Optimization using Allegro in C++

What's up /prog/,
I'm currently trying to write an rts/ shooter using C++ and allegro. By shooter/rts, I mean shooter in the terms of ikuraga, and rts in that you will be switching control of units as well as being able to "freeze" the area around the ship you are currently controlling and que some command for the flotilla you are commanding.
Seeing as I have this in mind, I need to be able to have at least 90 units in the game without visible slowdown, so if you have some suggestions, I'm open to anything.

Thanks!

Reasonably fast collision detection algorithm:
http://www.shmup-dev.com/forum/index.php?action=printpage;topic=1636.0

Also note that only fixed frame rate is acceptable in shooting games, which means you'll have to use the graphics card as the timing source (vsync).  Please support both 60Hz and 120Hz for future compatibility, as people can't keep ignoring the obvious advantages of 120Hz displays forever.

I also recommend making your game deterministic, for easy replay saving/playback.

What's your Ikaruga score?  How many other shooting games have you 1CCed?  If you can't play these games well then you have no chance of making a good one.  But if this is just a learning exercise then don't worry about it.

>>22
http://www.gamasutra.com/view/feature/3057/instant_replay_building_a_game_.php?print=1