Recommended order: resource gain and core damage → one dependable damage tower → slow/control → rear cleanup → map-specific Laser or Cannon upgrades → abilities and achievement-specific branches.
The first-clear route
- Secure basic income and universal value. Prioritize affordable resource and general combat upgrades that improve every run. Do not sink all early currency into an achievement-only branch.
- Raise one reliable damage platform. Community release guides favor Cannon for dense lane clearing and Gunner for dependable sustained fire.
- Unlock and strengthen control. Slow Grenades repeatedly appear in Level 6.1, Level 6.2 and Overkill routes because keeping a crowd inside the kill zone multiplies every other tower's value.
- Build a cleanup layer. Tesla Coils are consistently placed behind the main damage line. Upgrade them enough to catch leaks without making them the only answer to the full horde.
- Branch for terrain. Upgrade Laser when a map offers good bounce walls and long gates; upgrade Cannon when traffic forms straight, dense lanes.
Priority by combat role
| Priority | Role | Community-supported choices | Why it matters |
|---|---|---|---|
| High | Lane damage | Cannon, Gunner | Reliable value on most terrain and dense traffic. |
| High | Cleanup | Tesla Coil | Fast 360-degree coverage for isolated leaks behind the line. |
| High | Control | Slow Grenade | Keeps targets inside Cannon, Laser and Flamethrower coverage. |
| Medium | Terrain power | Laser | Extremely strong when flat walls create repeated bounces and gates. |
| Medium | Amplify | Flamethrower | Prepares or chips targets before the main damage line. |
| Situational | Redirect | Mortar | Can hold a side passage, but knockback needs careful aiming. |
This is an editorial route, not an official tier list
The developer has not published full release stats or an official upgrade order. Community testing also shows that terrain changes the value of Laser and explosive knockback. Treat this as a stable first-clear route, then adapt to the map.
When to buy abilities
Abilities are valuable for no-tower objectives, emergency leaks and Overkill, but several late achievements explicitly prohibit abilities. If your immediate goal is Four-tified, Specialist or Triple Threat, tower upgrades provide more direct value. If your goal is Fine, I'll Do It Myself or Overkill, move the relevant ability branch forward.
Achievement-specific detours
- Overkill: unlock Nuke and Cryo Beam access, then use crowd control to build one dense target mass.
- Elemental Carnage: invest in Flamethrower and Tesla Coil; Cryo Beam is the only allowed active tool named by the objective.
- Four-tified: strengthen four complementary tower roles rather than four overlapping damage towers.
- Fully Loaded: it is the endpoint of the tree, not a reason to spread early resources too thin.