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In Bloons TD 6, it is important to choose the best crosspathing for a specific tower in order to receive the best benefits out of that tower type. Towers have special roles to play for each stage of the game. The Engineer Monkey in its core is to produce various contraptions in order to assist the defense.



The Engineer Monkey's earlier upgrades are designed to be a supporting role in the early-game, each fulfilling a different aspect that is not normally found with other towers. The key weaponry of the Engineer is sentries, which typically fill most of the DPS of an early-game Engineer. Its Tier 3 upgrades each provide a different later early-game role. Its later upgrades, specifically starting at Tier 4, are designed for a more defined role, Path 1 providing offense, Path 2 with support, and Path 3 with instantly destroying passing bloons. Crosspathing is somewhat for Engineer with many crosspaths having special interactions with each other.


Tier 2 and below[]

Base Tower and Tier 1 Crosspaths[]

  • 0-0-0: It has more pierce and attack speed than an unupgraded Dart Monkey, but it is only 1.5x as expensive. On some maps, even just one 0-0-0 Engineer can solo.
  • 1-0-0: Produces temporary sentries, each with the power of a 0-0-0 Dart Monkey. Cheap but effective source of extra pops.
  • 0-1-0: Gains a substantial amount of range. It helps snipe more bloons from further, and thus can be marginally useful in some cases.
  • 0-0-1: Pops many more bloons per shot and can pop Frozen Bloons. Can be used for early game cleanup.
  • 1-1-0: Combines the temporary sentries with the large extra range. But usually this serves to space them out for less concentrated DPS.
  • 1-0-1: Both the Engineer and the sentries gain extra pierce and can pop Frozen.
  • 0-1-1: Gains range and extra pierce. May be helpful if needing to survive an early-game leading into Double Gun.

Tier 2 Crosspaths[]

  • 2-0-0: Increases the rate of producing sentries. This also has an effect on higher tiers on other paths, mainly foam and bloon trap by decreasing the cooldown of those "attacks".
  • 0-2-0: Usually a stepping stone for Cleansing Foam.
  • 0-0-2: Stopping bloons with Pin is a useful early-game utility. This is the minimum for pinning a bloon in place. Crosspaths may marginally improve that pinning effect, but requires a Tier 3 crosspath to have an upgraded effect.
  • 2-1-0: Same as 1-1-0 but spawns sentries faster.
  • 2-0-1: Faster-producing 1-0-1.
  • 1-2-0: Engineer and sentries gain Deconstruction's damage bonuses to MOAB-class and Fortified. Only matters if you are planning to focus on top path upgrades.
  • 1-0-2: Doesn't give the pinning effect until 3-0-2 which is why this is usually a stepping stone.
  • 2-2-0: Engineer and faster-producing sentries gain Deconstruction's damage bonuses to MOAB-class and Fortified. Strong early-game MOAB-class popping power. Upgrading further to Sprockets will make even more use out of this potential.
  • 2-0-2: The Engineer and sentries now get both benefits of the bottom path, similarly to a 2-0-1 with the Engineer nailgun able to pin bloons. Extra pierce and the pinning effect. 3-0-2 is needed for the sentries to pin, however.
  • 0-2-1: Essentially a 0-1-1 Engineer with Deconstruction's damage bonuses to MOAB-class and Fortified. Not the best crosspath since its main attack doesn't deal a lot of damage against MOAB class bloons.
  • 0-1-2: Combines long range with the capability to pin bloons. Allows the Engineer to greatly increase the usage of the pinning effect.
  • 0-2-2: Combines long range with the capability to pin bloons and deal extra damage to MOAB-class and Fortified. It isn't much different compared to 0-1-2, other than doing a little extra damage to the aforementioned types.

Upper Path 1[]


  • 3-0-0: The non-crosspathed Sprockets can be spammed for mostly maximum numbers of hits, as Sprockets massively increases attack speed of the nailgun and sentry attacks. Crosspathing will be quite useful to make the most of Sprockets, mainly mid-game potential and anti-MOAB popping.
  • 3-1-0: Extra range for the Engineer himself will make sentries go further from the Engineer.
  • 3-2-0: Gains extra damage to MOAB-class and Fortified, and utilizes it much more with the extra attack speed of the nailgun and sentries.
  • 3-0-1: Sentries gain more pierce and so does the Engineer. The engineer and his sentries gain more attack speed with Sprockets, so even more value packed into this upgrade.
  • 3-0-2: Sentries can also pin bloons with their attacks. Generally good against bloons that spawns more than 2 children.

