There are people who can never pay you (kids whose parents have disabled IAP). There are people who would have been happy to pay you after 20 levels, but got distracted by a new SuperCell game and never came back to your game. You want to monetize every user, even if it's for 1 cent. Or if you don't monetize them, you want them to tell their friends about your app, to improve your app virality.
I understand if you don't want to bombard your users with IAP and ads, but monetization is truly important. It allows your company to survive. Without it, you might have to go get a job someday, and this will prevent us all from enjoying your awesome games.
Also, it's not clear that there are more level packs if you swipe horizontally. Maybe if you add the three little dots (page indicators) at the bottom? Or maybe arrows that you can tap to change the page? I know this all looks ugly, but sometimes you have to be explicit. There are lots of users who need a bit of guidance to navigate your app.
I had a hard time figuring this out too.
Having said that let me give you some numbers which you can correlate to your download figures to come up with an estimate of how much ad revenue you are leaving on the table. Today you can expect your ad revenue to be about 3-10 USD per 1k bootups. Maybe more if you do some ad mediation between networks to increase fill rates[2] but this is a realistic estimate. This is from personal experience using Chartboost and revmob. To achieve a steady 1k daily bootups, you will need about 150 downloads/day. This is a steady state equilibrium I've found true for my apps, it takes into account new user acquisition rate and churn rate (which is surprisingly high, from my stats only about 80% of users will even open you app, and of those 80% only 30% will open it on the next day, after 30 days you can expect about 5% of users to still be using your app).
There's a lot to be said about App Store monetization but take these numbers into account when considering whether to ad ads to your app. Btw all of the above is for full screen interstitial ads shown once on app launch. And honestly most users are ok with tactful ads that don't interfere with the user experience (predictable and consistent positioning out of the way of gameplay--e.g. at app launch or between levels/after you "die"), I can tell you I've never had a bad review because of ads.
I just wanted to give you some advice re. ads as it's something I emotionally struggled with at the beginning, and I'd hate to see a talented team like yours not get the results you deserve, esp. by leaving money on the table.
Cute game btw!
[1] www.goonbee.com [2] www.github.com/lmirosevic/GBAds