diff --git a/squirrelbattle/display/mapdisplay.py b/squirrelbattle/display/mapdisplay.py
index 54d9432..c4f29e3 100644
--- a/squirrelbattle/display/mapdisplay.py
+++ b/squirrelbattle/display/mapdisplay.py
@@ -15,8 +15,15 @@ class MapDisplay(Display):
         self.pad = self.newpad(m.height, self.pack.tile_width * m.width + 1)
 
     def update_pad(self) -> None:
-        self.addstr(self.pad, 0, 0, self.map.draw_string(self.pack),
-                    self.pack.tile_fg_color, self.pack.tile_bg_color)
+        for j in range(len(self.map.tiles)):
+            for i in range(len(self.map.tiles[j])):
+                color = self.pack.tile_fg_visible_color if \
+                    self.map.visibility[j][i] else self.pack.tile_fg_color
+                self.addstr(self.pad, j, self.pack.tile_width * i,
+                            self.map.tiles[j][i].char(self.pack),
+                            color, self.pack.tile_bg_color)
+        # self.addstr(self.pad, 0, 0, self.map.draw_string(self.pack),
+        #             self.pack.tile_fg_color, self.pack.tile_bg_color)
         for e in self.map.entities:
             self.addstr(self.pad, e.y, self.pack.tile_width * e.x,
                         self.pack[e.name.upper()],
diff --git a/squirrelbattle/display/texturepack.py b/squirrelbattle/display/texturepack.py
index f72cd97..fb56dd5 100644
--- a/squirrelbattle/display/texturepack.py
+++ b/squirrelbattle/display/texturepack.py
@@ -2,7 +2,7 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 
 import curses
-from typing import Any
+from typing import Any, Union, Tuple
 
 
 class TexturePack:
@@ -10,10 +10,11 @@ class TexturePack:
 
     name: str
     tile_width: int
-    tile_fg_color: int
-    tile_bg_color: int
-    entity_fg_color: int
-    entity_bg_color: int
+    tile_fg_color: Union[int, Tuple[int, int, int]]
+    tile_fg_visible_color: Union[int, Tuple[int, int, int]]
+    tile_bg_color: Union[int, Tuple[int, int, int]]
+    entity_fg_color: Union[int, Tuple[int, int, int]]
+    entity_bg_color: Union[int, Tuple[int, int, int]]
 
     BODY_SNATCH_POTION: str
     BOMB: str
@@ -54,9 +55,10 @@ class TexturePack:
 TexturePack.ASCII_PACK = TexturePack(
     name="ascii",
     tile_width=1,
+    tile_fg_visible_color=(1000, 1000, 1000),
     tile_fg_color=curses.COLOR_WHITE,
     tile_bg_color=curses.COLOR_BLACK,
-    entity_fg_color=curses.COLOR_WHITE,
+    entity_fg_color=(1000, 1000, 1000),
     entity_bg_color=curses.COLOR_BLACK,
 
     BODY_SNATCH_POTION='S',
@@ -80,10 +82,11 @@ TexturePack.ASCII_PACK = TexturePack(
 TexturePack.SQUIRREL_PACK = TexturePack(
     name="squirrel",
     tile_width=2,
+    tile_fg_visible_color=(1000, 1000, 1000),
     tile_fg_color=curses.COLOR_WHITE,
     tile_bg_color=curses.COLOR_BLACK,
-    entity_fg_color=curses.COLOR_WHITE,
-    entity_bg_color=curses.COLOR_WHITE,
+    entity_fg_color=(1000, 1000, 1000),
+    entity_bg_color=(1000, 1000, 1000),
 
