https://www.cnet.com/news/google-play-instant-will-let-you-test-out-android-games-before-downloading-them-gdc/

You'll now be able to try out Android games before buying them.

Google on Monday rolled out Google Play Instant in its Google Play store. You can tap on one of the games listed and play it without having to buy or download it first. Some of the initial games include Clash Royale, Words with Friends 2 and Final Fantasy XV.