diff --git a/src/components.rs b/src/components.rs
index e94376c..5f17e23 100644
--- a/src/components.rs
+++ b/src/components.rs
@@ -1,4 +1,4 @@
-use rltk::{RGB,Point};
+use rltk::{Point, RGB};
 
 use specs::prelude::*;
 
@@ -20,6 +20,7 @@ pub struct Player {}
 
 #[derive(Component)]
 pub struct Viewshed {
-    pub visible_tiles : Vec<Point>,
-    pub range : i32
+    pub visible_tiles: Vec<Point>,
+    pub range: i32,
+    pub dirty: bool,
 }
diff --git a/src/main.rs b/src/main.rs
index e28ea87..a49b1a1 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -17,17 +17,19 @@ pub struct State {
     ecs: World,
 }
 
-fn try_move_player(delta_x: i32, delta_y: i32, ecs: &mut World) {
+pub fn try_move_player(delta_x: i32, delta_y: i32, ecs: &mut World) {
     let mut positions = ecs.write_storage::<Position>();
     let mut players = ecs.write_storage::<Player>();
+    let mut viewsheds = ecs.write_storage::<Viewshed>();
     let map = ecs.fetch::<Map>();
 
-    for (_player, pos) in (&mut players, &mut positions).join() {
-        let x = min(79, max(0, pos.x + delta_x));
-        let y = min(49, max(0, pos.y + delta_y));
-        if map.tile_at(x, y) != TileType::Wall {
-            pos.x = x;
-            pos.y = y;
+    for (_player, pos, viewshed) in (&mut players, &mut positions, &mut viewsheds).join() {
+        let destination_idx = map.xy_idx(pos.x + delta_x, pos.y + delta_y);
+        if map.tiles[destination_idx] != TileType::Wall {
+            pos.x = min(79 , max(0, pos.x + delta_x));
+            pos.y = min(49, max(0, pos.y + delta_y));
+
+            viewshed.dirty = true;
         }
     }
 }
@@ -141,9 +143,28 @@ fn main() {
         .with(Viewshed {
             visible_tiles: Vec::new(),
             range: 8,
+            dirty: true,
         })
         .build();
 
+    for room in map.rooms.iter().skip(1) {
+        let (x, y) = room.center();
+        gs.ecs
+            .create_entity()
+            .with(Position { x, y })
+            .with(Renderable {
+                glyph: rltk::to_cp437('g'),
+                fg: RGB::named(rltk::RED),
+                bg: RGB::named(rltk::BLACK),
+            })
+            .with(Viewshed {
+                visible_tiles: Vec::new(),
+                range: 8,
+                dirty: true,
+            })
+            .build();
+    }
+
     gs.ecs.insert(map);
 
     rltk::main_loop(context, gs);
diff --git a/src/visibility_system.rs b/src/visibility_system.rs
index 8dcfd7e..89c7d56 100644
--- a/src/visibility_system.rs
+++ b/src/visibility_system.rs
@@ -19,22 +19,26 @@ impl<'a> System<'a> for VisibilitySystem {
         let (mut map, entities, mut viewshed, pos, player) = data;
 
         for (ent, viewshed, pos) in (&entities, &mut viewshed, &pos).join() {
-            viewshed.visible_tiles.clear();
-            viewshed.visible_tiles = field_of_view(Point::new(pos.x, pos.y), viewshed.range, &*map);
-            viewshed
-                .visible_tiles
-                .retain(|p| p.x > 0 && p.x < map.width - 1 && p.y > 0 && p.y < map.height - 1);
+            if viewshed.dirty {
+                viewshed.visible_tiles.clear();
+                viewshed.visible_tiles =
+                    field_of_view(Point::new(pos.x, pos.y), viewshed.range, &*map);
+                viewshed
+                    .visible_tiles
+                    .retain(|p| p.x > 0 && p.x < map.width - 1 && p.y > 0 && p.y < map.height - 1);
+                viewshed.dirty = false;
 
-            // If this is the player, reveal what they can see
-            let p: Option<&Player> = player.get(ent);
-            if let Some(_) = p {
-                for t in map.visible_tiles.iter_mut() {
-                    *t = false
-                }
-                for vis in viewshed.visible_tiles.iter() {
-                    let idx = map.xy_idx(vis.x, vis.y);
-                    map.revealed_tiles[idx] = true;
-                    map.visible_tiles[idx] = true;
+                // If this is the player, reveal what they can see
+                let p: Option<&Player> = player.get(ent);
+                if let Some(_) = p {
+                    for t in map.visible_tiles.iter_mut() {
+                        *t = false
+                    }
+                    for vis in viewshed.visible_tiles.iter() {
+                        let idx = map.xy_idx(vis.x, vis.y);
+                        map.revealed_tiles[idx] = true;
+                        map.visible_tiles[idx] = true;
+                    }
                 }
             }
         }