You can play Copter.io in a99.io as unblocked.
In the Copter.io game, you have to shoot and destroy the slots that come to you and score points. You will level up after a certain time and you can choose from features such as Player Speed, Health Regen, Max Health, Armor, Fire Rate, Bullet Speed, Bullet Damage, Bullet Size. Be wary of your opponents. Try not to die.