fp: Use meters for calculations

feely_pona_game.h

@@ -97,7 +97,9 @@ struct FP_GameEntity
     Dqn_String8                           name;
     FP_GameEntityHandle                   handle;
 
-    Dqn_V2                                size_scale;
+    // The target size to render the sprite in meters. The width of the sprite
+    // is scaled uniformly with respect to the height.
+    FP_Meters                             sprite_height;
     FP_GameEntityAction                   action;
     Dqn_V2                                velocity;
 
@@ -175,6 +177,7 @@ struct FP_Game
     FP_GameCamera                         camera;
     TELY_RFui                             rfui;
 
+    Dqn_f32                               meters_to_pixels;
     uint64_t                              clock_ms;
 };