You have to conquer what is hidden under the '?' tiles, conquer all tiles of a certain color or shape, walk around all the place and much more! Only after completing totally a certain level you can pass to the next one. There's 4 sets of levels in the 'Lock & Key' mode; 2 in the 'Pyramid' mode and 2 in the 'Spatial Frog'. In each level it's easy to see wat is the goal. The game offers a great variety of puzzles and scenes. You can also pass to the 'Construction zone', where you can design the scenes you want, for all the game modes; or to the 'Warehouse', where you can load scenes created by other users online, but you'll need an access key to do it.
Arrow keys to move; you can go to empty tiles, but also to filled spaces if you want to push them to observe the consequences.