The best way to 'deactivate'/'activate' various objects?

[Volnaiskra]

Hi, I'd like to make a level where a select few elements of various types (eg. ledges, enemies, doors) are 'greyed out' until you activate them. They'd be faintly visible, and would behave as normal, but the player would not be able to interact with them (would fall through ledges, enemies would not harm him, doors wouldn't open, etc.) , and would be able to walk through them. Once a certain switch in the level had been activated, these elements would become solid, and would behave just like their normal counterparts.

Ideally, I'd like to be able to just add a single attribute to those elements which are to be greyed out, so that I can control them simply from one place. In other words, I'd like to be able to turn things on and off in the code.

I first thought that I could achieve this by giving the greyed out elements a qualifier (eg. "neutral"), and then changing that qualifier when it's time to un-grey them (eg. "good"). But it doesn't seem you can change qualifiers on the fly.

Then, I thought that I could make all greyed out objects have a high translucency, and test for an element's alpha transparency. For example, on my collision code, I'd say "if object has alpha value < 80, then do collisions", which would ignore all the greyed out objects (which would have an alpha of, say, 200). But it doesn't seem that you can test for alpha.

I can't just use "make visible/invisible", because I need these elements to be faintly visible. Also, "invisible" elements still behave as normal (ie. invisible enemies still hurt you).

What would the best way be to achieve this? I'd really love to be able to just somehow 'switch' certain elements on and off, without having to put "if, then" statements across all of my code, as that seems like it would add a lot of cpu overhead.

Thanks in advance

[BartekB]

You can use a flag to toggle them off and on.
In the new condition, you just put if flag is on or off and an event.
You can find flags in the alterable values section in new conditions window and in flags in the drop down object menu.
EDIT: If you don't want to have "If flag is on then bluh" on all the code that has to do with the object. Simply move them to another layer so the both objects don't collide.

[Ls2]

You can put all the actions and events inside a group. So, when you activate this group, the objects will turn on. Also, you may create two groups, one with the events related to the behavior "off" and the another with the behavior of "on" state.

[Volnaiskra]

EDIT: If you don't want to have "If flag is on then bluh" on all the code that has to do with the object. Simply move them to another layer so the both objects don't collide.

Brilliant. I think this is what I was looking for. A simple, clever way to deactivate anything without having to hardcode anything beforehand.

Thanks guys.