src/app/ui/Layout.svelte

@@ -12,6 +12,7 @@
  */
 import { BreadcrumbHeader } from '$entities/Breadcrumb';
 import favicon from '$shared/assets/favicon.svg';
+import { ResponsiveProvider } from '$shared/lib';
 import { ScrollArea } from '$shared/shadcn/ui/scroll-area';
 import { Provider as TooltipProvider } from '$shared/shadcn/ui/tooltip';
 import { TypographyMenu } from '$widgets/TypographySettings';
@@ -42,6 +43,7 @@ let { children }: Props = $props();
     >
 </svelte:head>
 
+<ResponsiveProvider>
     <div id="app-root" class="min-h-screen flex flex-col bg-background">
         <header>
             <BreadcrumbHeader />
@@ -57,3 +59,4 @@ let { children }: Props = $props();
         <!-- </ScrollArea> -->
         <footer></footer>
     </div>
+</ResponsiveProvider>

src/features/SetupFont/lib/controlManager/controlManager.svelte.ts

@@ -15,6 +15,7 @@ export interface Control {
 
 export class TypographyControlManager {
     #controls = new SvelteMap<string, Control>();
+    #sizeMultiplier = $state(1);
 
     constructor(configs: ControlModel[]) {
         configs.forEach(({ id, increaseLabel, decreaseLabel, controlLabel, ...config }) => {
@@ -37,7 +38,8 @@ export class TypographyControlManager {
     }
 
     get size() {
-        return this.#controls.get('font_size')?.instance.value;
+        const size = this.#controls.get('font_size')?.instance.value;
+        return size === undefined ? undefined : size * this.#sizeMultiplier;
     }
 
     get height() {
@@ -47,6 +49,10 @@ export class TypographyControlManager {
     get spacing() {
         return this.#controls.get('letter_spacing')?.instance.value;
     }
+
+    set multiplier(value: number) {
+        this.#sizeMultiplier = value;
+    }
 }
 
 /**

src/features/SetupFont/ui/SetupFontMenu.svelte

@@ -3,8 +3,32 @@
     Contains controls for setting up font properties.
 -->
 <script lang="ts">
+import type { ResponsiveManager } from '$shared/lib';
 import { ComboControl } from '$shared/ui';
+import { getContext } from 'svelte';
 import { controlManager } from '../model';
+const responsive = getContext<ResponsiveManager>('responsive');
+
+$effect(() => {
+    if (!responsive) {
+        return;
+    }
+
+    switch (true) {
+        case responsive.isMobile:
+            controlManager.multiplier = 0.5;
+            break;
+        case responsive.isTablet:
+            controlManager.multiplier = 0.75;
+            break;
+        case responsive.isDesktop:
+            controlManager.multiplier = 1;
+            break;
+        default:
+            controlManager.multiplier = 1;
+            break;
+    }
+});
 </script>
 
