Code cleanup

2 files changed, 404 insertions, 252 deletions

diff --git a/src/ts/oneko.ts b/src/ts/oneko.ts
index 236c7cb..2cf3a9b 100644
--- a/src/ts/oneko.ts
+++ b/src/ts/oneko.ts
@@ -1,182 +1,179 @@
 // oneko.js: https://github.com/adryd325/oneko.js
 
-export function initOneko(): void {
-    const isReducedMotion =
-        window.matchMedia('(prefers-reduced-motion: reduce)') === true ||
-        window.matchMedia('(prefers-reduced-motion: reduce)').matches === true;
+type SpriteOffset = readonly [number, number];
 
-    if (isReducedMotion) return;
+type Direction = 'N' | 'NE' | 'E' | 'SE' | 'S' | 'SW' | 'W' | 'NW';
 
-    const nekoEl = document.createElement('div');
-    let persistPosition = true;
+type IdleAnimation =
+    | 'sleeping'
+    | 'scratchSelf'
+    | 'scratchWallN'
+    | 'scratchWallS'
+    | 'scratchWallE'
+    | 'scratchWallW';
 
-    let nekoPosX = 32;
-    let nekoPosY = 32;
+type SavedState = {
+    nekoPosX: number;
+    nekoPosY: number;
+    mousePosX: number;
+    mousePosY: number;
+    frameCount: number;
+    idleTime: number;
+    idleAnimation: IdleAnimation | null;
+    idleAnimationFrame: number;
+    bgPos: string;
+};
 
-    let mousePosX = 0;
-    let mousePosY = 0;
+const NEKO_STORAGE_KEY = 'oneko';
+const FRAME_INTERVAL_MS = 100;
 
-    let frameCount = 0;
-    let idleTime = 0;
-    let idleAnimation: string | null = null;
-    let idleAnimationFrame = 0;
+const NEKO_SIZE_PX = 32;
+const NEKO_HALF_SIZE_PX = NEKO_SIZE_PX / 2;
+const NEKO_SPEED_PX = 10;
 
-    const nekoSpeed = 10;
-    const spriteSets: Record<string, [number, number][]> = {
-        idle: [[-3, -3]],
-        alert: [[-7, -3]],
-        scratchSelf: [
-            [-5, 0],
-            [-6, 0],
-            [-7, 0],
-        ],
-        scratchWallN: [
-            [0, 0],
-            [0, -1],
-        ],
-        scratchWallS: [
-            [-7, -1],
-            [-6, -2],
-        ],
-        scratchWallE: [
-            [-2, -2],
-            [-2, -3],
-        ],
-        scratchWallW: [
-            [-4, 0],
-            [-4, -1],
-        ],
-        tired: [[-3, -2]],
-        sleeping: [
-            [-2, 0],
-            [-2, -1],
-        ],
-        N: [
-            [-1, -2],
-            [-1, -3],
-        ],
-        NE: [
-            [0, -2],
-            [0, -3],
-        ],
-        E: [
-            [-3, 0],
-            [-3, -1],
-        ],
-        SE: [
-            [-5, -1],
-            [-5, -2],
-        ],
-        S: [
-            [-6, -3],
-            [-7, -2],
-        ],
-        SW: [
-            [-5, -3],
-            [-6, -1],
-        ],
-        W: [
-            [-4, -2],
-            [-4, -3],
-        ],
-        NW: [
-            [-1, 0],
-            [-1, -1],
-        ],
-    };
+const IDLE_DISTANCE_THRESHOLD_PX = 48;
 
