This app was mentioned in 7 comments, with an average of 1.29 upvotes
For most such games (eg. our games Tyrant Unleashed, Spellstone, etc.), yeah it's just a REST API. I often explain to web devs our app running on a mobile device works just like the client of a single-page web application.
If your looking for games with pve content:
https://play.google.com/store/apps/details?id=com.kongregate.mobile.spellstone.google
https://play.google.com/store/apps/details?id=com.kongregate.mobile.battlehand.google
https://play.google.com/store/apps/details?id=com.runningpillow.ganymede&hl=en
https://play.google.com/store/apps/details?id=com.tinytouchtales.cardcrawl
bit different, but you may like
https://play.google.com/store/apps/details?id=com.RighteousHammerGames.Solitairica