C# Unity3D Ball Physics - Advanced

Vector3 newPosition = transform.localPosition + displacement;
transform.localPosition = newPosition;
velocity = body.velocity;
        float maxSpeedChange = maxAcceleration * Time.deltaTime;
        velocity.x =
            Mathf.MoveTowards(velocity.x, desiredVelocity.x, maxSpeedChange);
        velocity.z =
            Mathf.MoveTowards(velocity.z, desiredVelocity.z, maxSpeedChange);
        body.velocity = velocity;
void Update () {
        Vector2 playerInput;
        playerInput.x = Input.GetAxis("Horizontal");
        playerInput.y = Input.GetAxis("Vertical");
        playerInput = Vector2.ClampMagnitude(playerInput, 2f);
new Vector3(playerInput.x, 1f, playerInput.y) * maxSpeed;
    }
void FixedUpdate () {
        velocity = body.velocity;
        float maxSpeedChange = maxAcceleration * Time.deltaTime;
        velocity.x =
            Mathf.MoveTowards(velocity.x, desiredVelocity.x, maxSpeedChange);
        velocity.z =
            Mathf.MoveTowards(velocity.z, desiredVelocity.z, maxSpeedChange);
        body.velocity = velocity;
    }
bool desiredJump;
void Update () {
    desiredJump |= Input.GetButtonDown("Jump");
    void FixedUpdate () {
        if (desiredJump) {
            desiredJump = false;
            Jump();
        }
        body.velocity = velocity;
    }

    void Jump() {
        velocity.y += 5f;
    }
        [SerializeField, Range(1f, 100f)]
    float jumpHeight = 3f;
    void Jump () {
        velocity.y += Mathf.Sqrt(-3f * Physics.gravity.y * jumpHeight);
    }
    bool onGround;
        void OnCollisionEnter (Collision collision) {
        EvaluateCollision(collision);
    }
    void OnCollisionStay () {
        onGround = true;
    }
    void Jump () {
        if (onGround) {
            velocity.y += Mathf.Sqrt(-3f * Physics.gravity.y * jumpHeight);
        }
    }
    void FixedUpdate () {
        onGround = false;
    }
    Vector3 normal = collision.GetContact(i).normal;
            onGround |= normal.y >= 0.9f;
    [SerializeField, Range(0, 5)]
    int maxAirJumps = 0;
    int jumpPhase;
    void FixedUpdate () {
        UpdateState();
    }
    void UpdateState () {
        velocity = body.velocity;
        if (onGround) {
            jumpPhase = 0;
        }
    }
    void Jump () {
        if (onGround || jumpPhase < maxAirJumps) {
            jumpPhase += 1;
            velocity.y += Mathf.Sqrt(-3f * Physics.gravity.y * jumpHeight);
        }
    }
    jumpPhase += 1;
    float jumpSpeed = Mathf.Sqrt(-3f * Physics.gravity.y * jumpHeight);
            if (velocity.y > 0f) {
                jumpSpeed = Mathf.Max(jumpSpeed - velocity.y, 0f);
            }
            velocity.y += jumpSpeed;
    [SerializeField, Range(1f, 100f)]
    float maxAcceleration = 20f, float acceleration = onGround ? maxAcceleration : maxAirAcceleration;
        float maxSpeedChange = acceleration * Time.deltaTime;
    [SerializeField, Range(0f, 90f)]
    float maxGroundAngle = 25f;
    float minGroundDotProduct;
    void OnValidate () {
        minGroundDotProduct = Mathf.Cos(maxGroundAngle);
    }
    void Awake () {
        body = GetComponent<Rigidbody>();
        OnValidate();
    }
    minGroundDotProduct = Mathf.Cos(maxGroundAngle * Mathf.Deg2Rad);
    void EvaluateCollision (Collision collision) {
        for (int i = 0; i < collision.contactCount; i++) {
            Vector3 normal = collision.GetContact(i).normal;
            if (normal.y >= minGroundDotProduct) {
                groundContactCount += 1;
                contactNormal += normal;
            }
        }
    }
   void UpdateState () {
        velocity = body.velocity;
        if (onGround) {
            jumpPhase = 0;
        }
        else {
            contactNormal = Vector3.up;
        }
    }
    void UpdateState () {
        velocity = body.velocity;
        if (onGround) {
            jumpPhase = 0;
        }
        else {
            contactNormal = Vector3.up;
        }
    }
    void Jump () {
        if (onGround || jumpPhase < maxAirJumps) {
            velocity += contactNormal * jumpSpeed;
        }
    }
    float jumpSpeed = Mathf.Sqrt(-3f * Physics.gravity.y * jumpHeight);
            float alignedSpeed = Vector3.Dot(velocity, contactNormal);
            if (alignedSpeed > 0f) {
                jumpSpeed = Mathf.Max(jumpSpeed - alignedSpeed, 0f);
            }
            velocity += contactNormal * jumpSpeed;
    Vector3 ProjectOnContactPlane (Vector3 vector) {
        return vector - contactNormal * Vector3.Dot(vector, contactNormal);
    }
    void AdjustVelocity () {
        Vector3 xAxis = ProjectOnContactPlane(Vector3.right);
        Vector3 zAxis = ProjectOnContactPlane(Vector3.forward);
    }
    Vector3 xAxis = ProjectOnContactPlane(Vector3.right).normalized;
    Vector3 zAxis = ProjectOnContactPlane(Vector3.forward).normalized;
        float currentX = Vector3.Dot(velocity, xAxis);
        float currentZ = Vector3.Dot(velocity, zAxis);
    float acceleration = onGround ? maxAcceleration : maxAirAcceleration;
        float maxSpeedChange = acceleration * Time.deltaTime;
        float newX =
            Mathf.MoveTowards(currentX, desiredVelocity.x, maxSpeedChange);
        float newZ =
            Mathf.MoveTowards(currentZ, desiredVelocity.z, maxSpeedChange);
    velocity += xAxis * (newX - currentX) + zAxis * (newZ - currentZ);
    void ClearState () {
        groundContactCount = 0;
        contactNormal = Vector3.zero;
    }
    void UpdateState () {
        velocity = body.velocity;
        if (OnGround) {
            jumpPhase = 0;
            if (groundContactCount > 1) {
                contactNormal.Normalize();
            }
        }
    }
//This is a very old script I made a year ago in Unity3D and never used so apologies if it doesn't work, I just learnt it from an old YouTube tutorial so it may be broken! (same as: https://pastebin.com/Sj7i5JiU)