-    function init(): void {
-        const assetBase = window.ASSET_BASE || '';
-        let nekoFile = `${assetBase}/oneko/oneko.gif`;
-        const curScript = document.currentScript as HTMLScriptElement;
-        if (curScript?.dataset.cat) {
-            nekoFile = curScript.dataset.cat;
-        }
-        if (curScript?.dataset.persistPosition) {
-            if (curScript.dataset.persistPosition === '') {
-                persistPosition = true;
-            } else {
-                persistPosition = JSON.parse(curScript.dataset.persistPosition.toLowerCase());
-            }
-        }
+const spriteSets = {
+    idle: [[-3, -3]],
+    alert: [[-7, -3]],
+    scratchSelf: [
+        [-5, 0],
+        [-6, 0],
+        [-7, 0],
+    ],
+    scratchWallN: [
+        [0, 0],
+        [0, -1],
+    ],
+    scratchWallS: [
+        [-7, -1],
+        [-6, -2],
+    ],
+    scratchWallE: [
+        [-2, -2],
+        [-2, -3],
+    ],
+    scratchWallW: [
+        [-4, 0],
+        [-4, -1],
+    ],
+    tired: [[-3, -2]],
+    sleeping: [
+        [-2, 0],
+        [-2, -1],
+    ],
+    N: [
+        [-1, -2],
+        [-1, -3],
+    ],
+    NE: [
+        [0, -2],
+        [0, -3],
+    ],
+    E: [
+        [-3, 0],
+        [-3, -1],
+    ],
+    SE: [
+        [-5, -1],
+        [-5, -2],
+    ],
+    S: [
+        [-6, -3],
+        [-7, -2],
+    ],
+    SW: [
+        [-5, -3],
+        [-6, -1],
+    ],
+    W: [
+        [-4, -2],
+        [-4, -3],
+    ],
+    NW: [
+        [-1, 0],
+        [-1, -1],
+    ],
+} as const satisfies Record<string, readonly SpriteOffset[]>;
 
-        if (persistPosition) {
-            const storedNekoStr = window.localStorage.getItem('oneko');
-            const storedNeko = storedNekoStr ? JSON.parse(storedNekoStr) : null;
-            if (storedNeko !== null) {
-                nekoPosX = storedNeko.nekoPosX;
-                nekoPosY = storedNeko.nekoPosY;
-                mousePosX = storedNeko.mousePosX;
-                mousePosY = storedNeko.mousePosY;
-                frameCount = storedNeko.frameCount;
-                idleTime = storedNeko.idleTime;
-                idleAnimation = storedNeko.idleAnimation;
-                idleAnimationFrame = storedNeko.idleAnimationFrame;
-                nekoEl.style.backgroundPosition = storedNeko.bgPos;
-            }
-        }
+type SpriteName = keyof typeof spriteSets;
 
-        nekoEl.id = 'oneko';
-        nekoEl.ariaHidden = 'true';
-        nekoEl.style.width = '32px';
-        nekoEl.style.height = '32px';
-        nekoEl.style.position = 'fixed';
-        nekoEl.style.pointerEvents = 'none';
-        nekoEl.style.imageRendering = 'pixelated';
-        nekoEl.style.left = `${nekoPosX - 16}px`;
-        nekoEl.style.top = `${nekoPosY - 16}px`;
-        nekoEl.style.zIndex = '2147483647';
+function prefersReducedMotion(): boolean {
+    return window.matchMedia('(prefers-reduced-motion: reduce)').matches;
+}
 
-        nekoEl.style.backgroundImage = `url(${nekoFile})`;
+function clamp(value: number, min: number, max: number): number {
+    return Math.min(Math.max(min, value), max);
+}
 
-        document.body.appendChild(nekoEl);
+function safeJsonParse<T>(value: string | null): T | null {
+    if (!value) return null;
+    try {
+        return JSON.parse(value) as T;
+    } catch {
+        return null;
+    }
+}
 
-        document.addEventListener('mousemove', (event: MouseEvent) => {
-            mousePosX = event.clientX;
-            mousePosY = event.clientY;
-        });
+function parseBooleanAttribute(value: string): boolean | null {
+    const normalized = value.trim().toLowerCase();
+    if (normalized === 'true') return true;
+    if (normalized === 'false') return false;
+    return null;
+}
 
