Took a look, a few suggestions :
- To give your map a name in the loading screen, enter a "message" field into any worldspawn.
- Your walls are too thin. As a general rule, I usually go with at least 16 gu for wall thickness, just because walls look silly when they are paper-thin.
- The vents are kind of pointless. They lead straight into the slime, which is useless, and they are so long even a blaster could hold aliens off. THeyt should be filled with slime anyways, if physics meant anything

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-The rotating fan thing is fairly pointless as well. Does it even have a purpose? If you want to keep it, you should make it so that it is supported by something, and not just floating there.
- Rants can't get to the cannons, or even fit in them, which is probably a good idea to make possible for a silly map like this.
- What's up with the doors? Specs cant float through them. Why not just use func_door?
- Make your bridge a little sturdier. Thicker, and supported.
- Make the map less of an MD haven. Add some obstacles, things to hide behind, etc, etc.
- The little platforms way up in the corners are stupid. A human base up there would be chaos, and would probably ruin a game.
- I'm guessing it's not permanent, but you should always start humans and aliens with a reactor/om, and usually a turret/tube or two at least.
All in all, a lot of newbie mistakes, but hopefully you will learn and make this a fun an interesting map

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