const state = proxy({
    dur: 4,
    count: 1
  });
  const incDur = () => {++state.dur};
  const decDur = () => {--state.dur};
  const incCount = () => {
    ++state.count;
    setTimeout(incCount, 100 * state.dur);
  };

  incCount();

  const snap = useSnapshot(state)

  return (
    <div>
      <h3>{snap.dur}</h3>
      <button
        disabled={snap.dur <= 1}
        onClick={decDur}>
        -
      </button>
      <button
        disabled={snap.dur >= 10}
        onClick={incDur}>
        +
      </button>
    </div>
  );