plz use code tag
OP has local function problems, remove “private” from void OnCollisionEnter2D should remove the error
how ever I dont know if it ok to have OnCollisionEnter2D as a local function.
void PlayerJump()
{
if (Input.GetButtonDown("Jump") && isGrounded)
{
isGrounded = false;
myBody.AddForce(new Vector2(0f, jumpForce), ForceMode2D.Impulse);
}
void OnCollisionEnter2D(Collision2D collision)
{
if (collision.gameObject.CompareTag(GROUND_TAG))
{
isGrounded = true;
}
}
}