diff --git a/src/main.rs b/src/main.rs
index efe06a1..40e4cf7 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -384,14 +384,16 @@ impl State {
         }
 
         // Build a new map and place the player
-        let worldmap;
+        let mut builder = map_builders::random_builder();
+        let mut worldmap;
         let current_depth;
         let player_start;
         {
             let mut worldmap_resource = self.ecs.write_resource::<Map>();
             current_depth = worldmap_resource.depth;
+            // builder = map_builders::random_builder(current_depth + 1);
 
-            let (newmap, start) = map_builders::build_random_map(current_depth + 1);
+            let (newmap, start) = builder.build_map(current_depth + 1);
 
             *worldmap_resource = newmap;
             player_start = start;
@@ -399,9 +401,7 @@ impl State {
         }
 
         // Spawn bad guys
-        for room in worldmap.rooms.iter().skip(1) {
-            spawner::spawn_room(&mut self.ecs, room, current_depth + 1);
-        }
+        builder.spawn_entities(&mut worldmap, &mut self.ecs, current_depth + 1);
 
         // Place the player and update resources
         let (player_x, player_y) = (player_start.x, player_start.y);
@@ -445,11 +445,12 @@ impl State {
         }
 
         // Build a new map and place the player
-        let worldmap;
+        let mut builder = map_builders::random_builder();
+        let mut worldmap;
         let player_start;
         {
             let mut worldmap_resource = self.ecs.write_resource::<Map>();
-            let (newmap, start) = map_builders::build_random_map(1);
+            let (newmap, start) = builder.build_map(1);
 
             *worldmap_resource = newmap;
             player_start = start;
@@ -457,9 +458,7 @@ impl State {
         }
 
         // Spawn bad guys
-        for room in worldmap.rooms.iter().skip(1) {
-            spawner::spawn_room(&mut self.ecs, room, 1);
-        }
+        builder.spawn_entities(&mut worldmap, &mut self.ecs, 1);
 
         // Place the player and update resources
         let (player_x, player_y) = (player_start.x, player_start.y);
@@ -534,15 +533,14 @@ fn main() -> rltk::BError {
 
     gs.ecs.insert(SimpleMarkerAllocator::<SerializeMe>::new());
 
-    let (map, player_start) = map_builders::build_random_map(1);
+    let mut builder = map_builders::random_builder();
+    let (mut map, player_start) = builder.build_map(1);
     let (player_x, player_y) = (player_start.x, player_start.y);
 
     let player_entity = spawner::player(&mut gs.ecs, player_x, player_y);
 
     gs.ecs.insert(rltk::RandomNumberGenerator::new());
-    for room in map.rooms.iter().skip(1) {
-        spawner::spawn_room(&mut gs.ecs, room, 1);
-    }
+    builder.spawn_entities(&mut map, &mut gs.ecs, 1);
 
     gs.ecs.insert(map);
     gs.ecs.insert(Point::new(player_x, player_y));
diff --git a/src/map_builders/mod.rs b/src/map_builders/mod.rs
index cd7621b..bbc68c6 100644
--- a/src/map_builders/mod.rs
+++ b/src/map_builders/mod.rs
@@ -4,11 +4,14 @@ mod simple_map;
 use crate::{Map, Position};
 use common::*;
 use simple_map::SimpleMapBuilder;
+use specs::prelude::*;
 
-trait MapBuilder {
-    fn build(new_depth: i32) -> (Map, Position);
+pub trait MapBuilder {
+    fn build_map(&mut self, new_depth: i32) -> (Map, Position);
+    fn spawn_entities(&mut self, map: &Map, ecs: &mut World, new_depth: i32);
 }
 
-pub fn build_random_map(new_depth: i32) -> (Map, Position) {
-    SimpleMapBuilder::build(new_depth)
+pub fn random_builder() -> Box<dyn MapBuilder> {
+    // Note that until we have a second map type, this isn't even slightly random
+    Box::new(SimpleMapBuilder {})
 }
diff --git a/src/map_builders/simple_map.rs b/src/map_builders/simple_map.rs
index 20f6348..010a5a8 100644
--- a/src/map_builders/simple_map.rs
+++ b/src/map_builders/simple_map.rs
@@ -1,16 +1,24 @@
 use super::{apply_horizontal_tunnel, apply_room_to_map, apply_vertical_tunnel, MapBuilder};
+use crate::spawner;
 use crate::{Map, Position, Rect, TileType};
 use rltk::RandomNumberGenerator;
+use specs::prelude::*;
 
 pub struct SimpleMapBuilder {}
 
 impl MapBuilder for SimpleMapBuilder {
-    fn build(new_depth: i32) -> (Map, Position) {
+    fn build_map(&mut self, new_depth: i32) -> (Map, Position) {
         let mut map = Map::new(new_depth);
         let playerpos = SimpleMapBuilder::rooms_and_corridors(&mut map);
 
         (map, playerpos)
     }
+
+    fn spawn_entities(&mut self, map: &Map, ecs: &mut World, _new_depth: i32) {
+        for room in map.rooms.iter().skip(1) {
+            spawner::spawn_room(ecs, room, 1);
+        }
+    }
 }
 
 impl SimpleMapBuilder {