My First Andriod Game - Saving Santa

Hi, my husband and I made our first game with Unity and Playmaker and it is now available on Google Play, and in review for iOS App Store. We are pretty excited, but would also like any feedback if anyone has time. Challenging is one word that has come up numerous times in the reviews, so wondering is it too hard? is there enough to it? does it get boring?
I was going for simple, challenging, addictive - a game that is challenging enough so that you want to keep going to beat your/other peoples scores.
Would love to get anyone opinion!
https://play.google.com/store/apps/details?id=com.stevengubbins.savingsanta&hl=en
Thanks,
Jo