Boulder

Boulder*

Statistics

Projectile created* Boulder
* Internal Item ID: **540**
* Internal Tile ID: **138**
* Internal Projectile ID: **99**

**Boulders** are unique placeable 2×2 foreground objects, and are stationary when placed. When unsupported, they fall and begin to roll away. They pick up speed and damage players, enemies and NPCs along their path. Boulders will also begin to roll if mined with a pickaxe or drill, meaning that they cannot be picked up again once placed.

Boulders will roll across flat surfaces and down slopes, but will break and disappear on contact with an obstacle. They deal 120–160 / 240–320 / 360–480 damage to players (60–80 damage to NPCs, enemies, and critters) on contact. Boulders pierce through an unlimited number of entities.

Boulder traps occur naturally in the Underground and Cavern layers, and consist of a single Boulder in the ceiling, supported by six (2×3) Active Stone Blocks wired to Pressure Plates. If a player walks onto the Pressure Plate, the Boulder falls down and begins rolling.

## Crafting

### Used in

* Pink Gel5
* **Boulder**5
* Life Crystal

## Notes

* The Boulder's roll direction is determined by:
	+ When hit with a pickaxe or drill, Boulders roll in the direction that provides the longest roll time.
	+ Boulders always roll left; if there is no space on the left, then they roll to the right.
	+ If the Boulder cannot roll left or right, it will merely break and disappear.
	+ Boulders spawned with a Boulder Statue will roll left or right depending on whether the x coordinate of the statue is even or odd; to change the direction the Boulder rolls, move the statue left or right by one block.
* The Boulder accelerates to a maximum speed of 36 mph over the course of 2.18 seconds.
* Like all other projectiles, the Boulder will break after rolling for one minute.
	+ If moving along a flat strip of land, it can reach a maximum distance of 1559 tiles.
* Once rolling, Boulders cause the same amount of damage regardless of their speed. A player or enemy hit by a Boulder that just began rolling will take just as much damage as they would from a fast-moving Boulder. This also means that players trying to mine it while touching it will be hit.
* Boulders can be placed atop flat-surface furniture, such as bookcases, and can be stacked on each other. Mining the bottom Boulder causes all of them to fall and roll. Mining only the top Boulder causes only that one to roll off.
* Boulders can activate red, green, and yellow (NPC-sensing) Pressure Plates by rolling over them.
* Boulders are unable to fit through 2-tile high spaces in the Console version.
* It is possible for Boulders to roll uphill, as long as there is one flat block in between each sloped block.

## Tips

* In Expert and Master Modes, Boulder traps should be avoided at all costs, considering the deadly force of 280 / 420 average damage.
* At full tilt, boulders roll faster than a running player with several speed boosts applied. Using a Hoverboard or Asphalt can help to overcome them.
* Boulders are effective when used along with Grenades against The Destroyer and Eater of Worlds.
* Using Boulders is an efficient way to kill NPCs, should one wish to do that (for example, for getting their unique drops).
* Players can detect Boulder traps "in the wild" by wielding a mechanism item such as a Pressure Plate, by carrying a Mechanical Lens or its upgrade The Grand Design, or by using a Dangersense Potion. All except the last will allow the player to view placed wires, and the vertical wire with its 2×3 rectangle atop it is quite distinctive.
* Once detected, there are some basic ways to disarm them:
	+ If approaching from above, the player can mine their way toward the top of the trap, and use a pickaxe to break the boulder from outside the sealed chamber.
	+ From below, the player can make sure there is a slope downwards to the left, then trigger the plate from the right side and immediately dodge to the right.
	+ Once the player has The Grand Design (or even just a Wire Cutter), they can easily disable the trap at a distance by cutting the vertical wire.
	+ Removing the pressure plate will prevent the trap from triggering, but the Boulder will remain above, and becomes a hazard if freed from below.
* As with other traps, the mechanisms (but not the Boulder) can be harvested for later use. The pressure plate and active stone can be taken with a pickaxe, but collecting the wire needs a Wire Cutter or upgrade thereof.
	+ Once triggered, Orange Pressure Plates will break, and cannot be harvested.
* In Hardmode, the Active Stone Blocks do not change into their respective biome. Therefore, they can be much easier to spot and deactivate.

## Trivia

* Boulders are one of four non-accessories that are crafted at a Tinkerer's Workshop, the others being the Cell Phone, Multicolor Wrench, and The Grand Design.
* Boulders are one of the three (the others being Rolling Cactus and Bee Hive) placeable objects that cannot be picked up again once placed, as hammers have no effect on them, and mining them with a pickaxe or drill only causes them to roll (or destroys them, if they cannot roll).
	+ Boulders are the only placeable objects that cannot be picked up again once placed.
* Boulders are able to deal damage to Target Dummies.
* Once the Boulder has reached its maximum speed, it completes a full rotation approximately once every quarter of a second.

## History

PC version
* Desktop 1.4.4.2: Fixed Smart Cursor trying to place Boulders on Pylons.

* Desktop 1.4.4:
	+ Now used to craft Bouncy Boulder and Life Crystal Boulder.
	+ Now breaks into smaller Mini Boulders in For the worthy worlds.

* Desktop 1.4.0.1:
	+ Now crafted at a Heavy Work Bench instead of Tinkerer's Workshop.
	+ Sheeting error in placed sprite fixed.

* Desktop 1.3.2: Placed sprite updated. Old sprite was:

* Desktop 1.3.1: Item sprite updated. Old sprite was:

* Desktop 1.3.0.1: Damage from Boulders is now reduced by player defenses (Boulder damage previously ignored player defense).

* Desktop 1.2.4: Fixed the crash when a Chest is placed above but not directly on a Boulder.

* Desktop 1.2.3: Boulders with Chests on them no longer crash the game if the Boulder is hit.

* Desktop 1.2: Stack limit raised from 250 to 999.

* Desktop 1.1: Introduced.

Console version
* Console-Release: Introduced.

Nintendo Switch version
* Switch 1.0.711.6: Introduced.

Mobile version
* Mobile-Release: Introduced.

Nintendo 3DSversion
* 3DS-Release: Introduced.

## References

1. ↑ Information taken from the PC 1.4.0.5 source code, method `Check2x2()` in `Terraria.WorldGen.cs`. There may be inaccuracies, as the current  PC version is 1.4.4.9.
2. ↑ Information taken from the PC 1.4.0.5 source code, method `AI()` in `Terraria.Projectile.cs`. There may be inaccuracies, as the current  PC version is 1.4.4.9.