kekec_bbs_v2/frontend/src/App.tsx

import cn from 'classnames'
import { useEffect, useRef, useState } from 'react'
import { BrowserRouter,
	 Link,
	 Navigate,
	 Route,
	 Routes,
	 useLocation } from 'react-router-dom'

import bgmSrc from '@/assets/music.mp3'
import ThreadListPage from '@/pages/threads/ThreadListPage'
import ThreadDetailPage from '@/pages/threads/ThreadDetailPage'

const colours = ['bg-fuchsia-500 dark:bg-fuchsia-900',
		 'bg-lime-500 dark:bg-lime-900',
		 'bg-cyan-500 dark:bg-cyan-900',
		 'bg-orange-500 dark:bg-orange-900',
		 'bg-pink-500 dark:bg-pink-900',
		 'bg-red-500 dark:bg-red-900',
		 'bg-blue-500 dark:bg-blue-900',
		 'bg-green-500 dark:bg-green-900',
		 'bg-yellow-500 dark:bg-yellow-900'] as const


const ScrollToTop = () => {
  const { pathname } = useLocation ()

  useEffect (() => {
    scrollTo (0, 0)
  }, [pathname])

  return null
}


export default () => {
  const bgmRef = useRef<HTMLAudioElement | null> (null)

  const [colourIndex, setColourIndex] = useState (0)
  const [mute, setMute] = useState (false)
  const [playing, setPlaying] = useState (false)

  useEffect (() => {
    bgmRef.current = new Audio (bgmSrc)
    bgmRef.current.loop = true
    bgmRef.current.volume = 1

    const playBGM = async () => {
      if (playing || !(bgmRef.current))
	return

      try
      {
	await bgmRef.current.play ()
	setPlaying (true)
      }
      catch
      {
	setPlaying (false)
      }
    }

    const bgmInterval = setInterval (playBGM, 1000)
    document.addEventListener ('click', playBGM)
    document.addEventListener ('touchstart', playBGM)

    const changeColour = () => {
      setColourIndex (Math.floor (Math.random () * colours.length))
    }
    changeColour ()
    const colouringInterval = setInterval (changeColour, 3000)

    return () => {
      clearInterval (bgmInterval)
      clearInterval (colouringInterval)
    }
  }, [])

  return (
      <BrowserRouter>
	<ScrollToTop />
	<div className={cn ('w-screen min-h-screen',
			    colours[colourIndex],
			    'transition-colors duration-[3s] ease-linear')}>
	  <div className="mx-auto max-w-[960px] px-4">
	    <header className="pt-6 mb-8">
	      <h1 className="text-center">
		<Link to="/"
		      className="text-7xl text-transparent whitespace-nowrap
				 bg-[linear-gradient(90deg,#ff0000,#ff8800,#ffff00,#00ff00,#00ffff,#0000ff,#ff00ff,#ff0000)]
				 bg-clip-text [transform:skewX(-13.5deg)]
				 inline-block bg-[length:200%_100%] animate-rainbow-scroll drop-shadow-[0_0_6px_black]
				 font-serif hover:text-transparent dark:hover:text-transparent">
		  クソ掲示板
		</Link>
	      </h1>
	      <div className="text-center my-6">
		{playing && (
		    <a href="#" onClick={ev => {
		      ev.preventDefault ()
		      bgmRef.current && setMute (bgmRef.current.muted = !(mute))
		    }}>
		      {mute ? 'やっぱり BGM が恋しい人用' : 'BGM がうるさい人用'}
		    </a>)}
	      </div>
	    </header>
	    <main className="mb-8">
	      <Routes>
		<Route path="/" element={<Navigate to="/threads" replace />} />
		<Route path="/threads" element={<ThreadListPage />} />
		<Route path="/threads/:id" element={<ThreadDetailPage />} />
	      </Routes>
	    </main>
	    <hr />
	    <footer className="text-center mt-8 pb-12 text-base text-gray-500 dark:text-gray-300">
	      © このペィジへの投稿は，すべて，パブリック・ドメインとします．
	    </footer>
	  </div>
	</div>
      </BrowserRouter>)
}