From NinjaKiwi blog:
>Ads are almost entirely rewarded - you watch them if you want to and if the value they offer (bonus shots, shuffling the shots in your inventory, one more chance if the Bloons have leaked, bonus rewards) makes sense to you. Full disclosure there are interstitial ads in the game, but only if you have not purchased IAP and if you have not done any rewarded ads over several levels.
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