diff --git a/My_settings.h b/My_settings.h
index 2f01c4c..e32ed85 100644
--- a/My_settings.h
+++ b/My_settings.h
@@ -1,3 +1,4 @@
+#define SPEED_MULTIPLIER 1
 #define PROJ_SHOW_FPS_COUNTER
 #define PROJ_SCREENMODE 13
 #define PROJ_MODE13 1
diff --git a/demo1.cpp b/demo1.cpp
index db365a0..f2bb66f 100644
--- a/demo1.cpp
+++ b/demo1.cpp
@@ -21,8 +21,9 @@
 
 // redefine some parameters
 #define FPS 255
-#define GRAVITY_ACCELERATION (RCL_UNITS_PER_SQUARE * 3)
-#define PLAYER_JUMP_SPEED 700
+#define PLAYER_SPEED (RCL_UNITS_PER_SQUARE * 2 * SPEED_MULTIPLIER)
+#define GRAVITY_ACCELERATION (RCL_UNITS_PER_SQUARE * SPEED_MULTIPLIER)
+#define PLAYER_JUMP_SPEED 400
 #define RCL_CAMERA_COLL_HEIGHT_BELOW ((3 * RCL_UNITS_PER_SQUARE) / 2)
 #define RCL_HORIZONTAL_FOV (RCL_UNITS_PER_SQUARE / 5)
 
@@ -1284,8 +1285,8 @@ int main()
           moveDirection = -1;
       }
 
-      player.update(moveDirection,strafe,rotationDirection,pokitto.bBtn(),shearDirection,
-        floorHeightAt,ceilingHeightAt,true,dt);
+      player.update(moveDirection,strafe,rotationDirection,pokitto.bBtn(),
+        shearDirection,floorHeightAt,ceilingHeightAt,true,dt);
     }
   }
 
diff --git a/demo2.cpp b/demo2.cpp
index d953eee..448d526 100644
--- a/demo2.cpp
+++ b/demo2.cpp
@@ -73,7 +73,7 @@
 #define FPS 255
 #define HEAD_BOB_HEIGHT 200
 #define HEAD_BOB_STEP 20
-#define PLAYER_SPEED (5 * RCL_UNITS_PER_SQUARE)
+#define PLAYER_SPEED (4 * RCL_UNITS_PER_SQUARE * SPEED_MULTIPLIER)
 
 #define TEXTURE_W 32 // for the sake of performance we require prespecified sizes
 #define TEXTURE_H 32
diff --git a/demo3.cpp b/demo3.cpp
index 5ab609c..6790e0b 100644
--- a/demo3.cpp
+++ b/demo3.cpp
@@ -13,9 +13,10 @@
 #define SUBSAMPLE 1
 
 // redefine player's height
-#define PLAYER_SPEED (RCL_UNITS_PER_SQUARE * 6)
+#define PLAYER_SPEED (RCL_UNITS_PER_SQUARE * 4 * SPEED_MULTIPLIER)
+#define PLAYER_JUMP_SPEED 600
 #define RCL_HORIZONTAL_FOV ((3 * RCL_UNITS_PER_SQUARE) / 10)
-#define GRAVITY_ACCELERATION (RCL_UNITS_PER_SQUARE * 2)
+#define GRAVITY_ACCELERATION (RCL_UNITS_PER_SQUARE * 2 * SPEED_MULTIPLIER)
 #define RCL_CAMERA_COLL_HEIGHT_BELOW ((3 * RCL_UNITS_PER_SQUARE) / 2)
 #define FPS 255
 #define HEAD_BOB_HEIGHT 150