tapability

[gurgeous]

Great app! I have three feature requests that are related to iOS taps:

1. Would it be possible to stretch the skin a big taller for the iOS 414x736 form factor? More space would be nice.
2. Instead of requiring the user to precisely tap each key, can we route the tap to the closest key? Right now around half my taps end up not doing anything because the hit boxes are small.
3. Can we have the phone vibrate on each button tap? Some other calc apps do this and I find it very helpful.

Might be able to assist with some of these if you are open to PRs... Thanks!