Must be a first timer...
Nice and fun game, if you want to be able to hold buttons instead of having to press, use
Input.GetKey
not
Input.GetKeyDown
or even better, use Input.GetAxis("Vertical")
which u can then insert directly into
[rigidbody].move(new Vector3(0, [var], 0));
or
transform.position += new Vector3(0, [var], 0)
Goodluck on your game making journey :)