/* Background Audio Remover — Draft B "Studio"
   参考：refs/oxi-instruments（近黑底 + 灰白字、等宽小字、大号细体紧字距、1px 分隔线、白/亮色小按钮）、
         refs/audio-player-collectui（深色版播放器：波形即进度条、一个强调色）
   外部参考：simpleclean.app（大虚线上传框、两个大播放按钮）、cleanaudio.io（波形播放进度、同位置切换）
   颜色按 DESIGN.md §2.3：三级底色 + 1px 边框分层，不用投影；唯一强调色琥珀 #EFB939（深字）。圆角一套 4/8/12。 */
:root {
  --bg: #0B0F14;
  --surface: #141B22;
  --surface-2: #1C252F;
  --text: #EEF3FF;
  --text-2: rgba(200,225,255,.66);
  --text-3: rgba(200,225,255,.42);
  --line: rgba(255,255,255,.08);
  --line-2: rgba(255,255,255,.16);
  --accent: #EFB939;          /* text on it: #0B0F14, contrast 10.7:1 */
  --accent-ink: #0B0F14;
  --accent-soft: rgba(239,185,57,.12);
  --ok: #4ADE80;
  --wave-played: var(--accent);
  --wave-rest: #33404D;
  --wave-dim: #222C36;
  --wave-dim-played: #5C6672;
  --playhead: #FFFFFF;
  --r-sm: 4px; --r: 8px; --r-lg: 12px;
  --font: "Work Sans", system-ui, -apple-system, "Segoe UI", sans-serif;
  --mono: "Fragment Mono", ui-monospace, "SFMono-Regular", Menlo, monospace;
  color-scheme: dark;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; background: var(--bg); color: var(--text); font: 400 16px/1.65 var(--font); -webkit-font-smoothing: antialiased; }
a { color: var(--text); text-decoration: none; }
button { font: inherit; color: inherit; background: none; border: 0; padding: 0; cursor: pointer; text-align: inherit; }
h1, h2, h3, p { margin: 0; }
svg { display: block; }
.mono { font-family: var(--mono); font-size: 12px; line-height: 1.4; letter-spacing: .06em; text-transform: uppercase; color: var(--text-3); }
.label { font-family: var(--mono); font-size: 11px; letter-spacing: .08em; text-transform: uppercase; color: var(--text-3); margin-bottom: 12px; }
.label--gap { margin-top: 32px; }
.small { font-size: 14px; line-height: 1.55; color: var(--text-2); }

body[data-state=landing] [data-view]:not([data-view~=landing]),
body[data-state=processing] [data-view]:not([data-view~=processing]),
body[data-state=result] [data-view]:not([data-view~=result]),
body[data-state=paywall] [data-view]:not([data-view~=paywall]) { display: none !important; }
.stage, .hero { animation: rise .22s ease-out; }
@keyframes rise { from { opacity: 0; transform: translateY(6px); } }
@media (prefers-reduced-motion: reduce) { *, *::before, *::after { animation: none !important; transition: none !important; } html { scroll-behavior: auto; } }

/* draft toolbar */
.draftbar { display: flex; align-items: center; gap: 16px; padding: 8px 24px; background: #E8EDF5; color: #334155; font: 500 13px/1.3 var(--font); flex-wrap: wrap; }
.draftbar__tag { font-family: var(--mono); font-size: 11px; letter-spacing: .08em; text-transform: uppercase; color: #0B0F14; }
.draftbar__tabs { display: flex; gap: 4px; flex-wrap: wrap; }
.draftbar__tabs a { color: #334155; padding: 4px 10px; border-radius: 999px; }
.draftbar__tabs a[aria-current=true] { background: #0B0F14; color: #fff; }
.draftbar__note { margin-left: auto; color: #64748B; }
.draftbar__note a { color: #0B0F14; text-decoration: underline; }
.bare .draftbar { display: none; }

/* nav */
.nav { position: sticky; top: 0; z-index: 10; background: rgba(11,15,20,.86); backdrop-filter: blur(12px); border-bottom: 1px solid var(--line); }
.nav__in { max-width: 1760px; margin: 0 auto; height: 60px; padding: 0 24px; display: flex; align-items: center; gap: 32px; }
.logo { display: inline-flex; align-items: center; gap: 8px; font-weight: 500; font-size: 18px; letter-spacing: -.02em; }
.logo svg { width: 24px; height: 24px; }
.nav__links { display: flex; gap: 28px; margin: 0 auto; }
.nav__links a { font: 12px/1 var(--mono); letter-spacing: .06em; text-transform: uppercase; color: var(--text-2); }
.nav__links a:hover { color: var(--text); }

/* buttons */
.btn { display: inline-flex; align-items: center; justify-content: center; gap: 8px; height: 48px; padding: 0 24px; border-radius: var(--r); background: var(--accent); color: var(--accent-ink); font-weight: 600; font-size: 16px; transition: filter .15s, transform .15s; }
.btn:hover { filter: brightness(1.08); transform: translateY(-1px); }
.btn--sm { height: 36px; padding: 0 14px; font: 12px/1 var(--mono); letter-spacing: .06em; text-transform: uppercase; }
.btn--lg { height: 52px; padding: 0 28px; font-size: 17px; }
.btn--block { width: 100%; }
.btn--ghost { background: rgba(255,255,255,.08); color: var(--text); }
.btn--ghost:hover { background: rgba(255,255,255,.14); filter: none; }

/* layout 300 | 720 | 300 */
.shell { max-width: 1760px; margin: 0 auto; padding: 0 24px; display: grid; grid-template-columns: minmax(0, 720px); justify-content: center; gap: 64px; }
.side { display: none; }
@media (min-width: 1600px) {
  .shell { grid-template-columns: 280px minmax(0, 720px) 280px; }
  .side { display: block; }
  .side__sticky { position: sticky; top: 100px; padding-top: 80px; }
  .side--left .side__sticky { border-right: 1px solid var(--line); padding-right: 32px; min-height: 60vh; }
  .side--right .side__sticky { border-left: 1px solid var(--line); padding-left: 32px; min-height: 60vh; }
}
.main { min-width: 0; padding-bottom: 32px; }

/* hero */
.hero { padding: 72px 0 0; }
.eyebrow { color: var(--text-2); }
.eyebrow--ok { color: var(--ok); }
.hero h1 { font-size: 56px; line-height: 1.04; font-weight: 500; letter-spacing: -.045em; margin-top: 16px; }
.hero h1 span, .stage__title span, .sec h2 span { color: var(--text-3); }
.hero h1 span { display: block; margin-top: 8px; font-size: 30px; line-height: 1.2; letter-spacing: -.02em; }
.console { margin-top: 40px; background: var(--surface); border: 1px solid var(--line); border-radius: var(--r-lg); }
.drop { margin: 12px; border: 1.5px dashed rgba(239,185,57,.45); border-radius: var(--r); padding: 44px 24px 36px; display: grid; justify-items: center; gap: 16px; text-align: center; cursor: pointer; background: repeating-linear-gradient(135deg, rgba(255,255,255,.015) 0 8px, transparent 8px 16px); transition: border-color .15s, background-color .15s; outline: none; }
.drop:hover, .drop:focus-visible, .drop.is-over { border-color: var(--accent); background-color: var(--accent-soft); }
.drop__icon { width: 36px; height: 36px; color: var(--accent); }
.drop__title { font-size: 28px; font-weight: 500; letter-spacing: -.03em; }
.demo { border-top: 1px solid var(--line); padding: 16px 20px 20px; }
.demo__head { display: flex; justify-content: space-between; gap: 12px; }
.demo__wave { display: block; width: 100%; height: 48px; margin-top: 16px; cursor: pointer; }
.trust { list-style: none; padding: 0; margin: 20px 0 0; display: flex; gap: 24px; flex-wrap: wrap; color: var(--text-2); }
.trust li { display: flex; align-items: center; gap: 8px; }
.trust i { width: 6px; height: 6px; border-radius: 999px; background: var(--ok); }

/* two big play buttons (simpleclean) */
.twin { display: grid; grid-template-columns: 1fr 1fr; gap: 8px; margin-top: 12px; }
.big { height: 56px; border-radius: var(--r); border: 1px solid var(--line-2); display: flex; align-items: center; justify-content: center; gap: 10px; font-size: 17px; font-weight: 500; transition: background .15s, border-color .15s, color .15s; }
.big svg { width: 20px; height: 20px; }
.big:hover { border-color: var(--text-2); }
body[data-mode=orig] .big[data-mode=orig], body[data-mode=clean] .big--clean { border-color: var(--text); }
.big--clean { color: var(--accent); }
body[data-mode=clean] .big--clean { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }
.big .i-pause { display: none; }
.big.is-live .i-play { display: none; }
.big.is-live .i-pause { display: block; }
/* landing demo: only the Choose file button is filled; a play button fills while it plays */
body[data-mode] .demo .big { background: none; color: var(--text); border-color: var(--line-2); }
body[data-mode] .demo .big--clean { color: var(--accent); border-color: rgba(239,185,57,.5); }
body[data-mode] .demo .big.is-live { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }

/* stages */
.stage { padding: 64px 0 0; }
.stage__title { font-size: 48px; line-height: 1.05; font-weight: 500; letter-spacing: -.04em; margin-top: 12px; }
.hint { font-size: 14px; color: var(--text-3); margin-top: 16px; }

/* processing */
.procbig { display: flex; align-items: flex-end; gap: 24px; margin-top: 20px; flex-wrap: wrap; }
.procbig__pct { font: 400 128px/.85 var(--font); letter-spacing: -.07em; font-variant-numeric: tabular-nums; }
.procbig__side { display: grid; gap: 6px; padding-bottom: 6px; min-width: 0; }
.procbig__side b { font-size: 22px; font-weight: 500; letter-spacing: -.01em; }
.lanes { margin-top: 32px; border: 1px solid var(--line); border-radius: var(--r-lg); background: var(--surface); overflow: hidden; }
.lane { position: relative; display: block; width: 100%; padding: 28px 16px 12px; border-top: 1px solid var(--line); }
.lane:first-child, .ruler + .lane { border-top: 0; }
.ruler + .lane { border-top: 1px solid var(--line); }
.lane__tag { position: absolute; left: 16px; top: 10px; font-size: 10px; }
.lane canvas { display: block; width: 100%; height: 64px; cursor: pointer; }
.lanes--proc { --p: .5; }
.lanes--proc .lane:first-child canvas { --wave-played: #4A5866; --wave-rest: #4A5866; cursor: default; }
.lanes--proc .lane--fill canvas { --wave-played: var(--accent); --wave-rest: var(--accent); cursor: default;
  clip-path: inset(0 calc((1 - var(--p)) * 100%) 0 0); }
.scan { position: absolute; top: 8px; bottom: 8px; width: 2px; background: var(--playhead); left: calc(16px + (100% - 32px) * var(--p)); box-shadow: 0 0 12px rgba(255,255,255,.5); }
.steps { list-style: none; padding: 0; margin: 24px 0 0; display: grid; grid-template-columns: repeat(3, 1fr); gap: 8px; }
.steps li { padding: 12px; border: 1px solid var(--line); border-radius: var(--r); color: var(--text-3); }
.steps li[data-status=now] { color: var(--accent); border-color: rgba(239,185,57,.5); }
.steps li[data-status=done] { color: var(--ok); }
.steps li[data-status=done]::after { content: " ✓"; }
.row-end { display: flex; justify-content: flex-end; margin-top: 16px; }
.titlerow { display: flex; align-items: flex-end; justify-content: space-between; gap: 16px; }
.quickdl { flex: none; margin-bottom: 2px; }
.mobilebar { display: none; }

