src/app/styles/app.css

@@ -1,5 +1,6 @@
 @import "tailwindcss";
 @import "tw-animate-css";
+@import "./fonts.css";
 
 @variant dark (&:where(.dark, .dark *));
 
@@ -216,9 +217,7 @@
   /* Monospace label tracking — used in Loader and Footnote */
   --tracking-wider-mono: 0.2em;
 
-  /* ============================================
+  /* Shadow tokens */
-     SHADOW TOKENS
-     ============================================ */
 
   /* Default resting shadow — equivalent to Tailwind's shadow-sm. Used on
      buttons, sliders, popover triggers in non-floating state. */
@@ -245,9 +244,7 @@
   /* Drawer / overlay shadow — full-strength shadow-2xl. */
   --shadow-overlay: 0 25px 50px -12px rgb(0 0 0 / 0.25);
 
-  /* ============================================
+  /* Motion tokens */
-     MOTION TOKENS
-     ============================================ */
 
   --duration-fast: 150ms;
   --duration-normal: 200ms;
@@ -274,7 +271,7 @@
 
   body {
     @apply bg-background text-foreground;
-    font-family: "Karla", system-ui, -apple-system, "Segoe UI", Inter, Roboto, Arial, sans-serif;
+    font-family: var(--font-secondary);
     font-optical-sizing: auto;
   }
 
@@ -325,9 +322,7 @@
   }
 }
 
-/* ============================================
+/* Design-system utilities.
-   DESIGN-SYSTEM UTILITIES
-   ============================================
    Defined via `@utility` (Tailwind v4) so they integrate with the variant
    system (`hover:`, `dark:`, breakpoints) and don't rely on `@apply`
    chains. Colors reference the mode-switching semantic vars defined in
@@ -362,7 +357,7 @@
   }
 }
 
-/* ── Surface utilities ────────────────────────────────────────── */
+/* Surface utilities */
 
 @utility surface-canvas {
   background-color: var(--color-surface);
@@ -391,7 +386,7 @@
   border: 1px solid var(--color-border-subtle);
 }
 
-/* ── Shape / layout ───────────────────────────────────────────── */
+/* Shape / layout */
 
 @utility flex-center {
   display: flex;
@@ -422,7 +417,7 @@
   background-size: 10px 10px;
 }
 
-/* ── Typography ───────────────────────────────────────────────── */
+/* Typography */
 
 @utility text-label-mono {
   font-family: var(--font-primary);
@@ -431,7 +426,7 @@
   text-transform: uppercase;
 }
 
-/* Global utility - useful across your app */
+/* Honor prefers-reduced-motion: collapse animation and transition timing. */
 @media (prefers-reduced-motion: reduce) {
     * {
         animation-duration: 0.01ms !important;
@@ -440,12 +435,12 @@
     }
 }
 
-/* Performance optimization for collapsible elements */
+/* Hint the upcoming height animation on open collapsibles. */
 [data-state="open"] {
     will-change: height;
 }
 
-/* Smooth focus transitions - good globally */
+/* Transition siblings of a focus-visible peer. */
 .peer:focus-visible ~ * {
     transition: all 150ms cubic-bezier(0.4, 0, 0.2, 1);
 }
@@ -472,11 +467,9 @@
     animation: nudge 10s ease-in-out infinite;
 }
 
-/* ============================================
+/* Scrollbar styling */
-   SCROLLBAR STYLES
-   ============================================ */
 
-/* ---- Modern API: color + width (Chrome 121+, FF 64+) ---- */
+/* Standard API: color + width (Chrome 121+, Firefox 64+). */
 @supports (scrollbar-width: auto) {
     * {
         scrollbar-width: thin;
@@ -488,8 +481,8 @@
     }
 }
 
-/* ---- Webkit layer: runs ON TOP in Chrome, standalone in old Safari ---- */
+/* WebKit fallback: applies on top of the standard API in Chrome, standalone in
-/* Handles things scrollbar-width can't: hiding buttons, exact sizing    */
+   older Safari. Covers what scrollbar-width can't — hiding buttons, exact sizing. */
 @supports selector(::-webkit-scrollbar) {
     ::-webkit-scrollbar {
         width: 6px;
@@ -497,7 +490,7 @@
     }
 
     ::-webkit-scrollbar-button {
-        display: none;  /* kills arrows */
+        display: none; /* hide scrollbar buttons */
     }
 
