feat(fonts): implement Phase 1 - Create Proxy API Client

- Created src/entities/Font/api/proxy/proxyFonts.ts
- Implemented fetchProxyFonts function with full pagination support
- Implemented fetchProxyFontById convenience function
- Added TypeScript interfaces: ProxyFontsParams, ProxyFontsResponse
- Added comprehensive JSDoc documentation
- Updated src/entities/Font/api/index.ts to export proxy API

Phase 1/7: Proxy API Integration for GlyphDiff

src/app/ui/Layout.svelte

@@ -41,7 +41,7 @@ let { children }: Props = $props();
     <header></header>
 
     <ScrollArea class="h-screen w-screen">
-        <main class="flex-1 w-full max-w-6xl mx-auto px-4 py-6 md:px-8 lg:py-10 relative">
+        <main class="flex-1 h-full w-full max-w-6xl mx-auto px-4 py-6 md:px-8 lg:py-10 relative">
             <TooltipProvider>
                 <TypographyMenu />
                 {@render children?.()}

src/entities/Font/api/index.ts

@@ -4,6 +4,17 @@
  * Exports API clients and normalization utilities
  */
 
+// Proxy API (PRIMARY - NEW)
+export {
+    fetchProxyFontById,
+    fetchProxyFonts,
+} from './proxy/proxyFonts';
+export type {
+    ProxyFontsParams,
+    ProxyFontsResponse,
+} from './proxy/proxyFonts';
+
+// Google Fonts API (DEPRECATED - kept for backward compatibility)
 export {
     fetchGoogleFontFamily,
     fetchGoogleFonts,
@@ -14,6 +25,7 @@ export type {
     GoogleFontsResponse,
 } from './google/googleFonts';
 
+// Fontshare API (DEPRECATED - kept for backward compatibility)
 export {
     fetchAllFontshareFonts,
     fetchFontshareFontBySlug,

src/entities/Font/api/proxy/proxyFonts.ts

@@ -0,0 +1,160 @@
+/**
+ * Proxy API client
+ *
+ * Handles API requests to GlyphDiff proxy API for fetching font metadata.
+ * Provides error handling, pagination support, and type-safe responses.
+ *
+ * Proxy API normalizes font data from Google Fonts and Fontshare into a single
+ * unified format, eliminating the need for client-side normalization.
+ *
+ * @see https://api.glyphdiff.com/api/v1/fonts
+ */
+
+import { api } from '$shared/api/api';
+import { buildQueryString } from '$shared/lib/utils';
+import type { QueryParams } from '$shared/lib/utils';
+import type { UnifiedFont } from '../../model/types';
+import type {
+    FontCategory,
+    FontSubset,
+} from '../../model/types';
+
+/**
+ * Proxy API base URL
+ */
+const PROXY_API_URL = 'https://api.glyphdiff.com/api/v1/fonts' as const;
+
+/**
+ * Proxy API parameters
+ *
+ * Maps directly to the proxy API query parameters
+ */
+export interface ProxyFontsParams extends QueryParams {
+    /**
+     * Font provider filter ("google" or "fontshare")
+     * Omit to fetch from both providers
+     */
+    provider?: 'google' | 'fontshare';
+
+    /**
+     * Font category filter
+     */
+    category?: FontCategory;
+
+    /**
+     * Character subset filter
+     */
+    subset?: FontSubset;
+
+    /**
+     * Search query (e.g., "roboto", "satoshi")
+     */
+    q?: string;
+
+    /**
+     * Sort order for results
+     * "name" - Alphabetical by font name
+     * "popularity" - Most popular first
+     * "lastModified" - Recently updated first
+     */
+    sort?: 'name' | 'popularity' | 'lastModified';
+
+    /**
+     * Number of items to return (pagination)
+     */
+    limit?: number;
+
+    /**
+     * Number of items to skip (pagination)
+     * Use for pagination: offset = (page - 1) * limit
+     */
+    offset?: number;
+}
+
+/**
+ * Proxy API response
+ *
+ * Includes pagination metadata alongside font data
+ */
+export interface ProxyFontsResponse {
+    /** Array of unified font objects */
+    fonts: UnifiedFont[];
+
+    /** Total number of fonts matching the query */
+    total: number;
+
+    /** Limit used for this request */
+    limit: number;
+
+    /** Offset used for this request */
+    offset: number;
+}
+
+/**
+ * Fetch fonts from proxy API
+ *
+ * @param params - Query parameters for filtering and pagination
+ * @returns Promise resolving to proxy API response
+ * @throws ApiError when request fails
+ *
+ * @example
+ * ```ts
+ * // Fetch all sans-serif fonts from Google
+ * const response = await fetchProxyFonts({
+ *     provider: 'google',
+ *     category: 'sans-serif',
+ *     limit: 50,
+ *     offset: 0
+ * });
+ *
+ * // Search fonts across all providers
+ * const searchResponse = await fetchProxyFonts({
+ *     q: 'roboto',
+ *     limit: 20
+ * });
+ *
+ * // Fetch fonts with pagination
+ * const page1 = await fetchProxyFonts({ limit: 50, offset: 0 });
+ * const page2 = await fetchProxyFonts({ limit: 50, offset: 50 });
+ * ```
+ */
+export async function fetchProxyFonts(
+    params: ProxyFontsParams = {},
+): Promise<ProxyFontsResponse> {
+    const queryString = buildQueryString(params);
+    const url = `${PROXY_API_URL}${queryString}`;
+
+    try {
+        const response = await api.get<ProxyFontsResponse>(url);
+        return response.data;
+    } catch (error) {
+        // Re-throw ApiError with context
+        if (error instanceof Error) {
+            throw error;
+        }
+        throw new Error(`Failed to fetch fonts from proxy API: ${String(error)}`);
+    }
+}
+
+/**
+ * Fetch font by ID
+ *
+ * Convenience function for fetching a single font by ID
+ * Note: This fetches a page and filters client-side, which is not ideal
+ * For production, consider adding a dedicated endpoint to the proxy API
+ *
+ * @param id - Font ID (family name for Google, slug for Fontshare)
+ * @returns Promise resolving to font or undefined
+ *
+ * @example
+ * ```ts
+ * const roboto = await fetchProxyFontById('Roboto');
+ * const satoshi = await fetchProxyFontById('satoshi');
+ * ```
+ */
+export async function fetchProxyFontById(
+    id: string,
+): Promise<UnifiedFont | undefined> {
+    const response = await fetchProxyFonts({ limit: 1000, q: id });
+    return response.fonts.find(font => font.id === id);
+}

