message: Re-use mathSign util
diff: import { Limit } from './limit'
  +import { mathSign } from './utils'
  type Params = {
  start: number
  @@ -33,7 +34,7 @@ export function Counter(params: Params): Counter {
  function add(n: number): Counter {
  if (n !== 0) {
  - const sign = n / Math.abs(n)
  + const sign = mathSign(n)
  set(get() + sign)
  return add(n + sign * -1)
  }
  