Crawler

The Crawler is a disposable ground unit that advances toward enemy targets and self-destructs on death to inflict a large area explosion. It is a Tier 1 combat unit produced from ground unit factories and is used as a cheap, high-area damage kamikaze option to break enemy lines, destroy structures, or disable concentrations of units. The explosion is implemented in the game as an instant-firing bullet that immediately despawns and applies area damage around the unit when it dies.

Crawlers have modest health and high explosive output for their cost. Over several builds their health and explosion values were adjusted; as of the latest documented changes a single Crawler deals 80 area damage with an approximate radius of 5.5 tiles and has middling durability appropriate to single-use roles. Their weapon is set to trigger on death, so they detonate whenever they are destroyed or otherwise killed. Crawlers always explode and cannot be prevented from detonating once they die.

Crawlers interact predictably with terrain and defenses. They cannot move through completely walled bases, and cheap blocking structures such as Junctions or small Copper Walls will stop or delay them and can force them to detonate earlier. They do not detonate automatically on conveyors (a past bug was fixed), and they no longer detonate simply by being placed on conveyors. In the code the explosion is modeled as a bullet spawned at death that applies AoE damage instantly.

Practical usage and counterplay:

• Use Crawlers en masse to overwhelm static defenses by producing many cheap suicide units; schematics that continuously produce Crawlers are effective in Sand Floor maps where required resources can be produced easily. Large Crawler armies can reliably destroy production buildings and Cores if unsupported defenses are lacking.
• Crawlers are effective when ground-targeting turrets are limited; pair them with other unit types to exploit gaps in long-range defensive coverage.
• Against AI or unprepared bases, place a sacrificial line of cheap blocks (e.g., Copper Walls or Junctions) about seven tiles ahead of your main defenses to force Crawlers to detonate before reaching critical structures; repair these blocks between waves.
• Long-range splash turrets such as Ripple or fast-targeting Arcs destroy or detonate Crawlers prematurely and are effective counters. Scatter-like anti-air tools are less relevant because Crawlers are ground units.
• Player-controlled Crawlers can be steered to avoid premature detonation and to sacrifice themselves intentionally on high-value targets, making them more potent in PvP when micro is available.
• Crawlers cannot sustain prolonged sieges alone; higher-tier units (Nova, Flare, and T2 options) are recommended for direct assaults on fortified positions, while Crawlers serve as economical adjuncts for map control and base disruption.

Development notes and trivia:

• The Crawler was originally added in older builds and has had multiple balance changes: health and explosion values were increased and decreased across updates, its speed was set to a concrete tiles/second value, its weapon was changed to trigger on death, and its production source moved to the Ground Factory.
• Crawlers are the only unit documented to require coal for research in some tech trees.
• In the game code the explosion is implemented by spawning an ephemeral bullet on death that immediately applies AoE damage, which is why the unit appears to "fire" on death.