Shooting walls can create bullet holes/dents (#30714)

* Bullet holes in walls

* Code standards, new sprite

code/__DEFINES/layers.dm

@@ -12,6 +12,7 @@
 #define HIGH_TURF_LAYER 2.03
 #define ABOVE_OPEN_TURF_LAYER 2.04
 #define CLOSED_TURF_LAYER 2.05
+#define BULLET_HOLE_LAYER 2.06
 #define ABOVE_NORMAL_TURF_LAYER 2.08
 #define LATTICE_LAYER 2.2
 #define DISPOSAL_PIPE_LAYER 2.3

code/game/turfs/closed.dm

@@ -138,3 +138,16 @@
 	desc = "A wall made out of a strange metal. The squares on it pulse in a predictable pattern."
 	icon = 'icons/turf/walls/hierophant_wall.dmi'
 	icon_state = "wall"
+
+/turf/closed/bullet_act(obj/item/projectile/Proj)
+	..()
+	if(!Proj.nodamage && (Proj.damage_type == BRUTE || Proj.damage_type == BURN))
+		var/mutable_appearance/bullet_hole = mutable_appearance('icons/effects/effects.dmi', "bullet_hole", BULLET_HOLE_LAYER)
+
+		var/random_x = rand(-13, 13)
+		bullet_hole.pixel_x += random_x
+
+		var/random_y = rand(-13, 13)
+		bullet_hole.pixel_y += random_y
+
+		add_overlay(bullet_hole, TRUE)