Spike Factory

The Spike Factory is a special tower that, once placed, produces Road Spikes that pop bloons and disappear at the end of each round. Its special attack, Spike Storm, is capable of killing large amounts of bloons, destroying even MOABs and BFBs in sufficient quantity. Like the Dartling Gun, the Spike factory was not included in the original edition of the game, and does not have a hotkey. The tower was released on September 8th, 2011. It costs 595 on easy, 700 on medium, and 755 on hard. It was removed in BTD5 and will come out as an update.

Bloons TD 4 Description
"Generates piles of roadspikes around the track automatically. Leftover spikes disappear at the end of each round."

Starting Ability
Before being upgraded, the Spike Factory shoots out clumps of five tacks at a rate of one shot nearly every three seconds (per second if fast-forwarded). These clumps always land in corners and disappear at the end of each round.

Increased production
This upgrade increases the rate of how fast the Spike Factory shoots out tacks.

This costs 595 on easy, 700 on medium and 755 on hard.

Bigger Stacks
The factory produces ten spikes at a time instead of five.

This costs 510 on easy, 600 on medium and 650 on hard.

White hot spikes
Gives spikes the ability to pop frozen and lead bloons.The Tower turns purple.

This costs 300 on easy, 350 on medium and 380 on hard.

Spike Storm
Every 15 seconds the factory spreads short-lived road spikes across the entire track.The Tower turns red.

This costs 5950 on easy, 7000 on medium and 7560 on hard.

Trivia

 * If the Spike Factory is placed far enough from the track, the Road Spikes it produces will not be seen.
 * It is possible to beat the entire game with only this tower because they can pop lead and camo bloons.
 * Sometimes the Spike Storm will only cover 1/4-1/2 of the track.
 * In Bloons TD 4 Expansion, the Spike Factory's logo in the "shop" is a Dart Monkey along with the Dartling Gun.
 * It is odd that there isn't a Spike Factory in BTD5.