2D Player Controller

PlayerController.cs

using UnityEngine;
using System.Collections;

public class PlayerController : MonoBehaviour {

	//Player movement variables
	public float moveSpeed;
	public float jumpHeight;
	private bool doubleJump;

	//Player grounded variables
	public Transform groundCheck;
	public float groundCheckRadius;
	public LayerMask whatIsGround;
	private bool grounded;

	//Non-Stick Player
	private float moveVelocity;

	
	// Use this for initialization
	void Start () {
		
	}

	void FixedUpdate () {
		grounded = Physics2D.OverlapCircle(groundCheck.position, groundCheckRadius, whatIsGround);
	}

	// Update is called once per frame
	void Update () {

		// This code makes the character jump
		if(Input.GetKeyDown (KeyCode.Space)&& grounded){
			Jump();
		}

		// Double jump code
		if(grounded)
			doubleJump = false;

		if(Input.GetKeyDown (KeyCode.Space)&& !doubleJump && !grounded){
			Jump();
			doubleJump = true;
		}
		//Non-Stick Player
		moveVelocity = 0f;

		// This code makes the character move from side to side using the A&D keys
		if(Input.GetKey (KeyCode.D)){
			//GetComponent<Rigidbody2D>().velocity = new Vector2(moveSpeed, GetComponent<Rigidbody2D>().velocity.y);
			moveVelocity = moveSpeed;
		}
		if(Input.GetKey (KeyCode.A)){
			//GetComponent<Rigidbody2D>().velocity = new Vector2(-moveSpeed, GetComponent<Rigidbody2D>().velocity.y);
			moveVelocity = -moveSpeed;
		}

		GetComponent<Rigidbody2D>().velocity = new Vector2(moveVelocity, GetComponent<Rigidbody2D>().velocity.y);


	}

	public void Jump(){
		GetComponent<Rigidbody2D>().velocity = new Vector2(GetComponent<Rigidbody2D>().velocity.x, jumpHeight);
	}
}

void FixedUpdate() {

    move = Input.GetAxis ("Horizontal");
    grounded = Physics2D.OverlapCircle (groundCheck.position, groundCheckRadius, whatIsGround);
    player.velocity = new Vector2 (move * moveSpeed, player.velocity.y);
}