Bloons.io

Bloons.io is a .io game, based off the game Bloons Tower Defense 6.

Mechanics
Bloons (non-MOAB) are dispersed throughout the circular map. However, they are not evenly spread, as stronger bloons spawn the closer you are to the center of the map. Note that these bloons will "chase" after players. Players start off as a 0/0/0 Dart Monkey, spawned on the outskirts of the map. Players can earn XP by popping bloons, and players can buy upgrades by spending XP (and yes, they will be deducted to price) or switch tower (which costs large amounts of XP). However, in this game you are allowed to own more than 5/2/0 upgrades (up to 5/5/5). Be careful, though, as bloons which crash into you will take away health, and the higher the RBE, the higher the damage (although you can upgrade max health by spending XP). To kill players, you don't exactly shoot them with your darts, but you shoot bloons towards them by pressing W (which costs XP). When they are killed, the game will refund all upgrades (but not tower types) at an 80% efficiency rate. The attacker gets 40% plus all of the victim's unspent XP, while the victim gets the other 40%. Tower types are saved in the victim if he respawns.

A circle with diameter 1/4 the diameter of the map is placed at the centre of the map. MOAB-class bloons (or bosses) will spawn here. They will have slightly more intelligent AI than non-MOABs, and some may have attacks.