Keep the interface monochrome — warm paper, near-black ink, one black button. No accent hue in the chrome.
Let deck themes carry all the color, applied only to slide content.
Set everything in Diatype; go large with tight negative tracking for display.
Keep radii small (4px buttons) and borders hairline — editorial, not soft.
Make theming the hero: switching a deck theme re-skins every slide at once.