This is a fun Tower Defense game, but I'd say it's average even though it does have some progressive features unlike the other Bloons Tower Defense series games.

You play as the guy or gal (or perhaps a Monkey God, Commander, General or something?) who puts the towers and the monkeys to fight against the evil Bloons. I don't know what's so evil about Balloons or Bloons, I guess they just got tired of kids and their balloons somehow.

Every time you pop a Bloon, you get some XP. With that XP, you gain level (named Rank here) and unlock towers. You also unlock tower upgrades with it, I guess this just makes you wanna play the game some more...

The tower upgrades are rather fun, they give your monkey or tower a new look, but sometimes it's very minimal like the Dart Monkey's first two upgrades. After you get to the 4th upgrade, you get to choose two upgrade routes. Don't like having a choice of upgrade routes myself, maybe one of you do. Also, not all the upgrades are very descriptive, such as the Tack Shooter's third upgrade, which says it makes them shoot sawblades instead of tacks, but doesn't say what effect it really does except a visual one. Maybe it's just obvious that it increases damage, but still.

There is not a huge variety of maps to choose from, but it's alright. Not all maps are the same, some have special styles and so on, but I didn't find them too interesting.

There's an ingame save system, you can save and play that map at that time any time.

The difficulty system is simple, just make things cheap, have more lives and have less tracks on easy, while on Hard it's the reverse. Nothing much to say about this difficulty system.

Now, the music is just boring, it's the same repetitive song again and again, it gets on your nerves after hearing it 4 times or so. I'd recommend you disable music and listen to something else or nothing at all, unless you actually do like the music.

The worst part is the premium content. Sure, it's a little bit of Kreds but it just makes the game boring and less challenging. I guess it's for people that just like to play stuff in peace with no challenge, but I don't really like it at all. The worst part of the worst part is that there are some maps you have to pay to play them. That sucks. I'd understand you'd pay for something like Frag Bombs instead of the regular Bombs and for a Dreadnaught instead of a little ship that shoots darts, but maps? Come on now. I think this is an asshole move of Ninja Kiwi's.

In summary, I'd say it's a very fun game if you love Tower Defense games, it's a good game if you're a person who likes or doesn't mind Tower Defense games. Though it's not very interactive or immersive, so if you want something like that, find somewhere else.