menuImages=new Array(8);

for(i = 0; i <= 8; i++) {

  menuImages[i] = new Image(120,211)

}

menuImages[1].src = "./images/button_about_on.gif";

menuImages[2].src = "./images/button_hist_on.gif";

menuImages[3].src = "./images/button_miss_on.gif";

menuImages[4].src = "./images/button_write_on.gif";

menuImages[5].src = "./images/button_about_off.gif";

menuImages[6].src = "./images/button_hist_off.gif";

menuImages[7].src = "./images/button_miss_off.gif";

menuImages[8].src = "./images/button_write_off.gif";

rover=new Array(4);

for(i = 0; i <= 4; i++) {

  rover[i] = new Image(392,133)

  }

rover[0].src = "open-area.gif";

rover[1].src = "rover1.gif";

rover[2].src = "rover2.gif";

rover[3].src = "rover3.gif";

rover[4].src = "rover4.gif";

function on_image(i,x) { 

   x.src = menuImages[i].src;

   document.Z.src = "rover" + i + ".gif";

}



function off_image(i,x) { 

   x.src = menuImages[i+4].src;

   document.Z.src = "open-area.gif";

}