Pick one of Cantrip's twelve themes and most people assume that's the whole decision. Monk or sorcerer, done, move on to writing your About page. There's actually a second layer most people never open: a page of design settings sitting right below the theme grid that lets you tune fonts, corners, shadows, hover effects, and banner style without touching a line of CSS.
It's called Advanced Design Configuration, and it's genuinely useful. Pick a font pairing: System Sans if you want it invisible, Serif Pairing or Elegant Serif if you want some personality, Bold Display if you want headlines that shout a little. Pick how sharp your corners are: sharp, soft, round, or a cut corner that looks a bit like a name tag. Pick a shadow style, anywhere from nothing at all to a hard, comic-panel bold shadow to a soft glow. Pick what happens when someone hovers a button or card: nothing, a highlight, a lift, a grow, a glow. Pick how your banner photo gets treated: plain, a dark fade at the bottom for text legibility, or a tint in your brand color. Every change previews live before you save it.
Here's the part nobody tells you. Those five settings aren't independent of your theme. Each theme ships with its own defaults for all five, and when you click "Apply Theme" on a different one, Cantrip doesn't just swap the theme. It resets your fonts, corners, shadows, hover effect, and banner overlay back to whatever that new theme shipped with, silently, in the same click. Spend twenty minutes getting your corners and shadow just right, decide to try a different theme next week, and that work is gone the moment you hit apply. Not deleted exactly. Overwritten.
That's not a bug. It's the honest tradeoff of a preset system. A theme is supposed to be a coherent starting point, not just a color swap, and if switching themes left your old font pairing and shadow style bolted onto a completely different layout, plenty of combinations would look like a mistake instead of a choice. Resetting to the new theme's own defaults keeps every theme looking like itself.
What it means in practice: don't sink real time into Advanced Design Configuration until you've settled on a theme. If you're still deciding between two or three, pick the one you want first, then tune. And if you do switch after tuning, the fix is quick, not painful. Reopen Advanced Design Configuration and pick your five settings again. It's dropdowns and swatches, not code. A couple minutes, not a rebuild.
One more honest note, for anyone managing a Cantrip site through an AI agent instead of the portal directly. The tool that changes themes has a flag for exactly this situation, apply_preset_defaults, and it defaults to true to match the portal's own behavior. Set it to false and you can switch themes while keeping your existing fonts and corners intact. The portal itself doesn't expose that choice today, so for now that's an agent-only move.