Bloons Tower Defense 4 is one of the most addicting flash games I've ever played.
The Goal of the game is to protect the end of the level from Bloons (balloons). These bloons' health and abilities depend on thier color.You pop these bloons with units, varying from monkeys, planes, canons, spikes, mortars, mages, glue, super monkeys, etc. Every few levels, theres a boss, which is a blimp.Each units have upgrades, like shooting faster, wider rage, explosive darts, freezing, glueing, , tornadoes, rings of fire.
Red bloons are slow and need 1 hit, blues need 2, yellow is faster and needs 3, Pink needs 4 and is even faster, Black is slow and needs 5 hits. Light blues arelike black ones, but are ice resistent.Rock covered needs alot of hits. Metal bloons are spike resistent. Camo bloons cant be seen unless a nearby unit has upgrade to do so.
This game can be nearly impossible at times, but difficulty makes game fun too.