Background walls/draft

Background walls, also just known as walls, are tiles that create backgrounds on top of biome backgrounds. Walls are hidden behind everything else, such as blocks. Natural walls are generated at world creation, being abundant in certain biomes like the Underground Jungle, and are of the main components a Terraria world consists of alongside blocks and liquids. Walls can be removed with a hammer or . Flammable walls can also be destroyed by fire or lava. There are currently 250 obtainable walls.
Walls can be placed on any tile which does not already contain a wall, if it is adjacent to another wall or block. Placed walls are either "safe" or "unsafe".
Certain mechanics of walls are dependent on if they are "safe" or "unsafe":
* s prevent enemies from spawning (but do not prevent their passage), and a mostly unbroken background of safe walls is necessary for a structure to qualify as an NPC house, or to use a Bed to change a player's spawn point.
** Safe walls are usually obtained from crafting, or purchased from NPCs, but can also be found naturally in certain structures, such as Shrines and Pyramids. 
* s will not stop enemies from spawning, and cannot be utilized for houses.
** Most unsafe walls are naturally generated, and when broken, will either drop their safe equivalent or nothing at all.
** They can only be removed by starting from their edge (i.e., adjacent space with no wall), which for explosives means that an edge must exist somewhere within the radius of the explosion.
** Walls that are converted via biome spread or the Clentaminator/ are considered unsafe, even if they were previously safe.
** Some safe walls can be transmuted into unsafe walls by dropping them into Shimmer. These transmuted walls will be prefixed with "Cursed", "Forbidden", "Infested", or "Treacherous". Once placed, these walls will drop their "safe" form if removed by the player.
Distinguishing safe walls from unsafe walls can be tricky because many walls, such as Obsidian Brick Walls or Dungeon Brick Walls, exist in both safe and unsafe forms. With these walls (both of which are harvestable), the player must break the unsafe walls and replace them in order for them to count as safe walls. Similarly, many (or all, on ) naturally-generated walls have safe counterparts which are obtainable through crafting or purchase from NPCs. 
== Types ==
=== Crafted walls ===
These walls are made by the player using various crafting materials. All crafted walls qualify for housing.
=== Purchased walls ===
These walls are purchased from various NPCs. All purchased walls qualify for housing.
=== Harvested walls ===
These walls can be harvested in various places when exploring the world. Most of them can also be obtained through crafting. All harvested walls qualify for housing.
=== Converted walls ===
These walls are normally created by biome spread. They can also be made using Solution sprayed with the Clentaminator, and on the they can also be crafted or purchased (with the exception of the natural Mushroom Wall). On the the Clentaminator is the only way the player can make these walls. These walls qualify for housing when they are crafted or purchased, but not if they are created by biome spread or the Clentaminator.
== Shimmered walls==
These walls are transmuted by dropping them into Shimmer. Once placed, the transmuted walls are "unsafe", and do not qualify for housing. The "unsafe" walls will drop their "safe" form if removed by the player.
Input	Output
Blue, Green, Pink, Lihzahrd, Sandstone, Hardened Sand, Spider
== Notes ==
* Dirt Walls generally completely cover the background at Underground depths above zero (see Layer, Depth Meter). Placing new walls in this area would require first tearing down the existing walls starting from the top (the Surface) or the bottom (zero depth), which can be an arduous task. Alternatively, the existing walls can be destroyed using explosives.
* At depths below zero, the backdrop of the map is generally no longer covered with actual wall tiles, though this can be difficult to differentiate visually since the biome background at these depths can have a similar appearance. Walls can be placed freely here by players.
* Torches and several other furniture items can be placed directly on background walls without requiring blocks below them.
* Most walls have no coin value, even if they were crafted from rare materials. Stained glass and wallpaper bought from the Painter are exceptions.
* Walls appear to have their own placement layer.
== See also ==
* Wall IDs
* Blocks
== History ==
== Footnotes ==