Thanks so much for playing and thanks for asking directly :) At the start of the game, it says to clear each room to advance to the next one, so the idea is to defeat all the enemies in the room to get into the next one. In actuality, each door has a timer (which is generally around 10 - 15 seconds) so you only have to survive that long to advance. The only problem is that the door unlocking isn't made clear with any audio or visual queues, so I should fix that! Thank you for playing my game :)