 <div class="py-2 px-10 flex flex-row items-center gap-2">

src/shared/lib/helpers/createResponsiveManager/createResponsiveManager.svelte.ts

@@ -0,0 +1,231 @@
+// $shared/lib/createResponsiveManager.svelte.ts
+
+/**
+ * Breakpoint definitions following common device sizes
+ * Customize these values to match your design system
+ */
+export interface Breakpoints {
+    /** Mobile devices (portrait phones) */
+    mobile: number;
+    /** Tablet portrait */
+    tabletPortrait: number;
+    /** Tablet landscape */
+    tablet: number;
+    /** Desktop */
+    desktop: number;
+    /** Large desktop */
+    desktopLarge: number;
+}
+
+/**
+ * Default breakpoints (matches common Tailwind-like breakpoints)
+ */
+const DEFAULT_BREAKPOINTS: Breakpoints = {
+    mobile: 640, // sm
+    tabletPortrait: 768, // md
+    tablet: 1024, // lg
+    desktop: 1280, // xl
+    desktopLarge: 1536, // 2xl
+};
+
+/**
+ * Orientation type
+ */
+export type Orientation = 'portrait' | 'landscape';
+
+/**
+ * Creates a reactive responsive manager that tracks viewport size and breakpoints.
+ *
+ * Provides reactive getters for:
+ * - Current breakpoint detection (isMobile, isTablet, etc.)
+ * - Viewport dimensions (width, height)
+ * - Device orientation (portrait/landscape)
+ * - Custom breakpoint matching
+ *
+ * @param customBreakpoints - Optional custom breakpoint values
+ * @returns Responsive manager instance with reactive properties
+ *
+ * @example
+ * ```svelte
+ * <script lang="ts">
+ *   const responsive = createResponsiveManager();
+ * </script>
+ *
+ * {#if responsive.isMobile}
+ *   <MobileNav />
+ * {:else if responsive.isTablet}
+ *   <TabletNav />
+ * {:else}
+ *   <DesktopNav />
+ * {/if}
+ *
+ * <p>Width: {responsive.width}px</p>
+ * <p>Orientation: {responsive.orientation}</p>
+ * ```
+ */
+export function createResponsiveManager(customBreakpoints?: Partial<Breakpoints>) {
+    const breakpoints: Breakpoints = {
+        ...DEFAULT_BREAKPOINTS,
+        ...customBreakpoints,
+    };
+
+    // Reactive state
+    let width = $state(typeof window !== 'undefined' ? window.innerWidth : 0);
+    let height = $state(typeof window !== 'undefined' ? window.innerHeight : 0);
+
+    // Derived breakpoint states
+    const isMobile = $derived(width < breakpoints.mobile);
+    const isTabletPortrait = $derived(
+        width >= breakpoints.mobile && width < breakpoints.tabletPortrait,
+    );
+    const isTablet = $derived(
+        width >= breakpoints.tabletPortrait && width < breakpoints.desktop,
+    );
+    const isDesktop = $derived(
+        width >= breakpoints.desktop && width < breakpoints.desktopLarge,
+    );
+    const isDesktopLarge = $derived(width >= breakpoints.desktopLarge);
+
+    // Convenience groupings
+    const isMobileOrTablet = $derived(width < breakpoints.desktop);
+    const isTabletOrDesktop = $derived(width >= breakpoints.tabletPortrait);
+
+    // Orientation
+    const orientation = $derived<Orientation>(height > width ? 'portrait' : 'landscape');
+    const isPortrait = $derived(orientation === 'portrait');
+    const isLandscape = $derived(orientation === 'landscape');
+
+    // Touch device detection (best effort)
+    const isTouchDevice = $derived(
+        typeof window !== 'undefined'
+            && ('ontouchstart' in window || navigator.maxTouchPoints > 0),
+    );
+
+    /**
+     * Initialize responsive tracking
+     * Call this in an $effect or component mount
+     */
+    function init() {
+        if (typeof window === 'undefined') return;
+
+        const handleResize = () => {
+            width = window.innerWidth;
+            height = window.innerHeight;
+        };
+
+        // Use ResizeObserver for more accurate tracking
+        const resizeObserver = new ResizeObserver(handleResize);
+        resizeObserver.observe(document.documentElement);
+
+        // Fallback to window resize event
+        window.addEventListener('resize', handleResize, { passive: true });
+
+        // Initial measurement
+        handleResize();
+
+        return () => {
+            resizeObserver.disconnect();
+            window.removeEventListener('resize', handleResize);
+        };
+    }
+
+    /**
+     * Check if current width matches a custom breakpoint
+     * @param min - Minimum width (inclusive)
+     * @param max - Maximum width (exclusive)
+     */
+    function matches(min: number, max?: number): boolean {
+        if (max !== undefined) {
+            return width >= min && width < max;
+        }
+        return width >= min;
+    }
+
+    /**
+     * Get the current breakpoint name
+     */
+    const currentBreakpoint = $derived<keyof Breakpoints | 'xs'>(
+        (() => {
+            if (isMobile) return 'mobile';
+            if (isTabletPortrait) return 'tabletPortrait';
+            if (isTablet) return 'tablet';
+            if (isDesktop) return 'desktop';
+            if (isDesktopLarge) return 'desktopLarge';
+            return 'xs'; // Fallback for very small screens
+        })(),
+    );
+
+    return {
+        // Dimensions
+        get width() {
+            return width;
+        },
+        get height() {
+            return height;
+        },
+
+        // Standard breakpoints
+        get isMobile() {
+            return isMobile;
+        },
+        get isTabletPortrait() {
+            return isTabletPortrait;
+        },
+        get isTablet() {
+            return isTablet;
+        },
+        get isDesktop() {
+            return isDesktop;
+        },
+        get isDesktopLarge() {
+            return isDesktopLarge;
+        },
+
+        // Convenience groupings
+        get isMobileOrTablet() {
+            return isMobileOrTablet;
+        },
+        get isTabletOrDesktop() {
+            return isTabletOrDesktop;
+        },
+
+        // Orientation
+        get orientation() {
+            return orientation;
+        },
+        get isPortrait() {
+            return isPortrait;
+        },
+        get isLandscape() {
+            return isLandscape;
+        },
+
+        // Device capabilities
+        get isTouchDevice() {
+            return isTouchDevice;
+        },
+
+        // Current breakpoint
+        get currentBreakpoint() {
+            return currentBreakpoint;
+        },
+
+        // Methods
+        init,
+        matches,
+
+        // Breakpoint values (for custom logic)
+        breakpoints,
+    };
+}
+
+export const responsiveManager = createResponsiveManager();
+
+if (typeof window !== 'undefined') {
+    responsiveManager.init();
+}
+
+/**
+ * Type for the responsive manager instance
+ */
+export type ResponsiveManager = ReturnType<typeof createResponsiveManager>;