-        if (persistPosition) {
-            window.addEventListener('beforeunload', () => {
-                window.localStorage.setItem(
-                    'oneko',
-                    JSON.stringify({
-                        nekoPosX: nekoPosX,
-                        nekoPosY: nekoPosY,
-                        mousePosX: mousePosX,
-                        mousePosY: mousePosY,
-                        frameCount: frameCount,
-                        idleTime: idleTime,
-                        idleAnimation: idleAnimation,
-                        idleAnimationFrame: idleAnimationFrame,
-                        bgPos: nekoEl.style.backgroundPosition,
-                    })
-                );
-            });
-        }
+function sample<T>(items: readonly T[]): T {
+    return items[Math.floor(Math.random() * items.length)];
+}
 
-        window.requestAnimationFrame(onAnimationFrame);
+function directionFromVector(dx: number, dy: number): Direction {
+    // Screen coordinates: +x is right, +y is down.
+    // atan2 gives: 0 = E, π/2 = S, π = W, -π/2 = N.
+    const angle = Math.atan2(dy, dx);
+    const octant = (Math.round((8 * angle) / (2 * Math.PI)) + 8) % 8;
+
+    switch (octant) {
+        case 0:
+            return 'E';
+        case 1:
+            return 'SE';
+        case 2:
+            return 'S';
+        case 3:
+            return 'SW';
+        case 4:
+            return 'W';
+        case 5:
+            return 'NW';
+        case 6:
+            return 'N';
+        case 7:
+            return 'NE';
+        default:
+            return 'E';
     }
+}
 
-    let lastFrameTimestamp: number | undefined;
+export function initOneko(): void {
+    if (prefersReducedMotion()) return;
 
-    function onAnimationFrame(timestamp: number): void {
-        if (!nekoEl.isConnected) {
-            return;
-        }
-        if (!lastFrameTimestamp) {
-            lastFrameTimestamp = timestamp;
-        }
-        if (lastFrameTimestamp && timestamp - lastFrameTimestamp > 100) {
-            lastFrameTimestamp = timestamp;
-            frame();
-        }
-        window.requestAnimationFrame(onAnimationFrame);
-    }
+    const nekoEl = document.createElement('div');
+    let persistPosition = true;
+
+    let nekoPosX = NEKO_SIZE_PX;
+    let nekoPosY = NEKO_SIZE_PX;
 
-    function setSprite(name: string, frame: number): void {
+    let mousePosX = 0;
+    let mousePosY = 0;
+
+    let frameCount = 0;
+    let idleTime = 0;
+    let idleAnimation: IdleAnimation | null = null;
+    let idleAnimationFrame = 0;
+
+    function setSprite(name: SpriteName, frame: number): void {
         const sprite = spriteSets[name][frame % spriteSets[name].length];
-        nekoEl.style.backgroundPosition = `${sprite[0] * 32}px ${sprite[1] * 32}px`;
+        nekoEl.style.backgroundPosition = `${sprite[0] * NEKO_SIZE_PX}px ${sprite[1] * NEKO_SIZE_PX}px`;
     }
 
     function resetIdleAnimation(): void {
@@ -184,26 +181,83 @@ export function initOneko(): void {
         idleAnimationFrame = 0;
     }
 
