What upgrades are trying to solve

Every run awards resources, whether the defense wins or loses, and those resources feed a permanent upgrade tree. The useful question is not “Which node is always best?” but “What stopped the last run, and which permanent purchase changes that failure?” Exact costs, multipliers, and a universal optimal order are not established in the collected sources.

Build enough power to learn the next stage, then spend according to the bottleneck you can actually observe.

Priority 1: stabilize the opening

Gunner is the confirmed first turret, and recorded gameplay shows early investment in it. That makes a modest Gunner path the best-documented opening choice: it strengthens a tool every new player already has instead of depending on a later unlock.

Stabilizing does not mean buying every Gunner node. Stop when the opening defense lasts long enough to reveal the next problem. If a new choke, armored group, or resource shortage becomes the limiting factor, the next purchase should answer that evidence.

Priority 2: test penetration against density

Penetration appears in two independent gameplay sources and is described as a strong multiplier for working through packed enemies. It is therefore an important upgrade to test when Gunner fire is landing but the dense stream is not thinning quickly enough.

The exact multiplier and patch-specific value are To be confirmed. Penetration should be treated as a documented route, not an unconditional first purchase on every save. Compare one attempt before and after the upgrade on the same stage whenever possible.

Priority 3: balance economy and combat

Economy upgrades can shorten the path to later unlocks, while combat upgrades can push the current run farther and may also increase the reward earned from it. The correct choice depends on the current failure:

  • Choose combat when the defense collapses before you can learn the late wave.
  • Test economy when the stage is stable but progression feels resource-bound.
  • Unlock a new turret when the map needs a role the current build cannot provide.
  • Preserve flexibility when the next stage or patch is still unfamiliar.

This is a decision framework, not a hidden numerical tier list.

A three-phase spending plan

Opening: strengthen the confirmed starter tool enough to produce repeatable runs. Expansion: add the turret or ability role needed by the current route, rather than unlocking everything at once. Refinement: invest in penetration, economy, or specialized damage after the failure point is visible.

Change one branch at a time and record the result. If several upgrades are bought between attempts, it becomes difficult to know which purchase fixed the defense. A short testing loop produces more reliable priorities than copying an undated build.

Mistakes to avoid

Do not treat failure as wasted time; the game explicitly carries resources into permanent progression. Do not spend solely from an unsupported tier label, and do not assume an early recommendation remains optimal after new turrets and maps appear. Avoid quoting exact costs or damage values without checking the live build.

The safest current order is conditional: stabilize with the known starter path, test penetration when density is the problem, choose economy when resources are the bottleneck, and unlock new roles when placement alone cannot solve the stage. Anything more exact remains To be confirmed.