The free 128K Edition
https://play.google.com/store/apps/details?id=com.iterationgames.CastleNode_128k
The Full game
https://play.google.com/store/apps/details?id=com.iterationgames.CastleNode

The free Edition has NO ADS and can be played as much as you like. This version ends the game when you reach the 128k point maximum, more than enough to be sure the game runs well on your device and that it is interesting to play.

The full version is in need of a difficulty ramp up and that will be in the first update.

This is built with ZGameEditor; http://zgameeditor.org
So you are looking at openGL with real-time synthesized sounds.