// #region game core
// ...
const getStateAfterMoveProcessing = (state, movement, distance) => {
  const newTail = getNewTail(state.snake, distance)
  const oldHead = getLastElement(state.snake)
  const newHead = oldHead.add(state.direction.scaleBy(distance))
  const newDirection = getNewDirection(state.direction, movement)
  if (!state.direction.equalTo(newDirection)) {
    const { x: oldX, y: oldY } = oldHead
    const [
      oldXRounded,
      oldYRounded,
      newXRounded,
      newYRounded
    ] = [oldX, oldY, newHead.x, newHead.y].map(Math.round)
    const getStateWithBrokenSnake = (old, oldRounded, newRounded, getBreakpoint) => {
      const breakpointComponent = oldRounded + (newRounded > oldRounded ? 0.5 : -0.5)
      const breakpoint = getBreakpoint(breakpointComponent)
      const vector = newDirection.scaleBy(distance - Math.abs(old - breakpointComponent))
      const head = breakpoint.add(vector)
      return {
        ...state,
        direction: newDirection,
        snake: [...newTail, breakpoint, head]
      }
    }
    if (oldXRounded !== newXRounded) {
      return getStateWithBrokenSnake(oldX, oldXRounded, newXRounded, x => new Vector(x, oldY))
    }
    if (oldYRounded !== newYRounded) {
      return getStateWithBrokenSnake(oldY, oldYRounded, newYRounded, y => new Vector(oldX, y))
    }
  }
  return {
    ...state,
    snake: [...newTail, newHead]
  }
}