Designing for Microsoft HoloLens meant starting from scratch. There were no established conventions for holographic interfaces — no pixel grids, no standard interaction patterns, no prior art to reference. We found ourselves learning Unity 3D, measuring layouts in metres instead of pixels, and testing ideas directly in physical space with the Umbra engineering team. Four principles guided the work. The UI follows the user with a slight delay — always nearby, never blocking the content. It fades out unless needed, so the model stays front and centre. Every action can be performed two ways — a direct drag in real space or a shortcut tap — because architects and engineers need both depending on distance and precision. And the interface hides automatically based on hand position, protecting the limited field of view of current headsets. Each principle came from observation, testing, and iteration — not from a pattern library. Login by QR code, menu items summoned mid-air, typography tested at arm's length in a real room. This was design at the beginning of a new computing era.