Exactly right, people should have a look at Candy Crush as well,...

Exactly right, people should have a look at Candy Crush as well, it is possibly the most famous mobile apps, brings in (after a 3 second research) roughly $2.2m a day according to thinkgaming.com, and that's just the candy crush app itself, they have probably 5+ spin off games that bring in heaps as well, similar to Clash of Clans with their spin off Clash Royale which is hugely successful.

I used to play Candy Crush and I currently play Clash Royale (my clan that I'm the founder and leader of is actually ranked in the top 200 in Australia, so I'm pretty into my mobile games).

You'll notice the best mobile games are games that are free to play and free to advance. Candy Crush for example you can pay for boosts, and you can pay to unlock the next area rather than waiting 3 days to unlock the next area (for those that are unaware, there's like 10 levels per area in Candy Crush, most the time you can beat all 10 levels in a day, then it's 3 days to wait for the next area to unlock if you don't pay for the next area). Clash Royale is a similar structure with it being free to play but a lot faster if you spend money on it.

If you're wondering why I'm a big mobile app player, it's because I got into it when I was doing FIFO, anyone who has done that before will understand. You just have to kill time sometimes. Some of my work colleagues actually dropped $50+ per day on same of those apps, just ridiculous. I've personally probably spent $100 total on mobile games over a period of about 3 years, so nothing in comparison.

Back to my point, Candy Crush, Clash Royale etc, all free to play, free to advance, no in game ads, but if you want to advance quicker it costs money. These are very popular and profitable games and if Crazy Defence Heroes is using a similar structure, I wouldn't be concerned at all. If anything I think that makes the game more viable than if it were riddled with ads and costs. I personally don't play games with ads. I haven't had a chance to play CDH as I have an android but I'll try to play it at some point and weigh in my thoughts.