Door Door is a platform game where players control Chun, who aims to trap four different alien types behind doors. The objective of the game is for Chun to capture as many aliens as possible and lock them behind each available door on a stage. Chun must quickly close the door after sliding it open, as if he waits too long, the trapped aliens will escape and pursue him again.
The gameplay revolves around Chun's efforts to trap aliens, with each stage completed when all four types are successfully locked behind doors. The player must master the timing of closing the door to succeed in capturing the creatures, adding a sense of urgency to the action-packed platforming.