Bloons Tower Defense 4

Bloons Tower Defense 4 is the entry that turned Ninja Kiwi's balloon-popping series from a flash game curiosity into a genre staple, adding the special-agent towers and heavier upgrade trees that later entries would build their entire identity around.

The trap most new players fall into is treating every bloon the same: camo bloons slip past towers that can't detect camo regardless of damage output, and lead bloons shrug off sharp projectiles entirely, needing explosive or fire damage instead. Placing a cheap detection tower near a strong damage tower solves both problems at once, and it's usually a better use of early cash than maxing out a single tower's upgrade path before your defenses can even see what's coming. Later rounds escalate fast enough that a defense built only for early bloon types collapses the moment camo and lead bloons start appearing together. If you want to see how far the series has come since, Bloons Tower Defense 6 rebuilds the same core loop in full 3D with hero towers added on top.