I have the Mac's Magic Keyboard with Numpad:
The keys are very shallow and each if about the size of my thumb. I play the game by placing my left hand so each of my fingers is over 1-5. The issues is that my thumb is much shorter than my other fingers. This means to hover over the 5 key I have to twist my wrist to my thumb is over the key (making it harder to hit the other keys) or really push my thumb forward (my thumb then ends up parallel to the key, making it hard to press down without hitting a bunch of other keys). This issue with my thumb exacerbates the difficulty of crossing your fingers (or whatever the actual name is when playing piano) when switching from 1-5 to higher notes and back.