It was sunny today. After school, I unintentionally built something interesting using my electronic snap circuits. Initially, I was building a simple fan with a motor, a keyset, and a battery case. The purpose was to create a gust of air, but I connected the wires backwards, causing the propeller to spin in reverse. As a result, no gust was blowing out. However, when I released the keyset, something unexpected happened—the propeller took off, soared up to the ceiling, and hovered for a short while. It turns out I had inadvertently built an electric bamboo copter. In hindsight, It was a valuable lesson, as I discovered the concept of positive-negative rotation.