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Spike Factory gains special targeting priority and accelerated production at the start of each round.
~ BTD6 description

Smart Spikes (Directed Spikes before version 14.0) is the second upgrade of the third path for the Spike Factory. It grants quadrupled production speed to the tower for 2.5 seconds every start of each round, and allows the Spike Factory to have target priorities. The target priority is initially set to Normal, its normal target priority, but it can be changed to a unique target setting to make best use of this upgrade.

Besides new unique target priorities and quadrupled production speed at the start of the round, Smart Spikes provides Spike Storm with a special crosspath benefit, allowing the Spike Storm ability to only target active lanes, as well as giving an exclusive attack speed benefit via the Smart Spikes' start-of-round attack speed bonus.

It costs $340 on Easy, $400 on Medium, $430 on Hard, and $480 on Impoppable.



Spike Factory with Smart Spikes receives a pair of gears, one on each opposing side, and are placed partially outside of the Spike Factory itself, extending from each side of its body at the top section. The gears regularly rotate into the direction of the Spike Factory's centrepoint.


Smart Spikes gains special targeting priorities: Close, Far, and Smart. In addition, the Spike Factory produces spikes 4x faster at the start of each round. Special interactions for Spike Storm and Carpet of Spikes abilities are granted, having an exclusive self-synergy with the start-of-round benefit and sets the storms of spikes to target only the active lanes.

Its attack speed boost can only occur once the upgrade is bought before the round begins. Such a temporary speed boost is considered a Charge Charge (unspecified appliable boost), which Gravelord Lych can prey on.

Targeting Priorities[]

Smart Spikes defaults on Normal targeting priority, which dispenses the spikes onto nearby bloon track in a semi-sporadical behavior. With this upgrade, it will also receive Close, Far, and Smart.

  • Normal: Targets spike piles in a somewhat sporadical way, spreading spikes as evenly as possible within its range.
  • Close: Targets the closest region(s) of track within range.
  • Far: Targets the furthest region(s) of track within range.
  • Smart: Prioritizes the track with the Bloon the farthest through it, then targets the spot on that track closest to the exit.



Smart Spikes is a rather situational but also useful upgrade to pick for the Spike Factory, as it sacrifices either stronger spike piles (Path 1) or faster production (Path 2) for special targeting of spikes. On most situations, random targeting is sufficient for the Spike Factory to produce maximized spike production, in order to stockpile spike piles everywhere within the tower's radius. However, there are few situations where it would be worth sacrificing one of the paths for allowance of specialized but limited custom spike pile placement. Places where there are multiple paths or intersections on the map are generally wise choices to crosspath a Spike Factory with Smart Spikes.

Along with crosspathing to Smart Spikes, there is the opportunity to further upgrade to Long Life Spikes to make even better use of Smart Spikes. When pursuing further towards Path 3, stockpiling because even more vital for optimizing its performance. Learning the ways of stockpiling spikes effectively is especially important for the final upgrade Perma-Spike.

Before considering purchasing Smart Spikes, consider if it's possible to maximize the potential of a Spike Factory without Smart Spikes. It is worth analyzing the map if it is possible to avoid overscattering of the spike piles due to multiple paths. If so, it is better off going for just Path 1 and Path 2, unless going for Perma-Spike. When setting up the Spike Factory with Smart Spikes, provided that prior Spike Factory optimization analysis was done, consider a spot where the Spike Factory should be able to dispense spike piles specifically at. Intersections are generally the best choices for Smart Spikes to go for, as they will overcome the other Spike Factory weaknesses the most.

The one other major factor to note for the Smart Spikes upgrade is how this upgrade generates a brief production speed increase for 2.5 seconds before the start of each round. This can be handy in a very few scenarios, such as whenever there are many fast bloons at the start of each round. For most occasions, though, this upgrade mechanic is fairly small in comparison to the other Spike Factory crosspaths.

