In the progress, i already did some optimization through designing this level. I add some “AreaPortal” (name identical from source hammer editor) but use manual scripting  to disable part of the level from being draw at once. This will increase performance in FPS (hopefully). The drawback is the stutter (probably from low phone RAM?) when to enable new complex map at front. Well not really noticeable in some part but i need to learn some more for optimization technique. Too bad, free version of Unity not support auto-LOD…. i’m sad.

By the way, here sneak peek of gameplay: