77 lines
2.7 KiB
TypeScript
77 lines
2.7 KiB
TypeScript
 
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// Lightweight game audio: one looping "scene music" track plus synthesized one-shot
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// SFX. Zero dependencies. Browsers block autoplay until a user gesture, so music/SFX
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// are primed on the first pointer interaction.
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type Sfx = 'advance' | 'choice' | 'sting'
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const MUSIC_VOLUME = 0.5
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let ctx: AudioContext | null = null
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function audioContext() {
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if (!ctx) { const AC = window.AudioContext || (window as unknown as { webkitAudioContext?: typeof AudioContext }).webkitAudioContext; if (AC) ctx = new AC() }
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return ctx
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}
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const music = typeof Audio !== 'undefined' ? new Audio() : null
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if (music) music.loop = true
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let currentUrl: string | null = null
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let muted = false
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let pending = false
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let fadeTimer: number | undefined
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function fade(target: number, done?: () => void) {
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if (!music) return
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window.clearInterval(fadeTimer)
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const step = (target - music.volume) / 12 || (target > music.volume ? 0.1 : -0.1)
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fadeTimer = window.setInterval(() => {
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if (!music) return
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const next = music.volume + step
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if ((step >= 0 && next >= target) || (step <= 0 && next <= target)) { music.volume = target; window.clearInterval(fadeTimer); done?.() }
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else music.volume = Math.max(0, Math.min(1, next))
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}, 40)
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}
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function startMusic() {
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if (!music || !currentUrl || muted) return
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const promise = music.play()
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if (promise) promise.then(() => { pending = false; fade(MUSIC_VOLUME) }).catch(() => { pending = true })
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}
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export const audio = {
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// A null url inherits whatever is already playing; a new url crossfades to it.
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setMusic(url: string | null) {
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if (!music || url === currentUrl) return
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currentUrl = url
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if (!url) { fade(0, () => music.pause()); pending = false; return }
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music.src = url
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music.volume = 0
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startMusic()
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},
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toggleMute() {
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muted = !muted
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if (muted) fade(0)
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else if (currentUrl) startMusic()
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return muted
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},
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isMuted() { return muted },
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sfx(kind: Sfx) {
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if (muted) return
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const context = audioContext()
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if (!context || context.state !== 'running') return
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const osc = context.createOscillator(), gain = context.createGain()
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osc.type = 'sine'
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osc.frequency.value = kind === 'choice' ? 540 : kind === 'sting' ? 300 : 400
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const now = context.currentTime
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gain.gain.setValueAtTime(0.0001, now)
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gain.gain.exponentialRampToValueAtTime(0.07, now + 0.008)
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gain.gain.exponentialRampToValueAtTime(0.0001, now + 0.12)
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osc.connect(gain).connect(context.destination)
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osc.start(now); osc.stop(now + 0.13)
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},
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// Resume the context and retry pending music on a user gesture.
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resume() {
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void audioContext()?.resume?.()
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if (pending) startMusic()
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},
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}
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if (typeof window !== 'undefined') window.addEventListener('pointerdown', () => audio.resume())
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