Sentry Expert[]

  • 4-0-0: The Sentry Expert, regardless of crosspathing, has special functionalities that other Engineers aren't sufficient alone. Its Crushing, Boom, Cold, and Energy Sentries all do special tasks dedicated for specialization at different situations. The majority of these sentries attack slower but all have quite high pierce and overall possess high damage and/or utility, from MOAB-class damage to stalling to grouped bloon destruction. Crosspathing for these sentries helps slightly for Sentry Expert but not significantly outside the mid-game where it tends to shine the best.
  • 4-1-0: Sentries already gain a sizeable amount of range already, the range buff for the sentries is insignificant, and the increased Engineer range is often worse due to how the Engineer may deploy sentries in awkwardly distant locations and in less focused areas.
  • 4-2-0: Not as useful as 3-2-0 at single-targets due to the reduced synergy with Deconstruction, but better against grouped targets due to the much greater pierce of each sentry. That being said, the best Sentry Expert sentry candidate for beating MOAB-class is Energy Sentries, which already gain a sizable MOAB-class bonus but still appreciates the Deconstruction buff. Extra Fortified damage can be useful for handling mid-game Fortified Bloons.
  • 4-0-1: More pierce for each sentry, useful for handling dense mid-game rounds. Pierce bonus for these sentries is always roughly +25%.
  • 4-0-2: Mostly the best crosspath for a practical Sentry Expert, as Sentry Experts in general are better as a mid-game support DPS option. Cleaning up weaker bloons with Sentry Expert pairs well with the Pin effect to its sentries, especially due to the high pierce of all their sentries.

Sentry Champion[]

  • 5-0-0: The non-crosspathed Sentry Champion is somewhat weaker than a crosspathed Sentry Champion, but not as significant as some of the other Tier 5 towers in the game. Crosspathing is recommended to make the most of the massive DPS in exchange for the Sentry Expert's utility and multiple specializations.
  • 5-1-0: Extra range can be helpful for the sentries, although the wider range of the Engineer himself can cause sentries to move further from his range, sometimes awkwardly. However, the 5-2-0 crosspath will outweigh this slight overall negative effect from 5-1-0.
  • 5-2-0: This is usually the best crosspath for Sentry Champion, giving +1 MOAB-class and +1 Fortified damage per sentry. Combined with the Champion Sentries' super fast attack speed and decent damage and pierce, this equates to a lot more DPS during the late-game where MOAB-class and Fortified dominate the late-game. This certainly also helps allow Champion Sentries to beat Fortified Super Ceramics more easily too.
  • 5-0-1: Gains +1 pierce, which is a bit too small for Champion Sentry's 5 pierce. Sentry self-destructive explosions don't benefit from the extra pierce. Ignore the main Engineer's nail gun attack, as it is the Champion Sentries' main attacks that do the most damage.
  • 5-0-2: The Pin upgrade helps the mid-game become easier to counter, pinning any bloon below Ceramic especially Regrows in place with ease with all Champion Sentries. Beyond Round 80, the Pin upgrade is mostly a vestige, as Pin cannot affect Ceramics or above.

Upper Path 2[]

Cleansing Foam[]

  • 0-3-0: For purely the Cleansing Foam effects, which removes Camo and Regrow as well as cleanse Leads, 0-3-0 is sufficient. Crosspathing is not essential, but either crosspath will improve its effect to different extents.
  • 1-3-0: Adds sentries that come with Cleansing Foam in each shot plus the Deconstruction bonus damage stats. The added sentries help distribute foam across a further range while being able to keep the main attack foam in the same spot. Bear in mind that the sentries must detect camo in order to act as decamo, and cannot do so by default.
  • 2-3-0: In addition to faster sentry production, it produces Cleansing Foam quicker too. This takes advantage of the base effects of foam.
  • 0-3-1: Cleansing Foams gain +5 more pierce, allowing them to sustain more bloons before expiring.
  • 0-3-2: Cleansing Foam with Pin can slow down bloons by 50% for a brief amount of time, including Ceramics. It comes in handy against Super Ceramics to reduce their progress.


  • 0-4-0: For purely the Overclock ability, this crosspath is sufficient. Crosspathing changes nothing to the ability. Overclock gains extra nail gun pierce too, making the 0-4-2 crosspath actually feel more significant for its main attacks.
  • 1-4-0: Sentries from an Overclock Engineer do not receive any benefits compared to a Cleansing Foam Engineer. Otherwise, treat these extra sentries as if the Engineer was 1-3-0.
  • 2-4-0: Sentries from an Overclock Engineer do not receive any benefits compared to a Cleansing Foam Engineer, and neither does the Cleansing Foam attack. Otherwise, treat these faster produced foamy sentries and faster Foams as if the Engineer was 2-3-0.
  • 0-4-1: Just like 0-3-1 Cleansing Foam, but the nail gun's pierce bonus is insignificant.
  • 0-4-2: Takes advantage of the much greater nail gun pierce and therefore the Pin effect can be optimized with this crosspath. Slowdown foam is similar with normal Cleansing Foam.


