Daily Chinese Idiom Guessing Game
To produce immediate results; to have an instant effect.
在阳光下把竿子竖起来，立刻就看到影子。比喻立刻见到功效。
汉·魏伯阳《参同契》卷下立竿见影，呼谷传响。”
The new marketing strategy was like setting up a pole and seeing its shadow; sales increased immediately.