You are the green box. To pass a level, you will have to reach the yellow box. The black tiles are obstacle that you can't move. The blue tiles are movable obstacles. To absorbe a blue tile, press the spacebar key. When you absorbe a blue tile, you can't release it : you have to deals with the new shape of your character.
Eight level are implemented. Feel free to create your own using every image editor you want : levels are in png. You just will have to name it lvl<your-level-number>.png in the assets/level directory. The game load all the level one by one.