Bloons TD6 is a tower defence game involving monkeys vs balloons for some reason. The presentation is the typical mobile game interface, and has upgrades with in-game currency, as well as real-world currency.
The monkeys are categorised into the categories: primary, military, magic, support, and then there is a unique special hero which you select beforehand in the main menu.
The military units seem very overpowered. The helicopter has free movement, is fast, attacks fast, and can be upgraded to attack all balloons. The Sniper can shoot right across the map, he attacks fairly slow though but can be sped up with upgrades.
Each (non-hero) unit has 3 upgrade paths, but you can only choose to invest in 2, but can only maximise one of them. This can drastically change the effectiveness of the unit. By default, the unit targets the first balloons, but you can switch their behaviour to target close/strong/first/last etc. Some projectiles can be upgraded to pierce multiple balloons at once, stronger ones destroy many “layers”, and some can damage the special balloons.
The special balloons can be camo which are immune to units that can’t detect them, lead are basically armoured and are immune to non-explosive/heat damage. Purple are immune to magic, white are immune to cold, and black are immune to explosions. Heart shaped balloons regenerate layers so need repeated damage.
There's loads of maps which are quite varied, then there's 3 difficulties, and then many game modes. Each game takes a long time to play through so there's an insane amount of hours required to really experience everything here.
Once you get used to the mechanics, I found many maps to be easy for the most part, but then certain waves will have a massive spike which can often catch you out. So you can go from full health to zero in just one wave. There's always a certain point where you need to have units that can attack lead balloons, then camo balloons, then the MOAB airships. This can be frustrating when you have played for 20 mins then just get destroyed without much warning.
Many of the initial maps on the normal difficulty just play exactly the same. Instead of having set squares you place units into, you can place them freely, which means you often just cram in loads of monkeys at the entrance. Even though there's usually plenty of space, you often don't need many monkeys because they are often powerful. The latter rounds, and the harder difficulties can throw an insane amount of balloons your way.
The maps that seem the hardest are the ones with multiple entry points because you often have to even out your defence or try to locate a choke point. When you have no warning where the MOAB airships are gonna enter from, it can be pure luck if you placed enough defence in the correct section. There’s maps that can be cluttered with other objects, or have elevation, so this restricts where you can place your units, or restricts their range.
When you fail, you can pay some of your monkey cash, to restore your health and get a small boost of coins. Sometimes you can basically brute force your way through some of the hard levels as long as the next towers you place make a difference (and if you have a stockpile of monkey cash - [you can always buy more with real cash!]).
There’s a bit of a learning curve, and you need to initially unlock the units, but just like most tower defence games, it is highly addictive.