feat(ComparisonSlider): add perspective manager and tweak styles

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

@@ -8,17 +8,23 @@
     - Character-level morphing: Font changes exactly when the slider passes the character's global position.
     - Responsive layout with Tailwind breakpoints for font sizing.
     - Performance optimized using offscreen canvas for measurements and transform-based animations.
+
+    Modes:
+    - Slider mode: Text centered in 1st plan, controls hidden
+    - Settings mode: Text moves to left (2nd plan), controls appear on right (1st plan)
 -->
 <script lang="ts">
 import {
+    type CharacterComparison,
+    type LineData,
+    type ResponsiveManager,
     createCharacterComparison,
-    createTypographyControl,
+    createPerspectiveManager,
 } from '$shared/lib';
-import type {
-    LineData,
-    ResponsiveManager,
-} from '$shared/lib';
-import { Loader } from '$shared/ui';
+import {
+    Loader,
+    PerspectivePlan,
+} from '$shared/ui';
 import { comparisonStore } from '$widgets/ComparisonSlider/model';
 import { getContext } from 'svelte';
 import { Spring } from 'svelte/motion';
@@ -31,10 +37,11 @@ import SliderLine from './components/SliderLine.svelte';
 const fontA = $derived(comparisonStore.fontA);
 const fontB = $derived(comparisonStore.fontB);
 
-const isLoading = $derived(comparisonStore.isLoading || !comparisonStore.isReady);
+const isLoading = $derived(
+    comparisonStore.isLoading || !comparisonStore.isReady,
+);
 
 let container = $state<HTMLElement>();
-let typographyControls = $state<HTMLDivElement | null>(null);
 let measureCanvas = $state<HTMLCanvasElement>();
 let isDragging = $state(false);
 const typography = $derived(comparisonStore.typography);
@@ -45,7 +52,7 @@ const responsive = getContext<ResponsiveManager>('responsive');
  * Encapsulated helper for text splitting, measuring, and character proximity calculations.
  * Manages line breaking and character state based on fonts and container dimensions.
  */
-const charComparison = createCharacterComparison(
+const charComparison: CharacterComparison = createCharacterComparison(
     () => comparisonStore.text,
     () => fontA,
     () => fontB,
@@ -53,6 +60,22 @@ const charComparison = createCharacterComparison(
     () => typography.renderedSize,
 );
 
+/**
+ * Perspective manager for back/front state toggling:
+ * - Front (slider mode): Text fully visible, interactive
+ * - Back (settings mode): Text blurred, scaled down, shifted left, controls visible
+ *
+ * Uses simple boolean flag for smooth transitions between states.
+ */
+const perspective = createPerspectiveManager({
+    parallaxIntensity: 0, // Disabled to not interfere with slider
+    horizontalOffset: 0, // Text shifts left when in back position
+    scaleStep: 0.5,
+    blurStep: 2,
+    depthStep: 100,
+    opacityStep: 0.3,
+});
+
 let lineElements = $state<(HTMLElement | undefined)[]>([]);
 
 /** Physics-based spring for smooth handle movement */
@@ -64,7 +87,10 @@ const sliderPos = $derived(sliderSpring.current);
 
 /** Updates spring target based on pointer position */
 function handleMove(e: PointerEvent) {
-    if (!isDragging || !container) return;
+    if (!isDragging || !container) {
+        return;
+    }
+
     const rect = container.getBoundingClientRect();
     const x = Math.max(0, Math.min(e.clientX - rect.left, rect.width));
     const percentage = (x / rect.width) * 100;
@@ -72,18 +98,15 @@ function handleMove(e: PointerEvent) {
 }
 
 function startDragging(e: PointerEvent) {
-    if (
-        e.target === typographyControls
-        || typographyControls?.contains(e.target as Node)
-    ) {
-        e.stopPropagation();
-        return;
-    }
     e.preventDefault();
     isDragging = true;
     handleMove(e);
 }
 
+function togglePerspective() {
+    perspective.toggle();
+}
+
 /**
  * Sets the multiplier for slider font size based on the current responsive state
  */
@@ -146,28 +169,28 @@ $effect(() => {
     window.addEventListener('resize', handleResize);
     return () => window.removeEventListener('resize', handleResize);
 });
+
+const isInSettingsMode = $derived(perspective.isBack);
 </script>
 
 {#snippet renderLine(line: LineData, index: number)}
+    {@const pos = sliderPos}
+    {@const element = lineElements[index]}
     <div
         bind:this={lineElements[index]}
         class="relative flex w-full justify-center items-center whitespace-nowrap"
         style:height={`${typography.height}em`}
         style:line-height={`${typography.height}em`}
     >
-        {#each line.text.split('') as char, charIndex}
-            {@const { proximity, isPast } = charComparison.getCharState(charIndex, sliderPos, lineElements[index], container)}
+        {#each line.text.split('') as char, index}
+            {@const { proximity, isPast } = charComparison.getCharState(index, pos, element, container)}
             <!--
                 Single Character Span
                 - Font Family switches based on `isPast`
                 - Transitions/Transforms provide the "morph" feel
             -->
             {#if fontA && fontB}
-                <CharacterSlot
-                    {char}
-                    {proximity}
-                    {isPast}
-                />
+                <CharacterSlot {char} {proximity} {isPast} />
             {/if}
         {/each}
     </div>
@@ -176,59 +199,80 @@ $effect(() => {
 <!-- Hidden canvas used for text measurement by the helper -->
 <canvas bind:this={measureCanvas} class="hidden" width="1" height="1"></canvas>
 