  • 0-5-0: For purely the Ultraboost ability, this crosspath is sufficient. Crosspathing changes nothing to the ability. Ultraboost gains even more nail gun pierce, but compared to its extraordinarily high cost it is insignificant.
  • 1-5-0: Same principles as 1-4-0.
  • 2-5-0: Same principles as 2-4-0.
  • 0-5-1: Basically takes principles from the 0-4-1 Overclock.
  • 0-5-2: Basically takes principles from the 0-4-2 Overclock.

Upper Path 3[]

Double Gun[]

  • 0-0-3: Double Gun can hold its own in the late early-game till mid-game pretty well, thanks to the doubled attack speed of its pinning nailgun attack. However, crosspathing should focus on applying the Pin effect as much as possible.
  • 1-0-3: Sentries produced from Double Gun are statistically equivalent to 1-0-1 Engineer sentries. Despite having the Pin upgrade, sentries do not pin unless given Sprockets or above. Merely, these sentries add extra popping power.
  • 2-0-3: Adds the maximum extra popping power for Double Gun by producing more sentries per second.
  • 0-1-3: This allows Double Gun to apply the Pin effect to bloons that are much further away from them.
  • 0-2-3: Generally a waste of money due to the fact that its main attack isn't made for popping M.O.A.B. Class bloons.

Bloon Trap[]

  • 0-0-4: This upgrade summons a trap that sucks in any visible non-blimp bloon. Once full, the player can hover on the trap to get some money. Since crosspaths have only minor impact on the efficiency of Bloon Trap, specifically from 2-0-4 and 0-1-4, crosspathing isn't the most important aspect of Bloon Trap.
  • 1-0-4: Does nothing except add sentries. Can be wasteful because fewer bloons go into the trap and therefore empty less soon.
  • 2-0-4: Even though it allows traps to be deployed much faster, this upgrade is generally not preferred because it tends to do the opposite of what the Bloon Trap wants, which is to let bloons go into the trap, but the sentries that spawns prevent some bloons from getting into the trap and therefore make less money overall. Make sure the traps spawncamp the bloons, or else the extra sentries made become an extra hassle to eliminate for maximizing money gains.
  • 0-1-4: Since 29.0, this upgrade has generally become the preferred crosspath, as it grants the Engineer extreme flexibility thanks to the trap being able to be placed anywhere with its range. Considering that range is also extremely large, this means the Engineer can be significantly far away from the trap and still reap the benefits.
  • 0-2-4: Doesn't really help since its main attack isn't very good at taking down blimps anyways, though allowing fortified leads/ceramics so as not to consume as much RBE can be useful in some situations.

XXXL Trap[]

  • 0-0-5: XXXL Trap upgrades the traps into much larger traps that can trap any blimp other than BADs and Bosses. The traps refresh significantly quicker too, making it easier to use as a source of main DPS or as a last ditch defense.
  • 1-0-5: Similarly to 1-0-4 Bloon Trap, all that 1-0-5 XXXL Trap does compared to its uncrosspathed variant is add sentries, which can be wasteful if trying to opt for maximum trap efficiency.
  • 2-0-5: Reduces the cooldown between trap placements by a multiplier of *0.6 (+66.66% attack speed). Sentries don't backfire as badly since XXXL Trap's main prey consists of ceramics or stronger, which low tier sentries are ineffective against. Not frequently used over 015 XXXL Trap as the middle crosspath can already effectively reach its deployment speed cap with Overclock and Jungle Drums.
  • 0-1-5: Just like 0-1-4 Trap, 0-1-5 XXXL Trap is now more preferable to 2-0-5 in almost all situations due to being able to micro the positions of traps, and the lost speed from 2-0-5 is compensated by using Overclock and Jungle Drums to almost cap out trap deployment speed. Also note that MOAB-class bloons have a much larger hitbox, making it able to catch blimps even further away.
  • 0-2-5: Since 36.0, this crosspath can see use for being able to take in more fortified bloons at once, as the trap will now ignore fortified effects of any MOAB-class bloons that enter it. Particularly the best crosspath for this upgrade.