Getting NullReferenceException when changing velocity for a Rigidbody2D

Questions & Answers
1

I’m trying to program a simple Goomba-type enemy in my 2D game that simply walks forward until it hits a wall and then turn around.

I wrote it with a RigidBody2D and changed it’s velocity, see code below.

using UnityEngine;
using System.Collections;

public class SmallCritter : MonoBehaviour {
	public float moveSpeed;
	bool isMirrored = false;
	Rigidbody2D rb2D;

	void start() {
		rb2D = GetComponent<Rigidbody2D> ();
	}

	void FixedUpdate() {
		if (isMirrored) {
			rb2D.velocity = new Vector2 (moveSpeed, rb2D.velocity.y);
		} else {
			rb2D.velocity = new Vector2 (-1 * moveSpeed, rb2D.velocity.y);
		}
	}

However, when starting the game, I get this issue:
"NullReferenceException : Object reference not set to an instance of an object.

I checked and doubled checked the code, but I can’t figure out why this doesn’t work (the moveSpeed variable is set in Unity).

Can anyone help me?

2

Start is misspelled. The first letter needs to be uppercase.