+    function loadPersistedState(): void {
+        if (!persistPosition) return;
+
+        const stored = safeJsonParse<Partial<SavedState>>(
+            window.localStorage.getItem(NEKO_STORAGE_KEY)
+        );
+        if (!stored) return;
+
+        if (typeof stored.nekoPosX === 'number') nekoPosX = stored.nekoPosX;
+        if (typeof stored.nekoPosY === 'number') nekoPosY = stored.nekoPosY;
+        if (typeof stored.mousePosX === 'number') mousePosX = stored.mousePosX;
+        if (typeof stored.mousePosY === 'number') mousePosY = stored.mousePosY;
+        if (typeof stored.frameCount === 'number') frameCount = stored.frameCount;
+        if (typeof stored.idleTime === 'number') idleTime = stored.idleTime;
+        if (typeof stored.idleAnimationFrame === 'number')
+            idleAnimationFrame = stored.idleAnimationFrame;
+
+        if (stored.idleAnimation === null) {
+            idleAnimation = null;
+        } else if (typeof stored.idleAnimation === 'string') {
+            const allowed: IdleAnimation[] = [
+                'sleeping',
+                'scratchSelf',
+                'scratchWallN',
+                'scratchWallS',
+                'scratchWallE',
+                'scratchWallW',
+            ];
+            if (allowed.includes(stored.idleAnimation as IdleAnimation)) {
+                idleAnimation = stored.idleAnimation as IdleAnimation;
+            }
+        }
+
+        if (typeof stored.bgPos === 'string') {
+            nekoEl.style.backgroundPosition = stored.bgPos;
+        }
+    }
+
+    function saveState(): void {
+        if (!persistPosition) return;
+
+        const state: SavedState = {
+            nekoPosX,
+            nekoPosY,
+            mousePosX,
+            mousePosY,
+            frameCount,
+            idleTime,
+            idleAnimation,
+            idleAnimationFrame,
+            bgPos: nekoEl.style.backgroundPosition,
+        };
+
+        window.localStorage.setItem(NEKO_STORAGE_KEY, JSON.stringify(state));
+    }
+
     function idle(): void {
         idleTime += 1;
 
-        // every ~ 20 seconds
-        if (idleTime > 10 && Math.floor(Math.random() * 200) === 0 && idleAnimation == null) {
-            const avalibleIdleAnimations: string[] = ['sleeping', 'scratchSelf'];
-            if (nekoPosX < 32) {
-                avalibleIdleAnimations.push('scratchWallW');
+        // Every ~20 seconds, pick an idle animation.
+        if (idleTime > 10 && Math.floor(Math.random() * 200) === 0 && idleAnimation === null) {
+            const availableIdleAnimations: IdleAnimation[] = ['sleeping', 'scratchSelf'];
+
+            if (nekoPosX < NEKO_SIZE_PX) {
+                availableIdleAnimations.push('scratchWallW');
             }
-            if (nekoPosY < 32) {
-                avalibleIdleAnimations.push('scratchWallN');
+            if (nekoPosY < NEKO_SIZE_PX) {
+                availableIdleAnimations.push('scratchWallN');
             }
-            if (nekoPosX > window.innerWidth - 32) {
-                avalibleIdleAnimations.push('scratchWallE');
+            if (nekoPosX > window.innerWidth - NEKO_SIZE_PX) {
+                availableIdleAnimations.push('scratchWallE');
             }
-            if (nekoPosY > window.innerHeight - 32) {
-                avalibleIdleAnimations.push('scratchWallS');
+            if (nekoPosY > window.innerHeight - NEKO_SIZE_PX) {
+                availableIdleAnimations.push('scratchWallS');
             }
-            idleAnimation =
-                avalibleIdleAnimations[Math.floor(Math.random() * avalibleIdleAnimations.length)];
+
+            idleAnimation = sample(availableIdleAnimations);
         }
 
         switch (idleAnimation) {
@@ -212,6 +266,7 @@ export function initOneko(): void {
                     setSprite('tired', 0);
                     break;
                 }
+
                 setSprite('sleeping', Math.floor(idleAnimationFrame / 4));
                 if (idleAnimationFrame > 192) {
                     resetIdleAnimation();
@@ -231,46 +286,112 @@ export function initOneko(): void {
                 setSprite('idle', 0);
                 return;
         }
+
         idleAnimationFrame += 1;
     }
 
     function frame(): void {
         frameCount += 1;
+
         const diffX = nekoPosX - mousePosX;
         const diffY = nekoPosY - mousePosY;
         const distance = Math.sqrt(diffX ** 2 + diffY ** 2);
 
