Ok lets start with my Post to the Forums

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But first GO and buy the Rovio expansion pack. Its much simpler if you do this first.

Then Download the file attached to your N900. How you do this is upto you.

BUT DO NOT COPY THE FILE TO THE ROOT OF THE DEVICE.
ITS BEST COPIED INTO YOUR HOME DIRECTORY

untaring the file in the root of the device will take up valuable space and MAY CAUSE PROBLEMS

THEN ALL AS ROOT.

run
tar xzf custom-release.gz
cd custom

sh setup-cust-AB
this sets up AB to be custom level compatible.

sh run-cust
this allows you to play custom levels

sh run-rovio
changes back to rovio levels;

these 2 commands used to switch back and forth as you effectively swap the game between custom and official levels

sh reset
should be run before upgrading OS or buying rovio levels(i think) but is otherwise not needed
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Ok so the First bit would be simple if it didnt keep disappearing from the online shop. But i cant stress this enough Rovios beer great help, and very generous allowing me to tinker around.

SO onto the Install

FIrst a Warning. You should really try to understand what your doing if you tinker. I am not responsible for any trouble you get into. But i will try to help you if you do.
Saying that this is fairly simple and i will try explain whats happening.

You will need to have root access so see else where for that. And take REAL note of the Warning. Having root access is great but can be dangerous.

there really 2 options Dowload on a different machine and copy to phone or download from phone

either is as good as the other as long as you end up with the tarred file is on you phone and NOT (listen up folks) NOT in the root area. There whole threads about the problems filling the root area up

So /home/user
seems a good and sensible place.

Ok now you have a tarred and zipped file but thats not use to man nor mouse , so we need to unzip and untar

enter
tar xzf custom-release.gz
at the command line

This does as i suggested. it unzips (z option) and unpacks (x option ) . But google is you friend so go find out more about tar.

This should create a Directory called custom.
If i need to explain
cd custom

then you should give up now, and go do something less boring instead

now onto the clever bit
sh setup-cust-AB
this sets up AB to be custom level compatible.

sh runs a shell script. Shell is a basic programming language.

This checks if AB is running and moans if it is
It then moves all the Rovio files aside and copys my levels to the AB structure.
It then sets up symbolic links (go google again) that point to the Angry bird levels and level info

The 2 other scripts
sh run-cust
sh run-rovio effectively just move the symbolic links to point to rovio or custom levels

the final part
sh reset
should return the setup to how it was on AB install.
a sensible move before upgrading AB or the OS.

Hope this helps
Craig

I want to thank Craig for taking the time to explain, some of you might find some of his words “harsh” but to be honest, if you don’t understand and you are getting stuck, please google and/or ask for help, because the last thing we want is for you guess and then end up damaging your phone.

So To Summarise:

1. Extract Files (tar xzf custom-release.gz)
2. Go to your new custom folder (cd custom)
3. Setup Angrybirds to be custom level compatible (sh setup-cust-AB)
4. Play custom levels(sh run-cust)
5. Play normal levels(sh run-rovio)
6. Reset everything to the way it was in the beginning(sh reset)

Here is a link to the orginal post that Craig refers to:
http://talk.maemo.org/showpost.php?p=547863&postcount=148

Fear not my little friends because a few of us over at Maemo.org have started a thread for a Level editor. Another great thing is that @Miika over at Maemo.org is also an employee of Rovio and has been good enough to get us clearance to create our own levels and begin work on a level editor, head over and see how things are getting on.

I’ve also added a post to Maemo-freak here.
Quote from @Miika

First of all, wow! We anticipated requests for level editor but didn’t quite expect the users to put effort to reverse engineer their own. It’s very nice to see the level of interest Angry Birds has received from the Maemo community.
As for any possible legal issues no worries, go for it!

So while the level editor is being worked on, myself and @cgarvie have created some levels for you to spent your time on.
I must say that all credit goes to @cgarvie, for all his help on teaching us how to make levels and edit files etc.

He has now release a level pack of 10 custom levels:
up and over (@cgarvie)                        3 little pigs (@cgarvie)
through the wall (@cgarvie)                mind the steps (@stobbsc)
drop (@cgarvie)                                        pyramid (@cgarvie)
oh piggy where art thou (@cgarvie) bounce left right (@stobbsc)
roll over miss piggy (@cgarvie)            birdhouse of my soul (@cgarvie)

There is a video below of the levels in action:

Here are the instructions of how you can go ahead and install these levels:
First you need to download the attached file:HERE
You can either use WinRAR to extra the file on your PC or Type the following in your N900 terminal if you download it directly to your device:

root
tar xfz /home/user/MyDocs/cag_level_pack.tar.gz

This will extra a mypack folder. Copy this folder to the internal memory of the N900 if you unpacked in windows.
Then open X-Terminal (you will need rootsh) on the N900 an type in the following:

root
mkdir /home/opt/rovio/angrybirds/data/levels/pack2
cp /home/user/MyDocs/mypack/* -R /home/opt/rovio/angrybirds/data/levels/pack2

So a big thanks to everyone over at Maemo.org and to Rovio. now lets get playing.