     BODY_SNATCH_POTION='🔀',
     BOMB='💣',
diff --git a/squirrelbattle/entities/player.py b/squirrelbattle/entities/player.py
index 19c8348..6d18884 100644
--- a/squirrelbattle/entities/player.py
+++ b/squirrelbattle/entities/player.py
@@ -21,7 +21,7 @@ class Player(InventoryHolder, FightingEntity):
                  strength: int = 5, intelligence: int = 1, charisma: int = 1,
                  dexterity: int = 1, constitution: int = 1, level: int = 1,
                  current_xp: int = 0, max_xp: int = 10, inventory: list = None,
-                 hazel: int = 42, *args, **kwargs) \
+                 hazel: int = 42, vision: int = 5, *args, **kwargs) \
             -> None:
         super().__init__(name=name, maxhealth=maxhealth, strength=strength,
                          intelligence=intelligence, charisma=charisma,
@@ -32,6 +32,7 @@ class Player(InventoryHolder, FightingEntity):
         self.inventory = self.translate_inventory(inventory or [])
         self.paths = dict()
         self.hazel = hazel
+        self.vision = vision
 
     def move(self, y: int, x: int) -> None:
         """
@@ -42,6 +43,7 @@ class Player(InventoryHolder, FightingEntity):
         self.map.currenty = y
         self.map.currentx = x
         self.recalculate_paths()
+        self.map.compute_visibility(self.y, self.x, self.vision)
 
     def level_up(self) -> None:
         """
diff --git a/squirrelbattle/interfaces.py b/squirrelbattle/interfaces.py
index 6458df7..89399f5 100644
--- a/squirrelbattle/interfaces.py
+++ b/squirrelbattle/interfaces.py
@@ -4,7 +4,8 @@
 from enum import Enum, auto
 from math import sqrt
 from random import choice, randint
-from typing import List, Optional, Union, Tuple, Any
+from typing import List, Optional, Tuple, Any
+from math import ceil
 
 from .display.texturepack import TexturePack
 from .translations import gettext as _
@@ -38,19 +39,25 @@ class Slope():
         self.Y = y
         self.X = x
 
-    def compare(self, other: Union[Tuple[int, int], "Slope"]) -> int:
-        if isinstance(other, Slope):
-            y, x = other.Y, other.X
-        else:
-            y, x = other
+    def compare(self, other: "Slope") -> int:
+        y, x = other.Y, other.X
         return self.Y * x - self.X * y
 
-    def __lt__(self, other: Union[Tuple[int, int], "Slope"]) -> bool:
+    def __lt__(self, other: "Slope") -> bool:
         return self.compare(other) < 0
 
-    def __eq__(self, other: Union[Tuple[int, int], "Slope"]) -> bool:
+    def __eq__(self, other: "Slope") -> bool:
         return self.compare(other) == 0
 
+    def __gt__(self, other: "Slope") -> bool:
+        return self.compare(other) > 0
+
+    def __le__(self, other: "Slope") -> bool:
+        return self.compare(other) <= 0
+
+    def __ge__(self, other: "Slope") -> bool:
+        return self.compare(other) >= 0
+
 
 class Map:
     """
@@ -194,16 +201,16 @@ class Map:
         if top.X == 1:
             top_y = x
         else:
-            top_y = ((x * 2 - 1) * top.Y + top.X) / (top.X * 2)
+            top_y = ceil(((x * 2 - 1) * top.Y + top.X) / (top.X * 2))
             if self.is_wall(top_y, x, octant, origin):
-                if top >= (top_y * 2 + 1, x * 2) and not\
+                if top >= Slope(top_y * 2 + 1, x * 2) and not\
                         self.is_wall(top_y + 1, x, octant, origin):
                     top_y += 1
             else:
                 ax = x * 2
                 if self.is_wall(top_y + 1, x + 1, octant, origin):
                     ax += 1
-                if top > (top_y * 2 + 1, ax):
+                if top > Slope(top_y * 2 + 1, ax):
                     top_y += 1
         return top_y
 
