1. Cool!

2. Why use a staggered layout? Because people are used to it? Counterpoint: the numpad is not staggered and people are easily able to use both parts of a normal keyboard)

1) Thank you!

2) The staggered layout has been carefully chosen to allow for single-hand use. The user must be able to press up to three keys at the same time (2 modifiers and 1 symbol key). The layout I settled on for Mathpad makes this as easy as possible.

Interesting. Perhaps the fingers do want to go at a slight angle so making it a good choice :)

they don't, lateral moves (especially diagonal) are the least ergonomic for the fingers, your numpad insticts are closer to reality, though the best would be to "stagger" vertically to reflect the difference in finger length