This is a pretty fun game. The logic for moving the marble could be a little smarter (or at least *explained*) - it liked to trap me with movement that didn't seem logical. If I set up a board like

where S is start, R is rock, and G is gem, it would move me like

which would have me trapped where the Gem used to be. The movement I expected was

There were other similar situations, such as the marble moving itself onto a trapped death-square (trapped as it was a dead-end) instead of going the straight path to the exit. This was on the level with the bombs after hitting the second bomb and swapping the skulls - I tried to move to the end and it moved me left instead

Marble-moving logic aside, this game is fun but just a bit too pricey given the estimated replay value (since I don't think 100 levels will take that long to get through). If a vibrant community of level-builders sprung up (and thus replay value given a big boost) I'd probably buy it, but without that I'll have to think long and hard about spending $20 on this.

But once again, I do say this is a very fun game. For those of you who haven't, try the demo!