/* result */
.video { position: relative; margin-top: 24px; border-radius: var(--r-lg); overflow: hidden; border: 1px solid var(--line); aspect-ratio: 16 / 9; max-height: 340px; width: 100%; background: #000; }
.video video { width: 100%; height: 100%; object-fit: contain; display: block; }
.video__badge { position: absolute; left: 12px; top: 12px; padding: 6px 10px; border-radius: var(--r-sm); background: rgba(11,15,20,.8); color: var(--text); }
body[data-mode=orig] .b-clean, body[data-mode=clean] .b-orig { display: none; }
body[data-mode=clean] .video__badge { color: var(--accent); }
.twin--result { margin-top: 12px; }
.ruler { display: flex; justify-content: space-between; padding: 8px 16px; font-size: 10px; border-bottom: 1px solid var(--line); background: var(--surface-2); }
.lanes .lane[data-qc=mode][aria-pressed=true] { background: var(--surface-2); }
.lanes .lane[data-qc=mode][aria-pressed=true] .lane__tag { color: var(--text); }
.lanes .lane[data-qc=mode][aria-pressed=true]::before { content: ""; position: absolute; left: 0; top: 0; bottom: 0; width: 3px; background: var(--accent); }
.lanes__hint { margin-top: 12px; font-size: 11px; }
.panel { margin-top: 24px; border: 1px solid var(--line); border-radius: var(--r-lg); background: var(--surface); display: grid; grid-template-columns: 1fr 1fr; }
.warmth { padding: 24px; border-right: 1px solid var(--line); }
.warmth__head { display: flex; justify-content: space-between; align-items: baseline; }
.warmth label { font-size: 18px; font-weight: 500; letter-spacing: -.01em; }
.warmth output { color: var(--accent); }
.range { --v: 0%; width: 100%; margin: 20px 0 4px; height: 28px; background: transparent; -webkit-appearance: none; appearance: none; cursor: pointer; }
.range::-webkit-slider-runnable-track { height: 4px; border-radius: 999px; background: linear-gradient(90deg, var(--accent) var(--v), var(--wave-rest) var(--v)); }
.range::-moz-range-track { height: 4px; border-radius: 999px; background: linear-gradient(90deg, var(--accent) var(--v), var(--wave-rest) var(--v)); }
.range::-webkit-slider-thumb { -webkit-appearance: none; width: 14px; height: 28px; margin-top: -12px; border-radius: var(--r-sm); background: var(--text); }
.range::-moz-range-thumb { width: 14px; height: 28px; border: 0; border-radius: var(--r-sm); background: var(--text); }
.range__ticks { height: 8px; margin: 0 6px 12px; background: repeating-linear-gradient(90deg, var(--line-2) 0 1px, transparent 1px 10%); }
.dl { padding: 24px; display: grid; align-content: center; gap: 12px; }
.dl__meta { font-size: 11px; text-align: center; }
.dl__more { display: flex; justify-content: center; gap: 20px; font-size: 14px; }
.dl__more a { color: var(--text-2); text-decoration: underline; text-underline-offset: 3px; }

/* paywall */
.previewrow { margin-top: 24px; padding: 16px; border: 1px solid var(--line); border-radius: var(--r-lg); background: var(--surface); }
.twin--tight { margin-top: 0; }
.twin--tight .big { height: 48px; font-size: 16px; }
.previewrow__wave { display: block; width: 100%; height: 44px; margin: 16px 0 8px; cursor: pointer; }
.previewrow .mono { font-size: 11px; }
.plans { margin-top: 16px; display: grid; grid-template-columns: 1fr 1fr; border: 1px solid var(--line); border-radius: var(--r-lg); overflow: hidden; }
.plan { padding: 28px 24px 24px; display: grid; gap: 12px; align-content: start; cursor: pointer; outline: none; position: relative; transition: background .15s; }
.plan + .plan { border-left: 1px solid var(--line); }
.plan.is-picked { background: var(--surface-2); }
.plan.is-picked::before { content: ""; position: absolute; left: 0; right: 0; top: 0; height: 3px; background: var(--accent); }
.plan:not(.is-picked) .btn { background: rgba(255,255,255,.08); color: var(--text); }
.plan__price { font-size: 64px; line-height: .95; font-weight: 400; letter-spacing: -.05em; }
.plan__price span { font-size: 20px; letter-spacing: -.01em; color: var(--text-3); }
.plan__per { font-size: 11px; }
.ticklist { list-style: none; padding: 0; margin: 4px 0 8px; display: grid; gap: 6px; font-size: 15px; color: var(--text-2); }
.ticklist li::before { content: "+ "; color: var(--accent); font-family: var(--mono); }
.foot { margin-top: 16px; font-size: 11px; text-align: center; }

/* below the fold */
.sec { padding: 112px 0 0; }
.sec h2 { font-size: 44px; line-height: 1.06; font-weight: 500; letter-spacing: -.04em; margin-top: 12px; }
.grid3 { list-style: none; padding: 0; margin: 40px 0 0; display: grid; grid-template-columns: repeat(3, 1fr); border-top: 1px solid var(--line); }
.grid3 li { padding: 20px 20px 0 0; display: grid; gap: 8px; align-content: start; }
.grid3 li + li { padding-left: 20px; border-left: 1px solid var(--line); }
.grid3 .mono { color: var(--accent); }
.grid3 h3 { font-size: 20px; font-weight: 500; letter-spacing: -.01em; line-height: 1.3; }
.grid3 p { font-size: 15px; color: var(--text-2); line-height: 1.55; }
.uses { margin-top: 40px; display: grid; grid-template-columns: 1fr 1fr; border: 1px solid var(--line); border-radius: var(--r-lg); overflow: hidden; }
.use { position: relative; display: grid; gap: 6px; padding: 24px; border-bottom: 1px solid var(--line); transition: background .15s; }
.use:nth-child(odd) { border-right: 1px solid var(--line); }
.use:nth-last-child(-n+2) { border-bottom: 0; }
.use:hover { background: var(--surface); }
.use b { font-size: 19px; font-weight: 500; letter-spacing: -.01em; line-height: 1.3; }
.use > span:not(.mono) { font-size: 14px; color: var(--text-2); line-height: 1.5; }
.use .mono { color: var(--accent); font-size: 11px; }
.use i { position: absolute; right: 20px; top: 20px; font-style: normal; color: var(--text-3); }
.note { margin-top: 16px; font-size: 14px; color: var(--text-3); }
.pricegrid { margin-top: 40px; display: grid; grid-template-columns: repeat(3, 1fr); border-top: 1px solid var(--line); }
.pricegrid > div { padding: 20px 20px 0 0; display: grid; gap: 8px; align-content: start; }
.pricegrid > div + div { padding-left: 20px; border-left: 1px solid var(--line); }
.pricegrid b { font-size: 48px; font-weight: 400; letter-spacing: -.05em; line-height: 1; }
.pricegrid small { font-size: 16px; color: var(--text-3); letter-spacing: 0; }
.pricegrid p { font-size: 15px; color: var(--text-2); line-height: 1.5; }
.alt { display: grid; gap: 8px; padding: 32px; border: 1px solid var(--line); border-radius: var(--r-lg); background: var(--surface); position: relative; }
.alt b { font-size: 28px; font-weight: 500; letter-spacing: -.03em; line-height: 1.15; max-width: 520px; }
.alt > span:not(.mono) { color: var(--text-2); }
.alt i { font-style: normal; justify-self: start; margin-top: 8px; padding: 8px 14px; border-radius: var(--r-sm); background: var(--text); color: var(--bg); font: 12px/1 var(--mono); text-transform: uppercase; letter-spacing: .06em; }
.faq { margin-top: 32px; border-top: 1px solid var(--line); }
.faq details { border-bottom: 1px solid var(--line); }
.faq summary { list-style: none; cursor: pointer; padding: 20px 40px 20px 0; font-size: 19px; font-weight: 500; letter-spacing: -.01em; position: relative; }
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after { content: "+"; position: absolute; right: 4px; top: 16px; font: 22px/1.4 var(--mono); color: var(--text-3); }
.faq details[open] summary::after { content: "–"; color: var(--accent); }
.faq details p { padding: 0 0 20px; color: var(--text-2); max-width: 640px; }

/* side panels */
.toc { list-style: none; padding: 0; margin: 0; display: grid; gap: 4px; counter-reset: t; }
.toc a { display: flex; gap: 12px; padding: 6px 0; color: var(--text-2); font-size: 15px; }
.toc a::before { counter-increment: t; content: "0" counter(t); font: 12px/1.9 var(--mono); color: var(--text-3); }
.toc a:hover { color: var(--accent); }
.log { list-style: none; padding: 0; margin: 0; display: grid; gap: 10px; font: 12px/1.5 var(--mono); color: var(--text-2); }
.log li { display: flex; gap: 12px; }
.log time { color: var(--text-3); flex: none; width: 40px; }
.log .is-now { color: var(--accent); }
.big-zero { font-size: 56px; line-height: 1; font-weight: 400; letter-spacing: -.05em; }
.specs { margin: 0; border-top: 1px solid var(--line); }
.specs div { display: flex; justify-content: space-between; padding: 10px 0; border-bottom: 1px solid var(--line); font-size: 14px; }
.specs dt { color: var(--text-3); font: 12px/1.7 var(--mono); text-transform: uppercase; letter-spacing: .06em; }
.specs dd { margin: 0; }
.drop--side { margin: 24px 0 0; padding: 20px; }

/* footer */
.foot-site { margin-top: 128px; border-top: 1px solid var(--line); }
.foot-site__in { max-width: 1168px; margin: 0 auto; padding: 56px 24px 32px; display: grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap: 32px; }
.foot-site__in > div { display: grid; gap: 8px; align-content: start; }
.foot-site__in a:not(.logo) { color: var(--text-2); font-size: 15px; }
.foot-site__base { max-width: 1168px; margin: 0 auto; padding: 16px 24px 32px; border-top: 1px solid var(--line); }

@media (max-width: 900px) {
  .nav__links { display: none; }
  .nav .btn { margin-left: auto; }
  .foot-site__in { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 640px) {
  .draftbar { padding: 6px 16px; gap: 8px; font-size: 12px; }
  .draftbar { flex-wrap: nowrap; overflow-x: auto; }
  .draftbar__tabs { flex-wrap: nowrap; white-space: nowrap; }
  .draftbar__note { display: none; }
  .nav__in { height: 56px; padding: 0 16px; gap: 12px; }
  .logo { font-size: 15px; gap: 6px; }
  .nav .btn--sm { padding: 0 10px; }
  .shell { padding: 0 16px; }
  .hero { padding-top: 28px; }
  .eyebrow { font-size: 11px; }
  .hero h1 { font-size: 34px; letter-spacing: -.04em; margin-top: 10px; }
  .hero h1 span { font-size: 20px; margin-top: 6px; }
  .console { margin-top: 20px; }
  .drop { margin: 8px; padding: 28px 16px 24px; gap: 12px; }
  .drop__title { font-size: 22px; }
  .drop .btn--lg { width: 100%; }
  .demo { padding: 12px; }
  .demo__head .mono:last-child { display: none; }
  .big { height: 52px; font-size: 16px; }
  .trust { gap: 8px 16px; font-size: 11px; }
  .stage { padding-top: 28px; }
  .stage__title { font-size: 34px; }
  .procbig__pct { font-size: 96px; }
  .steps { grid-template-columns: 1fr; }
  .lane { padding: 24px 12px 8px; }
  .lane canvas { height: 48px; }
  .ruler { padding: 6px 12px; }
  .panel { grid-template-columns: 1fr; }
  .warmth { border-right: 0; border-bottom: 1px solid var(--line); padding: 20px 16px; }
  .dl { padding: 20px 16px; }
  .plans { grid-template-columns: 1fr; }
  .plan + .plan { border-left: 0; border-top: 1px solid var(--line); }
  .plan__price { font-size: 52px; }
  .sec { padding-top: 72px; }
  .sec h2 { font-size: 32px; }
  .grid3, .pricegrid { grid-template-columns: 1fr; }
  .grid3 li, .grid3 li + li, .pricegrid > div, .pricegrid > div + div { padding: 20px 0; border-left: 0; border-bottom: 1px solid var(--line); }
  .uses { grid-template-columns: 1fr; }
  .use:nth-child(odd) { border-right: 0; }
  .use:nth-last-child(2) { border-bottom: 1px solid var(--line); }
  .alt { padding: 24px; }
  .alt b { font-size: 24px; }
  .foot-site { margin-top: 72px; }
  .quickdl { display: none; }
  body[data-state=result] { padding-bottom: 76px; }
  body[data-state=result] .mobilebar { display: block; position: fixed; left: 0; right: 0; bottom: 0; z-index: 20; padding: 12px 16px calc(12px + env(safe-area-inset-bottom)); background: rgba(11,15,20,.9); backdrop-filter: blur(12px); border-top: 1px solid var(--line); }
}