-<div class="relative">
-    <div
-        bind:this={container}
-        role="slider"
-        tabindex="0"
-        aria-valuenow={Math.round(sliderPos)}
-        aria-label="Font comparison slider"
-        onpointerdown={startDragging}
-        class="
-            group relative w-full py-8 px-4 sm:py-12 sm:px-8 md:py-16 md:px-12 lg:py-20 lg:px-24 overflow-hidden
-            rounded-xl sm:rounded-2xl md:rounded-[2.5rem]
-            select-none touch-none cursor-ew-resize min-h-72 sm:min-h-96 flex flex-col justify-center
-            backdrop-blur-lg bg-linear-to-br from-gray-100/70 via-white/50 to-gray-100/60
-            border border-border-muted
-            shadow-[inset_0_4px_12px_0_rgba(0,0,0,0.12),inset_0_2px_4px_0_rgba(0,0,0,0.08),0_1px_2px_0_rgba(255,255,255,0.8)]
-            before:absolute before:inset-0 before:rounded-xl sm:before:rounded-2xl md:before:rounded-[2.5rem] before:p-px
-            before:bg-linear-to-br before:from-black/5 before:via-black/2 before:to-transparent
-            before:-z-10 before:blur-sm
-        "
-    >
-        <!-- Text Rendering Container -->
-        {#if isLoading}
-            <div out:fade={{ duration: 300 }}>
-                <Loader size={24} />
-            </div>
-        {:else}
+<!-- Main container with perspective and fixed height -->
+<div
+    class="
+        relative w-full flex justify-center items-center
+        perspective-distant perspective-origin-center transform-3d
+        rounded-xl sm:rounded-2xl md:rounded-[2.5rem]
+        min-h-72 sm:min-h-96
+        backdrop-blur-lg bg-linear-to-br from-gray-200/40 via-white/80 to-gray-100/60
+        border border-border-muted
+        shadow-[inset_2px_0_8px_rgba(0,0,0,0.05)]
+        before:absolute before:inset-0 before:rounded-xl sm:before:rounded-2xl md:before:rounded-[2.5rem] before:p-px
+        before:bg-linear-to-br before:from-black/5 before:via-black/2 before:to-transparent
+        before:-z-10 before:blur-sm
+        overflow-hidden
+        [perspective:1500px] perspective-origin-center transform-3d
+    "
+>
+    {#if isLoading}
+        <div out:fade={{ duration: 300 }}>
+            <Loader size={24} />
+        </div>
+    {:else}
+        <!-- Text Plan -->
+        <PerspectivePlan
+            manager={perspective}
+            class="absolute inset-0 flex justify-center origin-right w-full h-full"
+        >
             <div
+                bind:this={container}
+                role="slider"
+                tabindex="0"
+                aria-valuenow={Math.round(sliderPos)}
+                aria-label="Font comparison slider"
+                onpointerdown={startDragging}
                 class="
-                    relative flex flex-col items-center gap-3 sm:gap-4
-                    text-3xl sm:text-4xl md:text-5xl lg:text-6xl xl:text-7xl font-bold leading-[1.15]
-                    z-10 pointer-events-none text-center
-                    drop-shadow-[0_3px_6px_rgba(255,255,255,0.9)]
+                    relative w-full h-full flex justify-center
+                    py-8 px-4 sm:py-12 sm:px-8 md:py-16 md:px-12 lg:py-20 lg:px-24
+                    select-none touch-none cursor-ew-resize
                 "
-                style:perspective="1000px"
-                in:fade={{ duration: 300, delay: 300 }}
-                out:fade={{ duration: 300 }}
             >
-                {#each charComparison.lines as line, lineIndex}
-                    <div
-                        class="relative w-full whitespace-nowrap"
-                        style:height={`${typography.height}em`}
-                        style:display="flex"
-                        style:align-items="center"
-                        style:justify-content="center"
-                    >
-                        {@render renderLine(line, lineIndex)}
-                    </div>
-                {/each}
-            </div>
+                <div
+                    class="
+                        relative flex flex-col items-center gap-3 sm:gap-4
+                        text-3xl sm:text-4xl md:text-5xl lg:text-6xl xl:text-7xl font-bold leading-[1.15]
+                        z-10 pointer-events-none text-center
+                        drop-shadow-[0_3px_6px_rgba(255,255,255,0.9)]
+                        my-auto
+                    "
+                    in:fade={{ duration: 300, delay: 300 }}
+                    out:fade={{ duration: 300 }}
+                >
+                    {#each charComparison.lines as line, lineIndex}
+                        <div
+                            class="relative w-full whitespace-nowrap"
+                            style:height={`${typography.height}em`}
+                            style:display="flex"
+                            style:align-items="center"
+                            style:justify-content="center"
+                        >
+                            {@render renderLine(line, lineIndex)}
+                        </div>
+                    {/each}
+                </div>
 
-            <SliderLine {sliderPos} {isDragging} />
-        {/if}
-    </div>
-    <!-- Since there're slider controls inside we put them outside the main one -->
-    <Controls {sliderPos} {isDragging} {typographyControls} {container} />
+                <!-- Slider Line - visible in slider mode -->
+                {#if !isInSettingsMode}
+                    <SliderLine {sliderPos} {isDragging} />
+                {/if}
+            </div>
+        </PerspectivePlan>
+
+        <Controls
+            class="absolute inset-y-0 left-0 transition-all duration-150"
+            handleToggle={togglePerspective}
+        />
+    {/if}
 </div>