Warning Lights
I'm currently working on a map similar to The Flood, and I have an idea that I don't know how to implement.
See, everything is divided to puzzles with an incremented difficulty. Starting with very simple Box-Goes-Here puzzles, and working it's way to Fling-Yourself-across-this-giant-assed-gap-while-holding-down-5-buttons type puzzles, all with a large body of water slowly rising over the map.
What I want to do, since it's so hard to see where the water is, have warning lights in the corner of each room, like 3 normal lights that go off as the water comes up and then a big red siren-light thing that lights up when you're about to die. I have no idea how to do this, though. Any suggestions?
just make those lights / ambients delayed so it matches the water levels.
and the water as a func door.
u could also make a GLaDOs voice that notices about the water levels.
dunno if i answered ur question. but u could make triggers at all accesiable areas so that ur warnings matches the players position and water levels
Do you have ANY idea how long it would take to get that exact?
What I was thinking of was a type of button that is switched on when the water touches it, outside of the map, and that corresponds with a light.
very long.
Why can't you have a sort of mist above the fluid surface? So that if the water rises, you first see the clouds, which makes you think: 'shouldn't I make a move on?'
apart from that.
I also had in mind this kind of map, but then it would be one tall chamber, where you climb up quickly via lots of obstacles, puzzles and other stuff to avoid being swallowed by the goo.
Why can't you have a sort of mist above the fluid surface? So that if the water rises, you first see the clouds, which makes you think: 'shouldn't I make a move on?'
I woudl do that, but dustclouds lag my computer to shit.
then I got two solutions to your problem!
1. Get a new PC (recommended) 
2. make no dustclouds, but fog.
1. Get a new PC (recommended)
2. make no dustclouds, but fog.
1. I'm poor.
2. How would I make area specific fog?
I have no idea...
Quake 3 Arena editor could.
I'm not sure I understand exactly what you are trying to do. Are you saying thet you want a series of 4 lights, that activate based on how far above the water you are?
If so, you could position 4 trigger brushes at varying heights above the water surface, and parent them to the water so they rise with it. Then use these to activate the lights etc. as they reach the player
If I am misunderstanding your idea, can you be a bit more specific?