-        if (distance < nekoSpeed || distance < 48) {
+        if (distance < IDLE_DISTANCE_THRESHOLD_PX || distance < NEKO_SPEED_PX) {
             idle();
             return;
         }
 
-        idleAnimation = null;
-        idleAnimationFrame = 0;
+        resetIdleAnimation();
 
         if (idleTime > 1) {
             setSprite('alert', 0);
-            // count down after being alerted before moving
+            // Count down after being alerted before moving.
             idleTime = Math.min(idleTime, 7);
             idleTime -= 1;
             return;
         }
 
-        let direction = '';
-        direction += diffY / distance > 0.5 ? 'N' : '';
-        direction += diffY / distance < -0.5 ? 'S' : '';
-        direction += diffX / distance > 0.5 ? 'W' : '';
-        direction += diffX / distance < -0.5 ? 'E' : '';
+        const targetDx = mousePosX - nekoPosX;
+        const targetDy = mousePosY - nekoPosY;
+        const direction = directionFromVector(targetDx, targetDy);
         setSprite(direction, frameCount);
 
-        nekoPosX -= (diffX / distance) * nekoSpeed;
-        nekoPosY -= (diffY / distance) * nekoSpeed;
+        nekoPosX -= (diffX / distance) * NEKO_SPEED_PX;
+        nekoPosY -= (diffY / distance) * NEKO_SPEED_PX;
 
-        nekoPosX = Math.min(Math.max(16, nekoPosX), window.innerWidth - 16);
-        nekoPosY = Math.min(Math.max(16, nekoPosY), window.innerHeight - 16);
+        nekoPosX = clamp(nekoPosX, NEKO_HALF_SIZE_PX, window.innerWidth - NEKO_HALF_SIZE_PX);
+        nekoPosY = clamp(nekoPosY, NEKO_HALF_SIZE_PX, window.innerHeight - NEKO_HALF_SIZE_PX);
 
-        nekoEl.style.left = `${nekoPosX - 16}px`;
-        nekoEl.style.top = `${nekoPosY - 16}px`;
+        nekoEl.style.left = `${nekoPosX - NEKO_HALF_SIZE_PX}px`;
+        nekoEl.style.top = `${nekoPosY - NEKO_HALF_SIZE_PX}px`;
+    }
+
+    function init(): void {
+        const assetBase = window.ASSET_BASE ?? '';
+        let nekoFile = `${assetBase}/oneko/oneko.gif`;
+
+        const curScript = document.currentScript as HTMLScriptElement | null;
+        if (curScript?.dataset.cat) {
+            nekoFile = curScript.dataset.cat;
+        }
+
+        const persistPositionAttr = curScript?.dataset.persistPosition;
+        if (persistPositionAttr !== undefined) {
+            if (persistPositionAttr === '') {
+                persistPosition = true;
+            } else {
+                const parsed = parseBooleanAttribute(persistPositionAttr);
+                if (parsed !== null) {
+                    persistPosition = parsed;
+                }
+            }
+        }
+
+        nekoEl.id = 'oneko';
+        nekoEl.ariaHidden = 'true';
+        nekoEl.style.width = `${NEKO_SIZE_PX}px`;
+        nekoEl.style.height = `${NEKO_SIZE_PX}px`;
+        nekoEl.style.position = 'fixed';
+        nekoEl.style.pointerEvents = 'none';
+        nekoEl.style.imageRendering = 'pixelated';
+        nekoEl.style.zIndex = '2147483647';
+        nekoEl.style.backgroundImage = `url(${nekoFile})`;
+
+        loadPersistedState();
+
+        nekoEl.style.left = `${nekoPosX - NEKO_HALF_SIZE_PX}px`;
+        nekoEl.style.top = `${nekoPosY - NEKO_HALF_SIZE_PX}px`;
+
+        document.body.appendChild(nekoEl);
+
+        document.addEventListener('mousemove', (event: MouseEvent) => {
+            mousePosX = event.clientX;
+            mousePosY = event.clientY;
+        });
+
+        if (persistPosition) {
+            window.addEventListener('beforeunload', saveState);
+        }
+
+        window.requestAnimationFrame(onAnimationFrame);
+    }
+
+    let lastFrameTimestamp: number | undefined;
+
+    function onAnimationFrame(timestamp: number): void {
+        if (!nekoEl.isConnected) return;
+
+        if (lastFrameTimestamp === undefined) {
+            lastFrameTimestamp = timestamp;
+        }
+
+        if (timestamp - lastFrameTimestamp >= FRAME_INTERVAL_MS) {
+            lastFrameTimestamp = timestamp;
+            frame();
+        }
+
+        window.requestAnimationFrame(onAnimationFrame);
     }
 
