Move Link in 4 Directions

[Hurdarr]

Greetings all. For educational purposes, I'm trying to clone The Legend of Zelda (NES) Link's movement.

This what I have:

stop();

var leftKeyDown:Boolean = false;
var upKeyDown:Boolean = false;
var rightKeyDown:Boolean = false;
var downKeyDown: Boolean = false;

var linkSpeed:Number= 7;

// Link Movement

Link.addEventListener(Event.ENTER_FRAME, moveLink);

function moveLink(event:Event):void
{
    if(leftKeyDown)
    {
        Link.x -= linkSpeed;
    }
    
    if(rightKeyDown)
    {
        Link.x += linkSpeed;
    }
    
    if(upKeyDown)
    {
        Link.y -= linkSpeed;
    }
    
    if(downKeyDown)
    {
        Link.y += linkSpeed;
    }
}

// Keys are pressed

stage.addEventListener(KeyboardEvent.KEY_DOWN, checkKeysDown);

function checkKeysDown(event:KeyboardEvent):void
{
    if(event.keyCode == 37)
    {
        leftKeyDown = true;
    }
    
    if(event.keyCode == 38)
    {
        upKeyDown = true;
    }
    
    if(event.keyCode == 39)
    {
        rightKeyDown = true;
    }
    
    if(event.keyCode == 40)
    {
        downKeyDown = true;
    }
}

// Keys are loose

stage.addEventListener(KeyboardEvent.KEY_UP, checkKeysUp);

function checkKeysUp(event:KeyboardEvent):void
{
    if(event.keyCode == 37)
    {
        leftKeyDown = false;
    }
    
    if(event.keyCode == 38)
    {
        upKeyDown = false;
    }
    
    if(event.keyCode == 39)
    {
        rightKeyDown = false;
    }
    
    if(event.keyCode == 40)
    {
        downKeyDown = false;
    }
} 

Link can move in eight directions, what do I need to remove his diagonal movements?

Thanks.