Looks good!

(Pdb) print(b.mask_[3,:])
[[False False False False False False False False False False False]
[False False False True True True True True False False False]
[False False True True True True True True True False False]
[False True True True True True True True True True False]
[False True True True True True True True True True False]
[False True True True True True True True True True False]
[False True True True True True True True True True False]
[False True True True True True True True True True False]
[False False True True True True True True True False False]
[False False False True True True True True False False False]
[False False False False False False False False False False False]]

@lcnature, regardless of your off-by-one question (@mjanderson09?), please add unit tests for the new Ball class to pass the coverage check.

@mihaic Done. Thanks!

Thanks, @lcnature. I am sure your Ball shape will be very popular.