So i want to protect my game with copyright how can i do?

As long as you don't mean to harm anyone with your copyright, I'm okay.

Why???
You are using an free, open source, programming environment where your code is not protected from prying eyes.
(If I play a game and find a feature I like, I am not above checking out how it is done and if I can use the idea in my game.)
If you are going to create something worth copyrighting, you would need to program everything from the ground up with a programming language, compile it to protect the code, then get a lawyer and spend the money to verify that your idea is not a copy of someone else's and that it truly is an original idea...
and so on... and so on...
Get the idea?

I think Darklizerd was trying to say "programming environment where your code is protected from prying eyes."

You can always just publish it and have it unlisted. That option is always recommended for programmers who need their code looked at by others but it isn't finished enough to publish it. Also, the website has a problem with too many games in the sandpit category.

I actually talked to a girl about this. I told her she could publish it unlisted, but if she published it for real, it would be public to everyone. She ended up going to a different site.

I agree with DarkLizerd that copy-righting is a lot of work. You don't need to start your game over, but you will have to edit the game, register for a patent, wait, pay money, and then wait more.
And that's just a basic idea. I don't know the specifics.

Oh, and under U.S. law, if you want to keep the copy-right, say 5 years, you will need to "use it" in court. You can file a suit against yourself... I don't know how that works.
Not that most people need a copy-right for 1 year anyway, let alone 5 years...

I thought anything written by me had a copyright by default?

https://www.copyright.gov/help/faq/faq-general.html#mywork

(Leo is in Italy, though. I couldn't find that page online.)

...but...

Quest is definitely open source, and your game's code is easily accessible.

Even if the game was compiled to something human's couldn't read, someone would just release a decompiler. (They have many to choose from if you want to get into an INFOCOM game's code, and the same decompiler works on Inform games.)

I've heard of people compiling their own games, but, the fact is, the text still prints to the screen. It's not that hard to learn how to make a text adventure (especially if you have the text and know what should happen)...

It's virtually impossible to keep your code 'secret'.

Found Italy's:

https://en.wikipedia.org/wiki/Copyright_law_of_Italy#Ownership

This all concerns written work, by the way.

I don't know how using Quest may effect anything.

Hey, look...

It says it on the Submit page

http://textadventures.co.uk/submit/submitfile

By uploading a game here, you agree to the following:

• you are the author of this game, or have the author's permission to upload it for them
• if there is any copyrighted material in the game, you have permission to use it
• we can distribute this game on textadventures.co.uk and activelit.com

In return, we promise:

• you keep all the copyright in the game
• we will use your submission solely to make it available on our websites, and always freely
• we will never sell or modify your game
• you'll always be credited as the author

I am no expert, but my understanding is:

Any creative article you create you automatically have copyright. I think computer code is quite a stretch for copyright, but there is huge precedent. However, something like a text adventure will be covered, as it is clearly creative.

If it comes to court... It will help if you assert the copyright somewhere in your game ("copyright ITSLEO 2017", with the credits or under the title; maybe best to use your real name) and if you have some way to prove its date of release (the upload date on the web site might be good enough, but if you have a lawyer friend, e-mailing it to him or her might help too).

On the other hand, if you are really asking how you can physically stop people copying your game or looking at the source code, then really there is no way.

Could you be looking for copy protection to protect your code from being looked at and duplicated???
The problem with code is that it is a lot like human languages...
You can't copy right "This is a test" and prevent anyone else from saying it...
But, you can copyright your game if it can be proven to be truly original.
This would prevent someone from creating something that is almost identical...
(Side note, as I heard the story...)
A writer proposed a script to Hollywood, maybe even to (the Star Trek producers) about a space station series, but it was turned down... Star Trek is about a spaceship going TO the adventure, no waiting for the adventure to come to it...
Later, Babylon 5 was on TV...
(I think it was later) Star Trek, DS 9 aired...
There were claims of copy write infringement there...
Different stories, but the could both be from the same idea... The question would be, "Who was first with the idea?"

So, back to the original question... Are you doing this for fun??? or do you plan on making millions of dollars??? That should tell you if you need to even worry about copyrights...

Actually DS9 aired before B5, but yes the creator of B5 had gone to the Star Trek previously, been refused. They just managed to get DS9 out faster. But your cannot copyright an idea, only the creative work itself.

Both were good shows...
just couldn't remember which one I saw first.

Ants vs. a Bugs' Life... no wait, I need a better example....

This one company vs. all pixel shooters in space. I don't know. I saw a story about it on YouTube. Space invaders (I think) thought they should be the only shooting game in space, but the court turned down the claim, saying space shooters is an idea, not a trademark.

I'm just replying to the current conversation now.