The Voxel Agents is a development firm that's seen a lot of success with the Train Conductor apps, a set of puzzle games where you guide trains across a series of parallel tracks, attempting to keep them from crashing for as long as possible. The company has been working on a new game for quite a while, one that I originally saw last year at GDC as "Project: Tree." At the time, the game looked fairly unfinished, to the point where I passed on covering it, shelving it away to see how it turned out at release.
As you can see over on the company blog, Voxel Agents worked very hard on the title and its puzzles over the next year, and it has now emerged on the App Store as a game called Puzzle Retreat. The game I saw last year is very different in theme from the game out now, though the mechanic is generally the same: you have a small grid of squares with pieces on each end that you can slide forward to "fill in" open spaces, and the key is that pieces you push will slide across any filled spaces, making the goal to fill in all of the spaces on the grid. It sounds complicated but like any great puzzle game, it's fairly easy to understand in execution. Later parts of the game present some more tricks, like pieces that will slide more than one place at a time, or blocks that will stop others and need to be placed last.
The game I saw had tree-like creatures and seeds sliding around, but Voxel wisely chose to make the pieces of the game into wood and ice, creating objects that are a little more and easy to understand. Puzzle Retreat is a solid puzzle game, and you can tell it's the product of a lot of hard work and consideration. The game is available for US$0.99, and it comes with 96 different puzzles to solve across two packs. If that's not enough for you, there are more puzzle packs available for 99 cents each, with 24 more puzzles each to solve.