[SerializeField]
private float speed = 5;
[SerializeField]
private float gravity = -20;
[SerializeField]
private LayerMask collisionMask;

private BoxCollider2D boxCollider;
private Vector2 groundNormal;

private void Awake()
{
    boxCollider = GetComponent<BoxCollider2D>();
}

private void Update()
{
    float playerInput = Input.GetAxisRaw("Horizontal");

    velocity.x = playerInput * speed;
    velocity.y += gravity * Time.deltaTime;

    MoveCharacter(velocity * Time.deltaTime);
}

private void MoveCharacter(Vector2 velocity)
{
    //Rotate the character
    Quaternion targetRotation = Quaternion.FromToRotation(Vector2.up, groundNormal);
    transform.rotation = Quaternion.Lerp(transform.rotation, targetRotation, 0.5f);

    groundNormal = Vector2.zero;

    CollideBelow(ref velocity);
    transform.Translate(velocity);
}

private void CollideBelow(ref Vector2 deltaMovement)
{
    float rayLength = 1;
    Vector2 rayOrigin = transform.position;

    RaycastHit2D hit = Physics2D.Raycast(rayOrigin, -transform.up, rayLength, collisionMask);
    Debug.DrawRay(rayOrigin, -transform.up * rayLength, Color.red);

    if (hit)
    {
        velocity.y = 0;
        deltaMovement.y = -(hit.distance - boxCollider.size.y * 0.5f);

        groundNormal = hit.normal;
    }
}