Unity

        [SerializeField]
        private float speed;

        [SerializeField]
        private float jumpHeight;

        [SerializeField]
        private float gravity;

        [SerializeField] private Vector3 direction;

        private new Rigidbody2D rigidbody2D;

        private void Awake()
        {
            rigidbody2D = GetComponent<Rigidbody2D>();
        }

        private void Update()
        {
            if (!OnGround())
            {
                direction.y -= gravity * Time.deltaTime;
                return;
            }

            if (Input.GetKeyDown(KeyCode.Space))
                direction.y = jumpHeight;

            direction = new Vector3(Input.GetAxis("Horizontal") * speed, direction.y, direction.z);
        }

        private void FixedUpdate()
        {
            rigidbody2D.velocity = direction;
        }

        private bool OnGround()
        {
            return Physics2D.Raycast(transform.position, Vector2.down, 1, LayerMask.GetMask("Floor"));
        }