In total about four months. Things that took us most of the time were writing shaders and balancing towers. Actually, we used much less shaders than we did.
wow you did a tremendous job in such a short time. How big is your team??

[offtopic]
....and mp3 reproduction capability (to listen your favorite music ingame).....
I like to have such a feature in my engine too.
But the problem is:

I like to use one system/API for sound. I think OpenAL is a good choice, but the problem is that it doesn't support Mp3. I will have to decode mp3 myself, which is not allowed because mp3 is heavily pattented.

So How do you achieve this? Are you using seperate systems for Mp3 and soundeffects??
like e.g Bass for SFX and TMediaPlayer for MP3. Do you decode MP3 :twisted: Or is there another way??
[/offtopic]