2D Ground Detection with OverlapCircle

Hello, I’m a newbie when it comes to Unity and Javascript. I’m making a game for a school project, a 2D platformer.
However, I am encountering a problem with my ground check, it’s always false! (Meaning that Unity thinks the player is still in the air, correct?).
There must be something wrong, but I can’t see it. Any help will be appreciated, thanks in advance!

This is my code:

var moveUp : KeyCode;
var moveDown : KeyCode;
var moveLeft : KeyCode;
var moveRight : KeyCode;

var isGrounded : boolean;
var groundCheck : Transform;
var groundRadius : float = 0.2;
var ground : LayerMask;


var jumpForce : int = 700;
var speed : float = 10;


function FixedUpdate ()
{
	isGrounded = Physics2D.OverlapCircle(groundCheck.position, groundRadius, ground);
}

function Update ()
{
	if (Input.GetKey(moveUp)) && isGrounded)
	{
		rigidbody2D.velocity.y = jumpForce;
	}	
	else if (Input.GetKey(moveLeft))
	{	
		rigidbody2D.velocity.x = speed * -1;
	}	
	else if (Input.GetKey(moveRight))
	{
		rigidbody2D.velocity.x = speed;
	}
}

Step 1:

You add the objects you want to a new or existing layer in the inspector (at the top right corner)

Step 2:

Then you define the layermask you want to check against :

Layermask myLayermask = 1 << LayerMask.NameToLayer ("myLayerName");

(Use this Layermask in your overlapCircle)

Btw, this example will ignore all layers exept the one with name ‘myLayerName’.