One time events.

[DelJaRoo]

Is there any good way to create things that only happen once?
More specificly, I am looking for a way to have a set of screens that once they're completed they cannot be revisited.
Thank you in advance.

[Joe123]

Yep, and it's not too difficult either. What version are you using though? In 2.10, and earlier, you need to use Boss Flags and Trigger enemies, while in later betas there's an easier way via Room State Carryovers.

[Rakshiba]

I have a suggestion but it might not help. When you enter a screen onto an un-walkable tile you have the ability to walk back to the last screen or walk to an walkable tile adjacent to Link's possition on the screen. By putting a non-destructable and un-walkable tile on the enterance to the screen immediatly after the area you want don't want the player to be able to return to, You can permanantly block that path...downsidea are though, obviously you can re-enter the area from the original enterance, and it looks odd if Link is suddenly standing on a tree. Of course doing with the proper layering you can make it as if Link were comming through the tree as if it was a forest.

[DelJaRoo]

I'm using 2.10 (I didn't know there were newer betas.) Would it better to start using one of the betas?
Either way, I would love to learn both methods.

[Joe123]

Well, if you're sticking on 2.10 there's no need to learn the new methods (because they aren't in it :p). I personally haven't really made anything on any newer betas - partially because I don't know how many of the new features work, and also because I'd like to finish projects I've started on 2.10.

So, to make an event happen only once, you must either trigger something to happen on a different screen to the one you are on - or use a whole new duplicate area - or a combination of both.

To make something trigger on a different screen in 2.10, you must have both of the screens on a Dmap with the same level number. You assign both of the screens the 'Dungeon Boss' enemy flag (which you access by pressing F12 on that screen). On the screen you want the secret to be trigger on, you must make the only enemy be a 'trigger' enemy, and also set the screen flags 'Enemies -> Secret' and probably 'No Secret Sounds'.
Once you have set it up like that, when you kill an enemy set on the other screen, it will trigger any secrets set down on that screen (via flags 16-32).

Then you put an enemy on the other screen, and viola, you can change something on a different screen to the one you are on.

Which is fine, but not all that helpful unless you know how to use it.
So say you have a screen in a dungeon with a guy that says one string before you beat the boss - and a different one after.
The way you'd do this is to have the first string set up as normal - then to make him say the second string you'd have to make a duplicate screen - where everything looked the same, except he said a different string. To make him say this string, in the room before you enter the guy's room you'd have the trigger set up as I explained earlier. Then you'd have flag 16 revealing two stair combos in the doorway (although they'd be disguised as the normal doorway combos so the player didn't know), then you'd have the tilewarp from that screen take you to the duplicate screen - rather than the original one - with the second string.

So when the player plays through the level, the first time of entering the room the guy says the first string. Then, on beating the boss, the trigger is activated, and the secret flags are changed to stair combos. Then, when the player walks to the room with the guy saying the string, instead of walking into that room, the stair combos take him to the duplicate room with the new string.

You need a reasonable knowledge of ZC for that though (and I have no idea of how well you understand it). If you don't understand anything, I'll try to explain better.

[DelJaRoo]

Wow, that's a neat little trick! I totally understand.
Much appreciation, that is very helpful.

[lupinealchemist]

How about when you want to make the boss say something when you defeat it?
Do I set the screen flag "enemies>secret" then place flag 16 all over the screen with the secret tile being a direct warp, will that work?

[Joe123]

If the direct warp takes you to a duplicate room with the boss saying a string, that will indeed work. Also, if you don't want to make duplicate combos of all of the floor tiles which are 'direct warp', you could make the floor of the room on layer 1.