The key is to follow the ying/yang theme by tapping the spaces above the door to be the exact opposite as the ones already done below the door like in the image below:
Tactical, beautiful, and wholly unique, the GOTY-winning sci-fi RTS returns with Homeworld 3. Assume control and battle through fleet combat in dazzling, fully 3D space while the award-winning story unfolds on a galactic scale.