     ::-webkit-scrollbar-track {

src/app/styles/fonts.css

@@ -0,0 +1,78 @@
+/*
+    Self-hosted interface fonts (latin subset only).
+    Vendored from @fontsource — see docs/interface-font-selfhost-benchmark.md.
+    Variable faces (Inter, Space Grotesk) keep their wght axis; Inter also keeps opsz.
+    url()s are resolved + content-hashed by Vite at build → immutable long-cache.
+*/
+
+/* Inter — variable wght + opsz, the body/secondary UI font (--font-secondary) */
+@font-face {
+    font-family: 'Inter';
+    font-style: normal;
+    font-display: swap;
+    font-weight: 100 900;
+    src: url('../assets/fonts/inter-latin-opsz-normal.woff2') format('woff2');
+    unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
+}
+@font-face {
+    font-family: 'Inter';
+    font-style: italic;
+    font-display: swap;
+    font-weight: 100 900;
+    src: url('../assets/fonts/inter-latin-opsz-italic.woff2') format('woff2');
+    unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
+}
+
+/* Space Grotesk — variable wght, the primary/display UI font (--font-primary) */
+@font-face {
+    font-family: 'Space Grotesk';
+    font-style: normal;
+    font-display: swap;
+    font-weight: 300 700;
+    src: url('../assets/fonts/space-grotesk-latin-wght-normal.woff2') format('woff2');
+    unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
+}
+
+/* Space Mono — static 400/700 × roman/italic (--font-mono) */
+@font-face {
+    font-family: 'Space Mono';
+    font-style: normal;
+    font-display: swap;
+    font-weight: 400;
+    src: url('../assets/fonts/space-mono-latin-400-normal.woff2') format('woff2');
+    unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
+}
+@font-face {
+    font-family: 'Space Mono';
+    font-style: italic;
+    font-display: swap;
+    font-weight: 400;
+    src: url('../assets/fonts/space-mono-latin-400-italic.woff2') format('woff2');
+    unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
+}
+@font-face {
+    font-family: 'Space Mono';
+    font-style: normal;
+    font-display: swap;
+    font-weight: 700;
+    src: url('../assets/fonts/space-mono-latin-700-normal.woff2') format('woff2');
+    unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
+}
+@font-face {
+    font-family: 'Space Mono';
+    font-style: italic;
+    font-display: swap;
+    font-weight: 700;
+    src: url('../assets/fonts/space-mono-latin-700-italic.woff2') format('woff2');
+    unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
+}
+
+/* Syne — static 800, the logo font (--font-logo) */
+@font-face {
+    font-family: 'Syne';
+    font-style: normal;
+    font-display: swap;
+    font-weight: 800;
+    src: url('../assets/fonts/syne-latin-800-normal.woff2') format('woff2');
+    unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
+}

src/app/types/ambient.d.ts

@@ -38,6 +38,11 @@ declare module '*.jpg' {
 
 declare module '*.css';
 
+declare module '*.woff2?url' {
+    const content: string;
+    export default content;
+}
+
 /// <reference types="vite/client" />
 
 interface ImportMetaEnv {

src/app/ui/Layout.svelte

@@ -9,6 +9,14 @@ import { ResponsiveProvider } from '$shared/lib';
 import { cn } from '$shared/lib';
 import { Footer } from '$widgets/Footer';
 
+/*
+    Preload the two render-critical interface faces (primary + secondary).
+    `?url` resolves to the content-hashed path Vite emits, so the binary is
+    fetched immediately rather than waiting for CSS @font-face discovery.
+*/
+import interWoff2 from '../assets/fonts/inter-latin-opsz-normal.woff2?url';
+import spaceGroteskWoff2 from '../assets/fonts/space-grotesk-latin-wght-normal.woff2?url';
+
 import {
     type Snippet,
     onDestroy,
@@ -33,36 +41,21 @@ onDestroy(() => themeManager.destroy());
 <svelte:head>
     <link rel="icon" href={G} type="image/svg+xml" />
 
-    <link rel="preconnect" href="https://api.fontshare.com" />
+    <!-- Self-hosted interface fonts (see src/app/styles/fonts/fonts.css). Preload the two critical faces. -->
     <link
-        rel="preconnect"
+        rel="preload"
-        href="https://cdn.fontshare.com"
+        as="font"
-        crossorigin="anonymous"
+        type="font/woff2"
-    />
+        href={interWoff2}
-
-    <link rel="preconnect" href="https://fonts.googleapis.com" />
-    <link
-        rel="preconnect"
-        href="https://fonts.gstatic.com"
         crossorigin="anonymous"
     />
     <link
         rel="preload"
-        as="style"
+        as="font"
-        href="https://fonts.googleapis.com/css2?family=Inter:ital,opsz,wght@0,14..32,100..900;1,14..32,100..900&family=Space+Grotesk:wght@300..700&family=Space+Mono:ital,wght@0,400;0,700;1,400;1,700&family=Syne:wght@800&display=swap"
+        type="font/woff2"
+        href={spaceGroteskWoff2}
+        crossorigin="anonymous"
     />
-    <link
-        rel="stylesheet"
-        href="https://fonts.googleapis.com/css2?family=Inter:ital,opsz,wght@0,14..32,100..900;1,14..32,100..900&family=Space+Grotesk:wght@300..700&family=Space+Mono:ital,wght@0,400;0,700;1,400;1,700&family=Syne:wght@800&display=swap"
-        media="print"
-        onload={(e => ((e.currentTarget as HTMLLinkElement).media = 'all'))}
-    />
-    <noscript>
-        <link
-            rel="stylesheet"
-            href="https://fonts.googleapis.com/css2?family=Inter:ital,opsz,wght@0,14..32,100..900;1,14..32,100..900&family=Space+Grotesk:wght@300..700&family=Space+Mono:ital,wght@0,400;0,700;1,400;1,700&family=Syne:wght@800&display=swap"
-        />
-    </noscript>
     <title>GlyphDiff | Typography & Typefaces</title>
     <meta
         name="description"