src/routes/Page.svelte

@@ -3,8 +3,15 @@ import { appliedFontsManager } from '$entities/Font';
 import { displayedFontsStore } from '$features/DisplayFont';
 import FontDisplay from '$features/DisplayFont/ui/FontDisplay/FontDisplay.svelte';
 import { controlManager } from '$features/SetupFont';
+import { cn } from '$shared/shadcn/utils/shadcn-utils';
 import ComparisonSlider from '$widgets/ComparisonSlider/ui/ComparisonSlider/ComparisonSlider.svelte';
 import { FontSearch } from '$widgets/FontSearch';
+import { cubicOut } from 'svelte/easing';
+import { Spring } from 'svelte/motion';
+import type {
+    SlideParams,
+    TransitionConfig,
+} from 'svelte/transition';
 
 /**
  * Page Component
@@ -13,6 +20,9 @@ import { FontSearch } from '$widgets/FontSearch';
 let searchContainer: HTMLElement;
 
 let isExpanded = $state(false);
+let isOpen = $state(false);
+
+let isEmptyScreen = $derived(!displayedFontsStore.hasAnyFonts && !isExpanded && !isOpen);
 
 $effect(() => {
     appliedFontsManager.touch(
@@ -22,19 +32,63 @@ $effect(() => {
 </script>
 
 <!-- Font List -->
-<div class="p-2 will-change-[height]">
-    <div bind:this={searchContainer}>
-        <FontSearch bind:showFilters={isExpanded} />
+<div class="p-2 h-full flex flex-col gap-3 overflow-hidden">
+    {#key isEmptyScreen}
+        <div
+            class={cn(
+                'flex flex-col transition-all duration-700 ease-[cubic-bezier(0.23,1,0.32,1)] mx-40',
+                'will-change-[flex-grow] transform-gpu',
+                isEmptyScreen
+                    ? 'grow justify-center'
+                    : 'animate-search',
+            )}
+        >
+            <div
+                class={cn(
+                    'transition-transform duration-700 ease-[cubic-bezier(0.23,1,0.32,1)]',
+                )}
+            >
+                <FontSearch bind:showFilters={isExpanded} bind:isOpen />
+            </div>
+        </div>
+    {/key}
+
+    <div class="my-2 mx-10">
+        <ComparisonSlider />
     </div>
 
-    <ComparisonSlider />
-
-    <div class="will-change-tranform transition-transform content">
+    <div class="will-change-tranform transition-transform content my-2">
         <FontDisplay />
     </div>
 </div>
 
 <style>
+@keyframes search {
+        0% {
+            opacity: 1;
+            transform: scale(1);
+            flex-grow: 1;
+            justify-content: center;
+        }
+        15% {
+            opacity: 0.5;
+            transform: scale(0.95);
+        }
+        30% {
+            opacity: 0;
+        }
+        100% {
+            opacity: 1;
+            transform: scale(1);
+            flex-grow: 0;
+            justify-content: flex-start;
+        }
+    }
+
+    .animate-search {
+        animation: search 0.5s cubic-bezier(0.165, 0.84, 0.44, 1) forwards;
+    }
+
 .content {
         /* Tells the browser to skip rendering off-screen content */
         content-visibility: auto;
@@ -44,4 +98,10 @@ $effect(() => {
         -webkit-font-smoothing: antialiased;
         -moz-osx-font-smoothing: grayscale;
 }
+
+.will-change-[height] {
+    will-change: flex-grow, padding;
+    /* Forces GPU acceleration for the layout shift */
+    transform: translateZ(0);
+}
 </style>

