z    x
    | /
y __|/
   
z is up, looking at x  
theta = rotation along local z (rotate left/right)
phi = rotation along local y (look up/down) 

all path in files are relative to exe for now

intro file is static


====================================================
things to save in file
  default camera mode (M)
  speed
  angle


===================================================
key            |
   * done      |
   o not done  |
   - sorta done|
_______________.

control:
*  read input file (where do we put camera mode setting)
    general and control keys can be shared but not recommended
    camera/player control keys can be shared, switch with toggle
*  player/camera control toggle 
*  camera behavior toggle       
*    attached camera           
*    detached camera           
-    tailing camera
o   support multiple player
o   enable dynamic distance
o   collision detection
o   action: dialog

world:
  read course file
  skybox
  terrain
  model loading
  frustum culling
  collision detection
  character animation
  NPC AI

game:
  read game, intro file
  intro loop
  game loop : event triger
  message box : dialog, intro, input
  mini map: show/hide, show player

resource:
  make models
  find texture and images
  write story and dialog