Game development advice

[pdsoft]

Im currently working on a puzzle game and I have about 30 levels planned. I was thinking of offering 15 for free and locking the rest behind a paywall.
Im looking for some advice on this, Is 15 too much or too little to offer for free? I was thinking of designing 40-50 levels total, but since this is the mobile platform maybe 30 total, 15 free would be satisfactory.
Im familiar with how things work for flash games. 30 levels total is fine for the average sponsored flash game but I don't have much experience with app stores. Is this sort of things acceptable for the 99 cents price tag? or will there be lots of complaints.
I know it depends on the quality of the game but Im hoping for some advice from someone who has done something similar already.

Thanks

[Verbage]

I would offer both a lite and a paid version. Apple does not like "demo" apps where you have to pay to use the rest of the app.

[pdsoft]

I did notice that there aren't any lite games with unlockable content, so its because apple rejects them. Its a shame, seems like it would offer the most turn over.

[AndyH]

Isn't that what In-App-Purchases are for?

[pdsoft]

Ive been looking for games that utilize IAP for unlocking levels, I can't find anything that isn't considered bonus content, rather than actual content for a complete game.

[JoKa]

A game must not look crippled or incomplete. I have the same problem and hope it'll be fine to simply split the levels into packs of 16. One pack free, others available as IAP. Many devs use lite/full versions, but Twitty 2 is an example that offers additional levels as IAP.