@@ -212,9 +219,9 @@ class Map:
         if bottom.Y == 0:
             bottom_y = 0
         else:
-            bottom_y = ((x * 2 + 1) * bottom.Y + bottom.X) /\
-                (bottom.X * 2)
-            if bottom >= (bottom_y * 2 + 1, x * 2) and\
+            bottom_y = ceil(((x * 2 - 1) * bottom.Y + bottom.X)
+                            / (bottom.X * 2))
+            if bottom >= Slope(bottom_y * 2 + 1, x * 2) and\
                     self.is_wall(bottom_y, x, octant, origin) and\
                     not self.is_wall(bottom_y + 1, x, octant, origin):
                 bottom_y += 1
@@ -223,17 +230,18 @@ class Map:
     def compute_visibility_octant(self, octant: int, origin: Tuple[int, int],
                                   max_range: int, distance: int, top: Slope,
                                   bottom: Slope) -> None:
-        for x in range(distance, max_range):
+        for x in range(distance, max_range + 1):
             top_y = self.crop_top_visibility(octant, origin, x, top)
             bottom_y = self.crop_bottom_visibility(octant, origin, x, bottom)
             was_opaque = -1
             for y in range(top_y, bottom_y - 1, -1):
-                if sqrt(x**2 + y**2) > max_range:
+                if x + y > max_range:
                     continue
                 is_opaque = self.is_wall(y, x, octant, origin)
                 is_visible = is_opaque\
-                    or ((y != top_y or top > (y * 4 - 1, x * 4 - 1))
-                        and (y != bottom_y or bottom < (y * 4 + 1, x * 4 + 1)))
+                    or ((y != top_y or top > Slope(y * 4 - 1, x * 4 + 1))
+                        and (y != bottom_y
+                             or bottom < Slope(y * 4 + 1, x * 4 - 1)))
                 if is_visible:
                     self.set_visible(y, x, octant, origin)
                 if x == max_range:
@@ -242,7 +250,7 @@ class Map:
                     nx, ny = x * 2, y * 2 + 1
                     if self.is_wall(y + 1, x, octant, origin):
                         nx -= 1
-                    if top > (ny, nx):
+                    if top > Slope(ny, nx):
                         if y == bottom_y:
                             bottom = Slope(ny, nx)
                             break
@@ -257,8 +265,9 @@ class Map:
                     nx, ny = x * 2, y * 2 + 1
                     if self.is_wall(y + 1, x + 1, octant, origin):
                         nx += 1
-                    if bottom >= (ny, nx):
+                    if bottom >= Slope(ny, nx):
                         return
+                    top = Slope(ny, nx)
                 was_opaque = is_opaque
             if was_opaque != 0:
                 break
@@ -268,31 +277,33 @@ class Map:
                         origin: Tuple[int, int]) -> Tuple[int, int]:
         ny, nx = origin
         if octant == 0:
-            return nx + x, ny - y
+            return ny - y, nx + x
         elif octant == 1:
-            return nx + y, ny - x
+            return ny - x, nx + y
         elif octant == 2:
-            return nx - y, ny - x
+            return ny - x, nx - y
         elif octant == 3:
-            return nx - x, ny - y
+            return ny - y, nx - x
         elif octant == 4:
-            return nx - x, ny + y
+            return ny + y, nx - x
         elif octant == 5:
-            return nx - y, ny + x
+            return ny + x, nx - y
         elif octant == 6:
-            return nx + y, ny + x
+            return ny + x, nx + y
         elif octant == 7:
-            return nx + x, ny + y
+            return ny + y, nx + x
 
     def is_wall(self, y: int, x: int, octant: int,
                 origin: Tuple[int, int]) -> bool:
         y, x = self.translate_coord(y, x, octant, origin)
-        return self.tiles[y][x].is_wall()
+        return 0 <= y < len(self.tiles) and 0 <= x < len(self.tiles[0]) and \
+            self.tiles[y][x].is_wall()
 
     def set_visible(self, y: int, x: int, octant: int,
                     origin: Tuple[int, int]) -> None:
         y, x = self.translate_coord(y, x, octant, origin)
-        self.visibility[y][x] = True
+        if 0 <= y < len(self.tiles) and 0 <= x < len(self.tiles[0]):
+            self.visibility[y][x] = True
 
     def tick(self) -> None:
         """