is for Twine 1.4, and is outdated even for recent versions of Twine 1.4. Also, Story Formats all work differently, and Twine 1.4 didn't have the Snowman format at all.