I rocketed through most of the easy difficulty levels. Maybe this game is aimed at people younger than Ph.Ds like myself. The expert difficulty level was more of a challenge at first, and in my opinion should be made available earlier. Once I got some upgrades I started rocketing through that level too. There are some nice features, like opponents with different abilities and special tiles. For someone developing their vocabulary it could be a very fun game. I got through it without spending any real world money. There were a few ads at the bottom, but I did not find them to be intrusive.