Picture a small law firm building a site with a neural network, without rushing. The homepage was generated in March, services in April, the team section in May. Each prompt was detailed, mentioned brand blue and a “strict but friendly” style. Every page looked fine on its own.
Then they opened them back to back. Blue is blue everywhere, but homepage buttons are rounded, service buttons square, and the team section has no buttons at all—just links. Headlines differ in size, cards have different padding, icons come from three sets. Like a family album where everyone is related but nobody looks alike.
Why the model draws a slightly different site each time
Each run is a new decision. The model sees the prompt, not your page history, unless you feed it in. “Strict but friendly” is a direction, not a spec, and hundreds of variants fit that direction. It picks one; a month later it will likely pick another.
Tilda’s DESIGN.md docs say it plainly: if no style is chosen for a Vibe block, the block is created in whatever style the AI model picks. That is honest for any generation. Without fixed rules, a single look does not appear on its own—you keep guessing.
What to lock down besides colors
Palette is the most visible and easiest part. Two or three colors feel like “the style” is done. In practice, character hangs on what prompts rarely mention: type scale for headings and body, spacing between blocks, button shape and states, how cards, forms, and lists are built.
I treat a design system as repeatable decisions. Which button is primary, which secondary. What a service card looks like and what it must include—title, short text, price or link. What happens on mobile. How form labels sound. The more answers are fixed upfront, the less improvisation on the next generated page—and fewer surprises when you flip through pages in a row.
Long copy is the best stress test
Mocks use easy text. One-line titles, two-line blurbs, three tidy cards. A law firm’s real copy is different: “Commercial real estate and lease transaction support” in a card built for “Consultations” breaks height and grid rhythm.
A solid system describes awkward cases: long titles, empty fields, three lines instead of one, narrow screens. Without those rules, the model improvises per case. On one page a long title shrinks, on another wraps, on a third ellipsizes. Each choice is fine alone. Together they make that family album.
What DESIGN.md gives you—and what it does not
For Vibe blocks Tilda has a dedicated answer. Per the docs, DESIGN.md describes design—colors, typography, components—and the AI Agent reads it and builds blocks in that style. You pick from the library, browse by category, or add your own; at generation the style shows up in Context. Only one DESIGN.md style at a time.
It is useful: the model gets shared context and runs stop starting from zero. The docs describe context for generation, not a guarantee every element matches the file, and not usability or accessibility checks. Remember DESIGN.md lives inside Vibe blocks, and Vibe blocks have their own maintenance: code, a Content panel that varies by block, edits that can hit similar elements.
One site, not a pile of pages
When pages multiply over time, set the shared look before the first generation: project styles, card structure, text rules. Then a page added six months later still feels like the same site.
Where the design system lives on standard blocks
Standard Tilda blocks have had a home for shared rules longer than any neural net. Font docs: family, size, weight, and color for headings and text sit in site settings and apply to all standard blocks unless a block overrides. Under Colors and styles you can define color, type, and button styles; type styles can set sizes per breakpoint. You can export and import styles to another project.
I prefer this flow: AI helps find a visual direction and a prototype; then rules move into project styles and pages are built on those. The prototype stays a draft; the site gets one place where its character lives. Change a button style once and every button updates—no page tour.
The law firm need not redo everything. Pick the page you like most, describe its decisions in words and styles, and align the rest. The album will not get dull—relatives will finally recognize each other.