Replaced the World image with a simple color background and introduced dynamic water system (not as cool as it sounds). Using a simple wave function and playing with the variables based on 'current_tide_leve' and a couple other things. Also this introduces the first structure sprites and tiling mechanism. They are not yet bound to anything in the game from a construction perspective but there is a build_castle test that wuns with the game to give a sense of the structure placement architecture (very simple tiled graphics.