Shashaqi Green Nose_The hourglass with small hands

Author: Shasha Qi green nose Publisher: Little Fish Light Book size: 210mm x 280mm Number of pages: 32 pages ISBN: 978-988-79958-1-4 【brief introduction】 An hourglass full of large and small stones will one day stop flowing. Small stones were piled up in the bottleneck, and other stones were also told not to flow past. What is the reason? Will there be a solution?