Can't seem to get collision to work among my sprites

Hey guys - I’m working on a top down brawl game and i have this little ball in a circle shaped arena. I drew an arrow on top of the ball to see in which direction it’s facing. The arena is a sprite i have imported (blank rectangle with a circle in the middle).

I added an empty game object as a child of this arena, gave it a rigidbody2d and a circle collider. My movable “player-ball” should only be able to move within that given circle (the arena). No the problem is, that the collision between player and circle edge does not trigger. Both objects have a rigidbody2d and the circle collider of the arena has “is trigger” checked…i’ll post my code below - maybe someone can give ma some insight.

Thx for any help!
Codes in C# btw :wink:

using UnityEngine;
using System.Collections;

public class Player_Movement : MonoBehaviour 

	private Vector2 movementVector;

	private float movementSpeed = 8;
	// Use this for initialization

	private float heading;
	private Quaternion rotationToHold;

	private bool movingX;
	private bool movingY;

	public bool wallTrigger;

	void Start () 


	// Update is called once per frame
	void Update () 
		movementVector.x = Input.GetAxis ("LeftJoystick_X") * movementSpeed;
		movementVector.y = Input.GetAxis ("LeftJoystick_Y") * movementSpeed;
		///Moving the Player
		GetComponent<Rigidbody2D>().velocity = new Vector2 (movementVector.x, movementVector.y*(-1));

		///turning the player
		float heading = Mathf.Atan2(movementVector.x*(-1), movementVector.y*(-1));

		transform.rotation = Quaternion.Euler (0f,0f,heading*Mathf.Rad2Deg);

		//movement checks in order to keep rotation after letting go of stick
		if (movementVector.x == 0)
			movingX = false;
			movingX = true;

		if (movementVector.y == 0) {
			movingY = false;
		} else {
			movingY = true;

		if (movingX || movingY == true) {
			rotationToHold = transform.rotation;
		} else {
			transform.rotation = rotationToHold;

		///check if Player is inside the arena and restric his movement if not
		if (wallTrigger == true) {
			movementSpeed = 0;
		} else {
			movementSpeed = 8;

	void OnTriggerEnter (Collider other)
		wallTrigger = false;

	void OnTriggerExit (Collider other)
		wallTrigger = true;

Assuming you’re using the 2d physics system ( and it seems that you are), you need the 2D version of the Trigger handlers. Specifically…