Font Loading Strategy
Load the custom fonts without invisible text, broken metrics, or a late reflow.
What it adds
A defined loading, fallback, and failure path for every custom font the interface depends on.
What your agent is told to do
5
What your agent is told to do
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1
List every font family, weight, and style the app actually renders, then check that list against what is being downloaded. Most apps ship weights nothing on the page uses.
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Choose a fallback whose metrics are adjusted to match the custom face, so the text laid out before the font arrives occupies close to the same space and the swap does not reflow the page.
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Preload only the faces needed for the first meaningful render. Preloading everything competes with the request for the content itself and delays the thing the user came for.
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Define what happens when the font never arrives: blocked network, a failed request, an unsupported format. The page must remain fully readable in the fallback indefinitely rather than showing invisible text.
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Do not solve a slow font by hiding text until it loads. Blank text on a working page is a worse failure than a brief change of typeface, and it is the failure users report as the site being broken.
Edge cases it handles
7
Edge cases it handles
7- The fallback must be metric-compatible or metric-adjusted, otherwise the swap shifts every line of text and the layout jumps after the page appeared finished.
- Preloading more than the critical faces steals bandwidth from the first render, so the preload list needs to be short and justified rather than generated from the whole family.
- Variable fonts change the calculation — one file may replace six, but only if the app actually uses the axes it carries, and language subsets need their own decision about which are fetched eagerly.
- A complete font failure must leave the page readable in the fallback rather than blank, which means the invisible-text period has to be bounded and short.
- Fonts loaded conditionally for a script the user's content requires must not arrive so late that the text has already been measured and laid out with a wrong-width fallback.
- Icon fonts fail differently from text fonts: an unloaded icon face renders as boxes or as unrelated characters, which is why icons belong in the Icon System rather than in a font.
- Reserving space for text that has not rendered is shared ground with Layout Shift Guard; this feature owns the font metrics and swap behaviour, and that feature owns detecting the movement when it happens anyway.
Definition of done
9
Definition of done
9- Text is readable throughout loading and never invisible for a prolonged period.
- Fallback metrics are adjusted so the swap produces no visible reflow.
- Only the faces required for first render are preloaded.
- Every weight and style downloaded is one the app actually renders.
- A total font failure leaves the interface fully usable in the fallback.
- Variable font axes and language subsets are loaded deliberately rather than wholesale.
- No icon or symbol rendering depends on a custom font loading successfully.
- The feature matches the existing design system.
- No existing functionality is broken.
Related features
Z-Index Registry
Z-Index Registry
Keep every stacking value in one file so nobody has to guess a bigger number.
What it does
A single source of named z-index tokens, with reserved ranges per layer and a check that blocks raw values.
How it works
- 1 Find every z-index in the codebase, including inline styles and values buried in third-party overrides, and list them with the component that owns each. The count is usually higher than anyone expects and several will be arbitrary large numbers.
- 2 Reserve a range for each layer rather than assigning single values, so a new dropdown can slot between existing ones without renumbering everything above it. Leave real gaps between ranges.
- 3 Name each token after the layer it belongs to and derive the ordering from Elevation Layer Map. That feature decides what covers what; this one holds the numbers and stops them being invented locally.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/z-index-registry
Spacing Scale
Spacing Scale
Reduce the app's spacing to a small set of steps that repeat across every surface.
What it does
A named spacing scale covering gaps, padding, and section rhythm, with every existing value in the app mapped onto it.
How it works
- 1 Collect every spacing value currently in the codebase and count how often each appears. The result is usually a handful of genuine intentions surrounded by dozens of near-misses that were nudged once and never revisited.
- 2 Define a scale that is fine at the small end, where control padding lives, and coarse at the large end, where section separation lives. A linear scale gives too many indistinguishable large steps and too few small ones.
- 3 Separate the tokens used inside a component from the ones used between components and between page sections, and name them so the difference is obvious. The same number serving both purposes means a change to button padding also changes the gap between sections.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/spacing-scale
Shadow Scale
Shadow Scale
Replace ad hoc shadows with a small set tied to what each surface actually is.
What it does
A fixed ladder of shadow tokens, each named for an elevation role rather than a blur radius.
How it works
- 1 Collect every shadow currently declared anywhere in the app and group them by what they sit on — a resting card, a hovered card, a dropdown, a dialog, a toast. Most apps have a dozen near-identical values that collapse into four or five roles.
- 2 Name each step for its role, not its appearance. A token called menu tells the next person which surfaces may use it; a token called shadow-md-2 does not.
- 3 Use a single light source for the whole scale, so offset, blur, and spread grow together as elevation rises. Two shadows lit from different directions on the same screen read as a rendering bug.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/shadow-scale
How it works
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1
Copy the link
Grab the Markdown instruction URL for this feature.
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2
Give it to your AI
Paste it into Claude Code, Cursor, v0, Lovable — whatever you build with.
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3
It inspects, then implements
Your agent reads your existing app first, then adds the feature to fit it.
Works with your stack
These instructions are written to adapt. They tell the agent to detect your framework, match your existing design system, and reuse what you already have — rather than assuming a particular stack.
Need it tighter than that? Customize the feature and tell it exactly what you're running.