Unity APK size is too big for building the same scene

Question

I'm developing a game that should have 15-60 levels when all the environments of the levels are the same. I created a scene (level 1) and tried to build it; the total APK is around 38MB which is fine. But When I duplicated this scene to create the other levels and build my game the file size jumps to 148MB which is problematic for me.

Things I tried:

• I optimized meshes, textures, and audio files.
• I tried toggling static batching, SRP batching, GPU Instancing.

Here's some of the editor log of the second build:

Build Report
Uncompressed usage by category (Percentages based on user generated assets only):
Textures               6.2 mb    1.8% 
Meshes                 3.1 mb    0.9% 
Animations             781.3 kb  0.2% 
Sounds                 0.0 kb    0.0% 
Shaders                1.8 mb    0.5% 
Other Assets           652.6 kb  0.2% 
Levels                 323.1 mb  91.6% 
Scripts                3.6 mb    1.0% 
Included DLLs          13.4 mb   3.8% 
File headers           105.1 kb  0.0% 
Total User Assets      352.8 mb  100.0% 
Complete build size    678.6 mb
Used Assets and files from the Resources folder, sorted by uncompressed size:
 2.2 mb  0.3% Assets/Polygon/PolygonSamurai/Models/Characters.fbx
 1.2 mb  0.2% Packages/com.unity.render-pipelines.universal/Shaders/PostProcessing/UberPost.shader
 1.0 mb  0.2% Assets/TextMesh Pro/Resources/Fonts & Materials/LiberationSans SDF.asset

I'm sure I'm doing something wrong but I don't know where the main problem is. Any help is so appreciated.

Answer 1

I solved this by doing the following:

• I placed everything in one scene
• I created a prefab of every environment
• I created a game object for each level, initially turned off
• I created a script that loads a certain level and turns on/off the corresponding level objects and environment.

With this, my game composed of 15 levels dropped from 440Mb to only 45Mb.

Note: I used GPU instancing for the materials and turned off static batching for all elements, especially trees.