     init();
diff --git a/src/ts/script.ts b/src/ts/script.ts
index 56c6d63..81c61f7 100644
--- a/src/ts/script.ts
+++ b/src/ts/script.ts
@@ -1,92 +1,123 @@
 import Prism from 'prismjs';
-import 'prismjs/components/prism-javascript';
 import 'prismjs/components/prism-css';
+import 'prismjs/components/prism-javascript';
 import 'prismjs/components/prism-markup';
 import { initOneko } from './oneko';
 
-// Auto-detect asset base from the bundled script's origin
-(() => {
-    window.ASSET_BASE = '';
-    const bundleScript = document.querySelector('script[src*="bundle"]');
-    if (bundleScript?.src) {
-        try {
-            const url = new URL(bundleScript.src, window.location.href);
-            window.ASSET_BASE = url.origin;
-        } catch {
-            // Fall back to empty string
-        }
-    }
-})();
+type Theme = 'light' | 'dark';
 
-(() => {
-    const toggleButton = document.getElementById('theme-toggle') as HTMLInputElement;
-    const html = document.documentElement;
+const THEME_STORAGE_KEY = 'theme';
+const DARK_THEME_ATTRIBUTE = 'data-theme';
 
-    const sessionTheme = sessionStorage.getItem('theme');
-    const systemPrefersDark = window.matchMedia('(prefers-color-scheme: dark)').matches;
+function detectAssetBase(): string {
+    const currentScript = document.currentScript as HTMLScriptElement | null;
+    const scriptSrc =
+        currentScript?.src ??
+        document.querySelector<HTMLScriptElement>('script[src*="bundle"]')?.src ??
+        '';
 
-    const initialTheme = sessionTheme || (systemPrefersDark ? 'dark' : 'light');
+    if (!scriptSrc) return '';
 
-    if (initialTheme === 'dark') {
-        html.setAttribute('data-theme', 'dark');
-        toggleButton.checked = true;
+    try {
+        return new URL(scriptSrc, window.location.href).origin;
+    } catch {
+        return '';
     }
+}
+
+function setAssetBase(): void {
+    window.ASSET_BASE = detectAssetBase();
+}
+
+function getSystemTheme(): Theme {
+    return window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
+}
+
+function applyTheme(theme: Theme): void {
+    if (theme === 'dark') {
+        document.documentElement.setAttribute(DARK_THEME_ATTRIBUTE, 'dark');
+    } else {
+        document.documentElement.removeAttribute(DARK_THEME_ATTRIBUTE);
+    }
+}
+
+function getStoredTheme(): Theme | null {
+    const theme = sessionStorage.getItem(THEME_STORAGE_KEY);
+    return theme === 'dark' || theme === 'light' ? theme : null;
+}
+
+function initThemeToggle(): void {
+    const toggleButton = document.getElementById('theme-toggle');
+    if (!(toggleButton instanceof HTMLInputElement)) return;
+
+    const initialTheme = getStoredTheme() ?? getSystemTheme();
+    applyTheme(initialTheme);
+    toggleButton.checked = initialTheme === 'dark';
 
     toggleButton.addEventListener('change', () => {
-        const theme = html.getAttribute('data-theme');
-
-        if (theme === 'dark') {
-            html.removeAttribute('data-theme');
-            sessionStorage.setItem('theme', 'light');
-            toggleButton.checked = false;
-        } else {
-            html.setAttribute('data-theme', 'dark');
-            sessionStorage.setItem('theme', 'dark');
-            toggleButton.checked = true;
-        }
+        const nextTheme: Theme = toggleButton.checked ? 'dark' : 'light';
+        applyTheme(nextTheme);
+        sessionStorage.setItem(THEME_STORAGE_KEY, nextTheme);
     });
-})();
+}
 
