Quote:

It's not about the length of the game that needs time. It's the complexity.



It depends on you!
Make a difference between demo and prototype!
Your prototype has to show whether the core of your game's gameplay and characters works and is fun to play!
And that can still be much less than the whole feature list!
It should be much less, otherwise the prototyping is not enough of a timeserver!

And then, even if you already have the whole featurelist working, when you build your levels, you will still find a lot of issues that you didn't expect, because of the levelgeometry itself, collision detection related and related to fps.
But, this is hopefully a smaller problem, if you reduce the levelgeometry from the beginning, like restricting it to certain heights of borders and ceilings, reduce it to certain width of dungeons, certain measures of the level as a whole, certain angles of edges of the levelgeometry, certain view distances...

http://www.puppenheim.org/
http://www.wuerfels-welt.de
Old Game Tutorial: http://www.puppenheim.org/MITutorial.zip
Free Game Editor: http://puppenheim.org/AlienalsWeihnachtsmann.zip
http://www.puppenheim.org/blender_starting_main_settings.txt