src/shared/lib/helpers/index.ts

@@ -33,3 +33,9 @@ export {
 } from './createCharacterComparison/createCharacterComparison.svelte';
 
 export { createPersistentStore } from './createPersistentStore/createPersistentStore.svelte';
+
+export {
+    createResponsiveManager,
+    type ResponsiveManager,
+    responsiveManager,
+} from './createResponsiveManager/createResponsiveManager.svelte';

src/shared/lib/index.ts

@@ -6,6 +6,7 @@ export {
     createEntityStore,
     createFilter,
     createPersistentStore,
+    createResponsiveManager,
     createTypographyControl,
     createVirtualizer,
     type Entity,
@@ -14,6 +15,8 @@ export {
     type FilterModel,
     type LineData,
     type Property,
+    type ResponsiveManager,
+    responsiveManager,
     type TypographyControl,
     type VirtualItem,
     type Virtualizer,
@@ -23,3 +26,5 @@ export {
 export { splitArray } from './utils';
 
 export { springySlideFade } from './transitions';
+
+export { ResponsiveProvider } from './providers';

src/shared/lib/providers/ResponsiveProvider/ResponsiveProvider.svelte

@@ -0,0 +1,30 @@
+<!--
+    Component: ResponsiveProvider
+    Provides a responsive manager to all children
+-->
+<script lang="ts">
+import {
+    type ResponsiveManager,
+    createResponsiveManager,
+} from '$shared/lib/helpers';
+import { setContext } from 'svelte';
+import type { Snippet } from 'svelte';
+
+interface Props {
+    children: Snippet;
+}
+
+let { children }: Props = $props();
+
+const responsive = createResponsiveManager();
+
+// Initialize and cleanup
+$effect(() => {
+    return responsive.init();
+});
+
+// Provide to all children
+setContext('responsive', responsive);
+</script>
+
+{@render children()}

src/shared/lib/providers/index.ts

@@ -0,0 +1 @@
+export { default as ResponsiveProvider } from './ResponsiveProvider/ResponsiveProvider.svelte';