Added minor UI changes. Field draws with different colors in order to visualize different cells. Changed cell colors, because probably we will need more contrast colors for the presentation in order to be visible. Changed the way blown cells are displayed. Now all area, which is blown will change it's color, so it's with the same color. It looks more like some inactive zone on the playfield. I made these changes without (especially about the colors) without speaking with anybody else, so fell free to revert them, if you don't like them.