Right now the price is $1.99. I got it for free because AppsGoneFree keeps track of cool apps - of all types - that become free for a limited time. About 2 weeks ago, they featured Can't Stop about a week after I paid $1.99. Oh well.
On another note, looking at newly published puzzle apps - there is a deluge of clones of Threes! and 2048! There must be at least 100 of these. What's disappointing is that it's harder to find the real gems under the rubble. If you find something good, do send me an email.