pygame game 

sound files go to snd/ directory.
image files go to img/ directory.
Their names must be in this specific format(maybe add exception later to catch this).

"level number"_"file name".extension
level0_hello.mp3
level0_img1.png

find img and sound sources(credit)

stage directory holds stages(mini games).
Their names are in the format 'levelx', x being an integer.
This is no indication of difficulty of a level.
They must inherit from "class stage" and implement run(), next_level(), notify()

main.py is the main loop.
Manager.py is game manager: related to game loop, pause, quit
	      level mananger: a collection of level objects
	      resource manager: a collection of resources, images, sounds
	      event manager: send events to managers


Since you mentioned a stealthy game......
Make this a zombie game? Reason being because I like zombies.

Title : You need to learn to love zombies.

You play a zombie, and run from people.

People : 1) an ordinary liveling, they will call for help and bring more people
         2) a liveling with a bat, he/she will come for you and smash you
	 with a bat. One must get close to you though and they are only
	 slightly faster than you are. two-object near collision or collision.
	 3) a liveling with a gun, when he/she sees you, you are "dead".
	 when you get in his/her vision. we can make a gunner weaker or
	 stronger by limiting vision. may add hp points so you can take
	 more hits.

You : are a zombie. You try to walk away from livelings. You can run,
      but when you run, you leave a trail of your precious blood and meat
      behind which will trigger increase of caution level of livelings in
      area(decide how big).
      you can play dead(simply graphic of you lying down or make it fancier?).
      when you play dead, livelings will just walk by.
      when their caution level is high(playing dead after running for a period
      of time), gunner will shoot you.(decide the caution level threshold).

we make it tile game and design levels.
how about this?