From the Store description:
With Today's Trends, take a quick look at the trends of the day live from your favorite social networking & news web sites.
- Display trends in your country (you can change the default country, town in the settings tab) in real time with regular updates.
- Font and color of the subject change shape depending on the volume of tweets and searched subjects.
- Uses tiles & dynamic notification system for having a quick look to the the latest trends and be notified in case of major events.
- Supports trends topics / hashtags from Twitter, Google, YouTube and Reddit.
Here's Topicstack UWP in action on my Lumia 950:
The initial view in landscape mode, with both topics and hashtags represented - what's hot right now?
On the hamburger menu are also a couple of trend charts, of which more below...
Swiping over on the main lists brings you to general news, YouTube and Reddit, again all sorted according to how popular each item or story is....
Everything can be focussed by country and even town (if required), plus there's a choice of dark and light themes...
One of the Twitter trend charts, showing the relative popularity of each (in this case the death of Hugh Hefner)...
...and the same for Google, I've popped up the '...' menu too, to show that you can refresh the data at any point, to make sure that the trends are bang up to date.
In every case, tapping on any of the trends or topics brings up the appropriate (mobile) web site for more information. Which works, though it would be nice if the likes of Twitter or Tweetium could be specified for Twitter topics and perhaps myTube! for YouTube videos. In other words, the ability to specify custom applications to handle each tapped topic.
A great idea that's currently only 90% realised under Windows 10 Mobile, but still worth grabbing. You can download Topicstack UWP in the Store here.