# Requirement change

Some of our users have asked for a fourth way to split a bill. Percentages are fiddly when what
you actually mean is "shares" — like splitting rent by room size, or splitting a family dinner
where the kids' portions count for less.

**Add a `SHARES` split.** Each participant is given a whole number of shares — could be
`2, 1, 1`, could be `5, 3, 2`, whatever the group agrees. The amount is divided in proportion to
the shares: with weights `2:1:1` on a bill, the first participant's cut is twice the second's and
twice the third's, and the second and third get the same amount as each other.

A few things that do not change, because someone always assumes they do:

- **The usual remainder rule still applies.** If dividing proportionally does not come out even in
  whole minor units, the leftover goes to the first participants listed, exactly as it does for an
  equal split today.
- **A share of zero is legal.** Someone who is "in the group chat" but didn't have any of the
  thing being split can be given `0` shares and owe nothing for it. What is not legal is every
  share being zero — there has to be something to divide the amount in proportion *to*.
- **Everything else about an expense is unchanged**: the payer rule, the self-expense rule, how
  balances move, all of it.
