nav1_on = new Image; 
			nav1_off = new Image;
			nav1_on.src = "imgs/nav1_on.gif";
			nav1_off.src = "imgs/nav1_off.gif";
			
			nav2_on = new Image; 
			nav2_off = new Image;
			nav2_on.src = "imgs/nav2_on.gif";
			nav2_off.src = "imgs/nav2_off.gif";
			
			nav3_on = new Image; 
			nav3_off = new Image;
			nav3_on.src = "imgs/nav3_on.gif";
			nav3_off.src = "imgs/nav3_off.gif";
			
			nav4_on = new Image; 
			nav4_off = new Image;
			nav4_on.src = "imgs/nav4_on.gif";
			nav4_off.src = "imgs/nav4_off.gif";
			
			nav5_on = new Image; 
			nav5_off = new Image;
			nav5_on.src = "imgs/nav5_on.gif";
			nav5_off.src = "imgs/nav5_off.gif";
			
			nav6_on = new Image; 
			nav6_off = new Image;
			nav6_on.src = "imgs/nav6_on.gif";
			nav6_off.src = "imgs/nav6_off.gif";
			
			function swapem(fusion, planet) {
			fusion.src = planet.src;
}