Adds Multi-Z Test Map

code/datums/observation/turf_changed.dm

@@ -0,0 +1,28 @@
+//	Observer Pattern Implementation: Turf Changed
+//		Registration type: /turf
+//
+//		Raised when: A turf has been changed using the ChangeTurf proc.
+//
+//		Arguments that the called proc should expect:
+//			/turf/affected:  The turf that has changed
+//			/old_density: Density before the change
+//			/new_density: Density after the change
+//			/old_opacity: Opacity before the change
+//			/new_opacity: Opacity after the change
+
+var/decl/observ/turf_changed/turf_changed_event = new()
+
+/decl/observ/turf_changed
+	name = "Turf Changed"
+	expected_type = /turf
+
+/************************
+* Turf Changed Handling *
+************************/
+
+/turf/ChangeTurf()
+	var/old_density = density
+	var/old_opacity = opacity
+	. = ..()
+	if(.)
+		turf_changed_event.raise_event(src, old_density, density, old_opacity, opacity)