Deep learning has been widely and actively used in various research areas.Recently,in gauge/gravity duality,a new deep learning technique called AdS/DL (Deep Learning) has been proposed.The goal of this paper is to explain the essence of AdS/DL in the simplest possible setups,without resorting to knowledge of gauge/gravity duality.This perspective will be useful for various physics problems:from the emergent spacetime as a neural net-work to classical mechanics problems.For prototypical examples,we choose simple classical mechanics problems.This method is slightly different from standard deep leaming techniques in the sense that we not only have the right final answers but also obtain physical understanding of learning parameters.