Alpha Mods

 are special modifiers that can be bought mid-game (and last the duration of the current game). The player needs to be rank 30 to unlock them, and to buy a mod to a tower, the player can simply double-click the tower and a small menu will appear with the alpha mods available for purchase in the right. The mods can stack (so 2 Ammo Mods increase maximum ammo by 50%) and the cost for the same mod is doubled with each purchase (1st Ammo Mod costs $2.5k, 2nd costs $5k, 3rd costs $10k), but each tower can only have 10 mods, and they cannot be sold. There are 8 types of Alpha Mods:

Ammo Mod

 * Description: Ammo Mod: Increases the maximum ammunition for towers with limited ammunition by 25%. Using a high-tech form of matter-compression, it is possible to include extra ammo rounds inside the weapon at light-speed, effectively increase the amount of ammo it can hold.
 * Stats: Maximum ammunition increased by 25%.
 * Cost: $2,500

Speed Mod

 * Description: Speed Mod: Increases refire rate by 10% and reload rate by 25%. Using ImMediat teleportation technology it is possible to transfer ammunition to the gun barrel much faster!
 * Stats: Fire rate increased by 10%; Reload rate increased by 25.
 * Cost: $3,500

Impact Mod

 * Description: Impact Mod: Increases impact force on targets. Accumulation of energy in the tip of the bullet when it is shot increases its impact abilities, rarely causing them to get stunned!
 * Stats: Pushes bloons back 15px; 5% chance of stunning bloon targets; Does not work on blimps.
 * Cost: $3,500

Area Mod

 * Description: Area Mod: Increases explosion size by 15%. Extra gunpowder and pressurized air containers inside the bullets increase the spread of the explosion by a big amount.
 * Stats: Explosive-towers only; Increases explosion size by 15%.
 * Cost: $4,500