Multi-Tile movement, and a shuttle mechanized vehicle to use it.

code/modules/multi-tile/multi-tile.dm

@@ -0,0 +1,28 @@
+/*
+ * This is the home of multi-tile movement checks, and thus here be dragons. You are warned.
+ */
+
+/atom/movable/proc/check_multi_tile_move_density_dir(var/stepdir)
+	if(!locs || !locs.len)
+		return TRUE
+
+	if(bound_height > 32 || bound_width > 32)
+		var/safe_move = TRUE
+		var/list/checked_turfs = list()
+		for(var/turf/T in locs)
+			var/turf/Tcheck = get_step(T, stepdir)
+			if(Tcheck in checked_turfs)
+				continue
+			if(Tcheck in locs)
+				checked_turfs |= Tcheck
+				continue
+			if(!(Tcheck in locs))
+				if(!T.Exit(src, Tcheck))
+					safe_move = FALSE
+				if(!Tcheck.Enter(src, T))
+					safe_move = FALSE
+			checked_turfs |= Tcheck
+			if(!safe_move)
+				break
+		return safe_move
+	return TRUE