How to find out if an App in the Mac App Store is 64 bit I want to buy a game in the Mac App Store. 

How can I check before buying if the game/app is 64 bit or not?

I would like to know because 10.13.4 is displaying warnings about 32 bit apps/games. And probably 10.14 doesn't run 32 bit apps/games at all.
If the app in question was updated after June 2015, or if it was released after February 2015 the app it's 64 bit.

Why:

Apple stopped accepting new apps without 64 bit support in february 2015 and stopped accepting updates to existing apps without 64 bit support in June 2015.