diff --git a/lib/constants.rb b/lib/constants.rb
index 5930462..13342df 100644
--- a/lib/constants.rb
+++ b/lib/constants.rb
@@ -10,7 +10,7 @@ class IMICFPS
   MODEL_METER_SCALE = 1.0
 
   # Earth
-  GRAVITY = 9.8 # m/s
+  EARTH_GRAVITY = 9.8 # m/s
   # Moon
-  # GRAVITY = 1.625 # m/s
+  MOON_GRAVITY = 1.625 # m/s
 end
\ No newline at end of file
diff --git a/lib/managers/physics_manager.rb b/lib/managers/physics_manager.rb
index ada9330..671783b 100644
--- a/lib/managers/physics_manager.rb
+++ b/lib/managers/physics_manager.rb
@@ -31,7 +31,7 @@ class IMICFPS
         if on_ground
           entity.velocity.y = 0
         else
-          entity.velocity.y -= IMICFPS::GRAVITY * entity.delta_time if entity.physics
+          entity.velocity.y -= @collision_manager.map.gravity * entity.delta_time if entity.physics
         end
       end
     end
diff --git a/lib/map.rb b/lib/map.rb
index 0eaf66f..ae976b8 100644
--- a/lib/map.rb
+++ b/lib/map.rb
@@ -5,7 +5,7 @@ class IMICFPS
 
     attr_reader :collision_manager
     attr_reader :gravity
-    def initialize(map_loader:, gravity: IMICFPS::GRAVITY)
+    def initialize(map_loader:, gravity: IMICFPS::EARTH_GRAVITY)
       @map_loader = map_loader
       @gravity = gravity