src/shared/ui/SearchBar/SearchBar.svelte

@@ -17,30 +17,46 @@ import { useId } from 'bits-ui';
 import type { Snippet } from 'svelte';
 
 interface Props {
-    /** Unique identifier for the input element */
+    /**
+     * Unique identifier for the input element
+     */
     id?: string;
-    /** Current search value (bindable) */
+    /**
+     * Current search value (bindable)
+     */
     value: string;
-    /** Additional CSS classes for the container */
+    /**
+     * Whether popover is open (bindable)
+     */
+    isOpen?: boolean;
+    /**
+     * Additional CSS classes for the container
+     */
     class?: string;
-    /** Placeholder text for the input */
+    /**
+     * Placeholder text for the input
+     */
     placeholder?: string;
-    /** Optional label displayed above the input */
+    /**
+     * Optional label displayed above the input
+     */
     label?: string;
-    /** Content to render inside the popover (receives unique content ID) */
+    /**
+     * Content to render inside the popover (receives unique content ID)
+     */
     children: Snippet<[{ id: string }]> | undefined;
 }
 
 let {
     id = 'search-bar',
-    value = $bindable(),
+    value = $bindable(''),
+    isOpen = $bindable(false),
     class: className,
     placeholder,
     label,
     children,
 }: Props = $props();
 
-let open = $state(false);
 let triggerRef = $state<HTMLInputElement>(null!);
 // svelte-ignore state_referenced_locally
 const contentId = useId(id);
@@ -52,11 +68,11 @@ function handleKeyDown(event: KeyboardEvent) {
 }
 
 function handleInputClick() {
-    open = true;
+    isOpen = true;
 }
 </script>
 
-<PopoverRoot bind:open>
+<PopoverRoot bind:open={isOpen}>
     <PopoverTrigger bind:ref={triggerRef}>
         {#snippet child({ props })}
             {@const { onclick, ...rest } = props}

src/widgets/ComparisonSlider/ui/ComparisonSlider/FontShifter.svelte

@@ -0,0 +1,52 @@
+<script lang="ts">
+import { cn } from '$shared/shadcn/utils/shadcn-utils';
+
+interface Props {
+    text: string;
+    fontName: string;
+    isAnimating: boolean;
+    onAnimationComplete?: () => void;
+}
+
+let { text, fontName, isAnimating, onAnimationComplete }: Props = $props();
+
+// Split text into characters, preserving spaces
+const chars = $derived(text.split('').map(c => c === ' ' ? '\u00A0' : c));
+
+let completedCount = 0;
+
+function handleTransitionEnd() {
+    completedCount++;
+    if (completedCount === chars.length) {
+        onAnimationComplete?.();
+        completedCount = 0;
+    }
+}
+</script>
+
+<div class="relative inline-flex flex-wrap leading-tight">
+    {#each chars as char, i}
+        <span
+            class={cn(
+                'inline-block transition-all duration-500 ease-[cubic-bezier(0.34,1.56,0.64,1)]',
+                isAnimating ? 'opacity-0 -translate-y-4 rotate-x-90' : 'opacity-100 translate-y-0 rotate-x-0',
+            )}
+            style:font-family={fontName}
+            style:transition-delay="{i * 25}ms"
+            ontransitionend={i === chars.length - 1 ? handleTransitionEnd : null}
+        >
+            {char}
+        </span>
+    {/each}
+</div>
+
+<style>
+/* Necessary for the "Flip" feel */
+div {
+	perspective: 1000px;
+}
+span {
+	transform-style: preserve-3d;
+	backface-visibility: hidden;
+}
+</style>

src/widgets/FontSearch/ui/FontSearch/FontSearch.svelte

@@ -27,9 +27,10 @@ import { type SlideParams } from 'svelte/transition';
 
 interface Props {
     showFilters?: boolean;
+    isOpen?: boolean;
 }
 
-let { showFilters = $bindable(false) }: Props = $props();
+let { showFilters = $bindable(false), isOpen = $bindable(false) }: Props = $props();
 
 onMount(() => {
     /**
@@ -68,6 +69,7 @@ function toggleFilters() {
         class="w-full"
         placeholder="Search fonts by name..."
         bind:value={filterManager.queryValue}
+        bind:isOpen
     >
         <SuggestedFonts />
     </SearchBar>

src/widgets/TypographySettings/ui/TypographyMenu.svelte

@@ -24,7 +24,7 @@ const [send, receive] = crossfade({
 
 {#if displayedFontsStore.hasAnyFonts}
     <div
-        class="w-auto fixed bottom-5 left-1/2 translate-x-[-50%] max-w-max z-10"
+        class="w-auto fixed bottom-5 inset-x-0 max-screen z-10 flex justify-center"
         in:receive={{ key: 'panel' }}
         out:send={{ key: 'panel' }}
     >