The first 20 levels or so are free. After that, I think the rest costs $1.99. I paid it.
Altogether there are 51 levels and I'm stuck on 45, which I think is too hard!
This blog focuses on GREAT, FUN PUZZLE APPS for the ipad, iphone and ipod. If you are creating your own puzzle app and want it reviewed, contact me at LinkedIn. Tom Cutrofello