Pairing this upgrade as the crosspath for Spike Storm adds special benefits for that upgrade. More importantly, the ability can now only target lanes that bloons will travel through, making the 0-4-2 crosspath useful on certain maps. Even without this benefit, activating the ability right when the round starts can help trigger many more total spikes during the ability.


  • This upgrade is useful for specifically placing spikes along specified points, particularly so for targeting onto intersection points.
    • Avoid using the Normal targeting option unless it is to roughly determine the spike pile load.
    • Use the Close targeting option for maps where there are closeby intersections, such as on Chutes, Rake, and High Finance. Close targeting is also very useful for letting the Spike Factory distribute spikes as close towards the end of the track as possible while at the same time avoiding contact from other lanes, particularly on maps such as Firing Range, Haunted, or KartsNDarts.
    • Use the Far targeting option for maps where there are far away intersections, such as on Adora's Temple, Spring Spring, or Infernal.
    • Using the Smart targeting option is a great option for stockpiling spikes. Use this priority with stalling support to maximize the size of the spike pile.
  • The brief 4x attack speed for 2.5s at the start of each round becomes handy for preparing against fast bloons.
  • Take care when using target priorities if the Spike Factory is influenced by range buffs such as from Monkey Village or Alchemist brews. Try testing on Sandbox Mode for where the spikes may end up on certain target priorities when certain range buffs are added for the Spike Factory.

Version History[]

Gaining special target priorities alone was insufficient to encourage Path 3 crosspathing for the Spike Factory. Updates have added more adjustments to this upgrade to benefit Path 3 crosspathing in combination with higher-level upgrades.

  • Change Directed Spikes renamed to Smart Spikes.
  • Buff Tower gains quadrupled production speed for the first 2.5 seconds of each round.
  • Buff Adding Smart Spikes to Spike Storm now allows the Spike Storm ability to only target active lanes (e.g. Bloody Puddles).
  • Change Affected by Spike Factory crosspath speed changes.
  • Change [undocumented] "Smart" targeting priority now places spikes as far back on the track as it can rather than as far forward to the first bloon.
Due to a number of performance concerns, the ability for the Spike Storm factory will no longer be able to benefit from a denser storm of spikes via stacking speed buffs on the base tower.
~ Ninja Kiwi, referring to removing all Spike Storm attack speed benefits
  • Nerf Smart Spikes no longer gives start-of-round speed increase for Spike Storm ability and Carpet of Spike passive and active abilities
While we feel speed interactions for Spike Storm was a necessary evil for performance related concerns, we did not want to kill off self synergy contained local to the tower, so we are trying out an exception to this rule for the 042 crosspath. [..]
~ Ninja Kiwi, referring to 0-4-2 Spike Storm
  • Buff 042 Spike Storm ability will benefit from the xx2 crosspath start of round speed increase



Official artwork[]


  • This upgrade is one of two target-granting upgrades in BTD6 that will not automatically set one of the new target settings, with the other one being Bloon Area Denial System.
  • Internally, the upgrade icon's filename for Smart Spikes uses the old name as part of its filename: "DirectedSpikesUpgradeIcon.png".
  • The concept for the original Smart Spikes upgrade is most likely inspired by a game suggestion written on Bloons Wiki regarding adding target priorities for the Spike Factory, as shown on this page link on October 23rd 2015, although the "Normal" targeting option was named "Random" while the "Smart" targeting option was named "Attack" and had a less refined attack algorithm.
  • Before Version 24.0, the Spike Factory set on Smart would attack bloons by dispersing spikes directed at the bloon either as most close to the entrance as possible if no bloons are detected within its radius or directly at bloons. Before then, this setting would've made a good target priority for anti-stalling, but it made little sense for a tower designed around stockpiling instead of pure offense. This was changed in Version 24.0.
    • The old "Smart" target setting could detect incoming camos, as indicated by the fact that it would still stockpile spikes on the path of anticipating camo bloons, as if the camo bloons were normal bloons. This was in spite of the Spike Factory not yet counting as camo detection range for the Monkey Sub's Advanced Intel upgrade.