var timer, layer	;	
		
		function start() {
			var fixed_edge, moving_edge, end_pos, hor_move = null, oper;
			if ((from_pos == "left" || from_pos == "right") && (what_half != 1 && what_half != 2)) {
			alert ("You must assign 'what_half' either '1' or '2' when 'from_pos' = 'left' or 'right'") }
			if ((from_pos == "middle") && (direction != "up" && direction != "down")) {
			alert ("You must assign a 'direction' of 'up' or 'down' when 'from_pos' = 'middle'") }
			if ((from_pos != "middle") && (from_pos != "right") && (from_pos != "left") && (from_pos != "bottom") && (from_pos != "top")) {
			alert ("You must assign a from_pos movement of top, right, left, bottom, or middle") }
			if ((from_pos == "middle") && (direction == "up") && (activelayer != "toplayer")) {
			alert ("When assigning 'middle' and 'up', activelayer must be 'toplayer'") }
			if ((from_pos == "middle") && (direction == "down") && (activelayer != "botlayer")) {
			alert ("When assigning 'middle' and 'up', activelayer must be 'toplayer'") }
						
			set_starting_pos(); 
			document.getElementById(activelayer).style.visibility = "visible";
			}
			
		
		function set_starting_pos(){	
		
			switch (from_pos) {
				case "left":
					fixed_edge = (what_half == 1) ? 0 : 280;
					moving_edge = -300;
					end_pos = 150;
					oper = "+";
					direction = "up" //moving from left to right
					hor_move = 1;
					break;
				case "right":
					fixed_edge = (what_half == 1) ? 0 : 280;
					moving_edge = 610;
					end_pos = 150;
					oper = "-";
					direction = "down" //moving from right to left
					hor_move = 1;
					break;
				case "top":
					moving_edge = -280;
					fixed_edge = 150;
					end_pos = 0;
					oper = "+";
					direction = "down";
					hor_move = null;
					break;
				case "bottom":
					moving_edge = 560;
					fixed_edge = 150;
					end_pos = 280;
					oper = "-"
					direction = "up";	
					hor_move = null		
					break;
				case "middle":
					moving_edge = (direction == "up") ? 280 : 0;
					oper = (direction == "up") ? "-" : "+";
					end_pos = (direction == "up") ? 0 : 280;
					document.getElementById("toplayer").style.zIndex = (direction == "up") ? 1 : 3;
					document.getElementById("botlayer").style.visibility = (direction == "up") ? "visible" : "hidden";
					document.getElementById("toplayer").style.visibility = (direction == "down") ? "visible" : "hidden";
					fixed_edge = 150;
					hor_move = null
					break;
				}


				layer = document.getElementById(activelayer)
				if (hor_move) {
					layer.style.left = moving_edge+"px";;
					layer.style.top = fixed_edge+"px";;
					} else { 
					layer.style.left = fixed_edge+"px";
					layer.style.top = moving_edge+"px"; 
					}

				}
			
			
		function loopIt() {
			moveIt();
				if (hor_move) {
					if (direction == "up" && moving_edge >= end_pos) { return;}	//return = done!
					else if (direction == "down" && moving_edge <= end_pos) { return; }
					} else {
					if (direction == "up" && moving_edge <= end_pos) { return;}	//return = done!
					else if (direction == "down" && moving_edge >= end_pos) { return; }
					}
			timer = setTimeout('loopIt()',delay);
			}
			
			
		function moveIt() {

			eval("moving_edge = moving_edge"+oper+"step");    //figure amount to move

			layer = document.getElementById(activelayer)
			if (hor_move) {
				layer.style.left = moving_edge+"px";;
				layer.style.top = fixed_edge+"px";;
				} else { 
				layer.style.left = fixed_edge+"px";
				layer.style.top = moving_edge+"px"; 
				}
			}