They're the best free apps I've ever played, but it's worth throwing a few bucks at the developers for such spectacularly well-designed games! (And no, I don't know any of the developers. Get these, and then pay for the upgrades. While the only noticeable difference is that Titan is in portrait mode and Epic is in landscape - so it's just a matter of tilting the iPad sideways to play one or the others - I've actually solved all 1650 boards available in Titan, but there's one in Epic I'm convinced is unsolvable.
Honestly, I prefer this one to its sister game.
And the customizability is nearly endless. These games are so beautiful, so relaxing, and so addictive that I've spent eight months solving the 3300 boards they offer (plus the new daily games!), and I may just start all over again. Free tiles are those that do not have anything on top of them and are free to access from either the left or right. Tiles can be removed by finding a matching pair but only free tiles can be picked up. I played a lot of mahjong games over the years before I found the two from Kristanix - and now I've pretty much stopped playing anything else. Your goal is to remove all of the tiles from the board. One of the two best games in the App Store