diff --git a/src/map.rs b/src/map.rs
index 9e56083..1292c62 100644
--- a/src/map.rs
+++ b/src/map.rs
@@ -10,12 +10,13 @@ use crate::component::Viewshed;
 use crate::entity::{Player, TileType};
 use crate::rect::Rect;
 
-#[derive(Clone)]
+#[derive(Clone, Default)]
 pub struct Map {
     pub tiles: Vec<TileType>,
     pub rooms: Vec<Rect>,
     pub width: i32,
     pub height: i32,
+    pub revealed_tiles: Vec<bool>,
 }
 
 impl Algorithm2D for Map {
@@ -86,6 +87,7 @@ impl Map {
             rooms: vec![],
             width: 80,
             height: 50,
+            revealed_tiles: vec![false; 80 * 50],
         };
 
         const MAX_ROOMS: i32 = 30;
@@ -163,45 +165,38 @@ pub fn new_test() -> Vec<TileType> {
 */
 
 pub fn draw(ecs: &World, ctx: &mut Rltk) {
-    let mut viewsheds = ecs.write_storage::<Viewshed>();
-    let mut players = ecs.write_storage::<Player>();
     let map = ecs.fetch::<Map>();
+    let mut y = 0;
+    let mut x = 0;
 
-    (&mut players, &mut viewsheds).join().into_iter().for_each(
-        |(_player, viewshed)| {
-            let mut y = 0;
-            let mut x = 0;
-            map.tiles.iter().for_each(|tile| {
-                let pt = Point::new(x, y);
-                if viewshed.visible_tiles.contains(&pt) {
-                    match tile {
-                        TileType::Floor => {
-                            ctx.set(
-                                x,
-                                y,
-                                RGB::from_f32(0.5, 0.5, 0.5),
-                                RGB::from_f32(0., 0., 0.),
-                                rltk::to_cp437('.'),
-                            );
-                        }
-                        TileType::Wall => {
-                            ctx.set(
-                                x,
-                                y,
-                                RGB::from_f32(0.0, 1.0, 0.0),
-                                RGB::from_f32(0., 0., 0.),
-                                rltk::to_cp437('#'),
-                            );
-                        }
-                    }
+    map.tiles.iter().enumerate().for_each(|(idx, tile)| {
+        if map.revealed_tiles[idx] {
+            match tile {
+                TileType::Floor => {
+                    ctx.set(
+                        x,
+                        y,
+                        RGB::from_f32(0.5, 0.5, 0.5),
+                        RGB::from_f32(0., 0., 0.),
+                        rltk::to_cp437('.'),
+                    );
                 }
+                TileType::Wall => {
+                    ctx.set(
+                        x,
+                        y,
+                        RGB::from_f32(0.0, 1.0, 0.0),
+                        RGB::from_f32(0., 0., 0.),
+                        rltk::to_cp437('#'),
+                    );
+                }
+            }
+        }
 
-                x += 1;
-                if x > 79 {
-                    x = 0;
-                    y += 1;
-                }
-            });
-        },
-    );
+        x += 1;
+        if x > 79 {
+            x = 0;
+            y += 1;
+        }
+    });
 }
diff --git a/src/visibility.rs b/src/visibility.rs
index 19b053d..5d24eaa 100644
--- a/src/visibility.rs
+++ b/src/visibility.rs
@@ -1,4 +1,4 @@
-use super::{Map, Position, Viewshed};
+use super::{Map, Player, Position, Viewshed};
 use rltk::{field_of_view, Point};
 use specs::prelude::*;
 
@@ -6,22 +6,32 @@ pub struct VisibilitySystem {}
 
 impl<'a> System<'a> for VisibilitySystem {
     type SystemData = (
-        ReadExpect<'a, Map>,
+        WriteExpect<'a, Map>,
+        Entities<'a>,
         WriteStorage<'a, Viewshed>,
         WriteStorage<'a, Position>,
+        ReadStorage<'a, Player>,
     );
 
     fn run(&mut self, data: Self::SystemData) {
-        let (map, mut viewshed, pos) = data;
-        (&mut viewshed, &pos).join().into_iter().for_each(
-            |(viewshed, pos)| {
+        let (mut map, entities, mut viewshed, pos, player) = data;
+        (&entities, &mut viewshed, &pos)
+            .join()
+            .into_iter()
+            .for_each(|(ent, viewshed, pos)| {
                 viewshed.visible_tiles.clear();
                 viewshed.visible_tiles = field_of_view(
                     Point::new(pos.x, pos.y),
                     viewshed.range,
                     &*map,
                 );
-            },
-        );
+                let p: Option<&Player> = player.get(ent);
+                if let Some(p) = p {
+                    viewshed.visible_tiles.iter().for_each(|vis| {
+                        let idx = map.xy_idx(vis.x, vis.y);
+                        map.revealed_tiles[idx] = true;
+                    });
+                }
+            });
     }
 }