-(() => {
-    const colors = ['#ff69b4', '#b19cd9', '#8b6f47', '#ff85c0', '#c4b5fd', '#d4a574'];
-    const shapes = ['❀', '✿', '✽', '✾', '✻', '❊', '❋', '✼'];
+function sample<T>(items: readonly T[]): T {
+    return items[Math.floor(Math.random() * items.length)];
+}
 
-    document.addEventListener('mousemove', (e: MouseEvent) => {
-        createParticle(e.clientX, e.clientY);
-    });
+function initFairyDust(): void {
+    if (window.matchMedia('(prefers-reduced-motion: reduce)').matches) return;
 
-    const createParticle = (x: number, y: number) => {
+    const colors = ['#ff69b4', '#b19cd9', '#8b6f47', '#ff85c0', '#c4b5fd', '#d4a574'] as const;
+    const shapes = ['❀', '✿', '✽', '✾', '✻', '❊', '❋', '✼'] as const;
+
+    const particleLifetimeMs = 800;
+
+    function createParticle(x: number, y: number): void {
         const particle = document.createElement('div');
         particle.className = 'fairy-dust';
 
-        const shape = shapes[Math.floor(Math.random() * shapes.length)];
-        const size = Math.random() * 8 + 6;
-        const color = colors[Math.floor(Math.random() * colors.length)];
         const offsetX = (Math.random() - 0.5) * 20;
         const offsetY = (Math.random() - 0.5) * 20;
-        const rotation = Math.random() * 360;
-
-        particle.textContent = shape;
-        particle.style.cssText = `
-      position: fixed;
-      left: ${x + offsetX}px;
-      top: ${y + offsetY}px;
-      font-size: ${size}px;
-      color: ${color};
-      opacity: 0.4;
-      pointer-events: none;
-      z-index: 9001; /* it's over 9000 */
-      line-height: 1;
-      transform: rotate(${rotation}deg);
-      animation: fairy-float 0.8s ease-out forwards;
-    `;
+        const rotationDeg = Math.random() * 360;
+        const sizePx = Math.random() * 8 + 6;
+
+        particle.textContent = sample(shapes);
+        particle.style.left = `${x + offsetX}px`;
+        particle.style.top = `${y + offsetY}px`;
+        particle.style.fontSize = `${sizePx}px`;
+        particle.style.color = sample(colors);
+        particle.style.transform = `rotate(${rotationDeg}deg)`;
 
         document.body.appendChild(particle);
-        setTimeout(() => particle.remove(), 800);
-    };
-})();
+        window.setTimeout(() => particle.remove(), particleLifetimeMs);
+    }
+
+    // rAF throttle to avoid creating a particle per mouse event.
+    let latestX = 0;
+    let latestY = 0;
+    let scheduled = false;
 
-document.addEventListener('DOMContentLoaded', () => {
+    document.addEventListener('mousemove', (event: MouseEvent) => {
+        latestX = event.clientX;
+        latestY = event.clientY;
+
+        if (scheduled) return;
+        scheduled = true;
+
+        window.requestAnimationFrame(() => {
+            scheduled = false;
+            createParticle(latestX, latestY);
+        });
+    });
+}
+
+function init(): void {
+    setAssetBase();
+    initThemeToggle();
+    initFairyDust();
     Prism.highlightAll();
     initOneko();
-});
+}
+
+document.addEventListener('DOMContentLoaded', init);