While exploring developing games, especially 3d games, i figured out the FPSCreator.
If you ask whats Fps, thats a gaming type, and if i say "Counter Strike", im sure u all will get it.
You can use floor-segments-,characters, furnitures, items, guns, wall, stairs,monsters...lol..everything..
and believe me, its never been easir!
btw, im not an adviser of that program
but, it deserves..
note : the program is not freeware.
note : the program has some bugs. in my first time, i did a game with 4floors.while building it -to .exe- it showed me a Error 0:0 ...
ERROR 0:0, the program's worst error..but, error 0:0 means there is no error actually..
anyway..
u should try it really..
www.fpscreator.com
bye.


