The details about the pricing is still bit open so I can't comment any definitive about that yet, sorry.

However, the configuration is going to be little different from how we brought it out for iPhone. On iPhone there is only the paid app with 63 levels. On N900 in the spirit of open platform we actually made the fully working game with 21 levels free. In case you get addicted to it (and you will ) there will be also a separate paid level pack containing 42 more levels.

And as for more level packs, well, it's up to you.