:root {
    --bg: #F7F7F6;
    --surface: #FFFFFF;
    --panel: #EDEEEC;
    --ink: #1A2223;
    --ink-mid: #465557;
    --ink-soft: #6C7B7D;
    --line: #E0E2DF;
    --accent: #0C6F75;
    --accent-soft: #E1EFEF;
    --cta-ink: #FFFFFF;
    --heat: #C2551F;
    --f-body: 'Noto Sans TC', system-ui, -apple-system, sans-serif;
    --f-mono: 'IBM Plex Mono', ui-monospace, monospace;
  }
  @media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) {
      --bg: #0F1415; --surface: #161D1E; --panel: #1A2223; --ink: #E4E9E9; --ink-mid: #C2CFD0;
      --ink-soft: #9CABAC; --line: #2E3839; --accent: #3AB2B8; --accent-soft: #12302F;
      --cta-ink: #05191B; --heat: #EE8552;
    }
  }
  :root[data-theme="dark"] {
    --bg: #0F1415; --surface: #161D1E; --panel: #1A2223; --ink: #E4E9E9; --ink-mid: #C2CFD0;
    --ink-soft: #9CABAC; --line: #2E3839; --accent: #3AB2B8; --accent-soft: #12302F;
    --cta-ink: #05191B; --heat: #EE8552;
  }

  * { box-sizing: border-box; }
  body { margin: 0; background: var(--bg); color: var(--ink); font-family: var(--f-body); font-size: 16px; line-height: 1.85; -webkit-font-smoothing: antialiased; }
  .wrap { max-width: 52rem; margin: 0 auto; padding: 0 1.5rem; }
  a { color: var(--accent); }
  :is(a, button, input, select):focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; }

  .top { border-bottom: 1px solid var(--line); }
  .brandmark { display: flex; align-items: center; gap: 1rem; padding: 1.2rem 0; text-decoration: none; color: inherit; width: max-content; }
  .logochip { background: #241A18; border-radius: 6px; padding: .55rem .8rem; display: flex; }
  .logochip img { height: 44px; width: auto; display: block; }
  .brandmark .name { display: block; font-weight: 900; font-size: 1.25rem; letter-spacing: .03em; line-height: 1.3; }
  .brandmark .name b { font-weight: 700; font-size: .62em; color: var(--ink-mid); margin-left: .3rem; }
  .brandmark .cat { display: block; font-size: .95rem; color: var(--ink-mid); }

  .hero { padding: 3.2rem 0 1.6rem; }
  .eyebrow { font-size: .88rem; font-weight: 700; letter-spacing: .28em; color: var(--accent); margin: 0 0 .8rem; }
  h1 { font-weight: 900; font-size: clamp(1.9rem, 5vw, 2.7rem); line-height: 1.3; letter-spacing: -.015em; margin: 0 0 1rem; text-wrap: balance; }
  h2 { font-size: 1.45rem; line-height: 1.4; margin: 0 0 1rem; }
  .lede { font-size: 1.06rem; color: var(--ink-mid); max-width: 40rem; margin: 0; }

  /* ═══ 試算 ═══ */
  .calc { background: var(--surface); border: 2px solid var(--accent); border-radius: 14px; padding: 1.6rem; }
  .cin { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem 1.2rem; }
  .cin label { display: grid; gap: .35rem; font-size: .95rem; font-weight: 700; color: var(--ink-mid); }
  .cin input, .cin select { font: inherit; font-weight: 500; font-size: 1.05rem; color: var(--ink); background: var(--panel); border: 1px solid var(--line); border-radius: 8px; padding: .6rem .7rem; width: 100%; min-width: 0; }
  .cin .bill input { font-family: var(--f-mono); font-size: 1.3rem; font-weight: 600; }
  .cout { display: grid; grid-template-columns: repeat(3, 1fr); gap: .8rem; margin-top: 1.4rem; }
  .cout div { background: var(--accent); color: var(--cta-ink); border-radius: 10px; padding: .9rem 1rem; }
  .cout span { display: block; font-size: .9rem; font-weight: 700; opacity: .9; }
  .cout b { display: block; font-family: var(--f-mono); font-size: 1.9rem; font-weight: 600; line-height: 1.25; }
  .cout .big b { font-size: 2.3rem; }
  .ctag { display: inline-block; margin-top: .9rem; font-size: .8rem; font-weight: 700; letter-spacing: .12em; color: var(--ink-soft); border: 1.5px solid var(--line); border-radius: 4px; padding: .05rem .45rem; }
  .ceq { margin: .7rem 0 0; font-size: .92rem; color: var(--ink-mid); }
  .ceq b { font-family: var(--f-mono); color: var(--ink); }

  /* ═══ 怎麼算的 ═══ */
  .how { padding: 3.5rem 0 0; }
  .how > p { color: var(--ink-mid); margin: 0 0 1.4rem; }
  .formula { background: var(--panel); border-radius: 10px; padding: 1.3rem 1.5rem; margin-bottom: 1.8rem; }
  .formula .fk { margin: 0; font-size: .85rem; font-weight: 700; letter-spacing: .12em; color: var(--accent); }
  .formula .fx { margin: .3rem 0 .6rem; font-family: var(--f-mono); font-size: 1.75rem; font-weight: 600; line-height: 1.3; }
  .formula .fd { margin: 0; font-size: .96rem; color: var(--ink-mid); line-height: 1.8; }

  .bars { display: grid; gap: 1.1rem; }
  .bar-row { display: grid; grid-template-columns: 10rem 1fr 4.5rem; gap: 1.2rem; align-items: center; font-weight: 700; }
  .bar-row small { display: block; font-family: var(--f-mono); font-size: .8rem; color: var(--ink-soft); font-weight: 500; }
  .track { display: block; height: 20px; background: var(--line); border-radius: 3px; overflow: hidden; }
  .fill { display: block; height: 100%; border-radius: 3px; }
  .val { font-family: var(--f-mono); font-size: 1.6rem; font-weight: 600; text-align: right; }
  .cap { font-size: .92rem; color: var(--ink-soft); margin: .8rem 0 0; }
  .out { display: inline-flex; align-items: center; gap: 1rem; margin-top: 1.4rem; padding: 1rem 1.3rem; background: var(--accent); color: var(--cta-ink); border-radius: 6px; max-width: 100%; }
  .out .ov { font-family: var(--f-mono); font-size: 2.4rem; font-weight: 600; line-height: 1; }
  .out .ol { font-weight: 700; line-height: 1.45; }

  .steps { margin: 2rem 0 0; padding: 0; list-style: none; counter-reset: s; display: grid; gap: 1rem; }
  .steps li { background: var(--surface); border: 1px solid var(--line); border-radius: 10px; padding: 1rem 1.2rem 1rem 3.4rem; position: relative; }
  .steps li::before { counter-increment: s; content: counter(s); position: absolute; left: 1rem; top: 1rem; width: 1.7rem; height: 1.7rem; border-radius: 50%; background: var(--accent); color: var(--cta-ink); display: grid; place-items: center; font-family: var(--f-mono); font-weight: 600; font-size: .9rem; line-height: 1; }
  .steps b { display: block; font-size: 1.02rem; }
  .steps p { margin: .2rem 0 0; color: var(--ink-mid); font-size: .95rem; }
  .warn { margin: 1.6rem 0 0; font-size: .92rem; color: var(--ink-soft); line-height: 1.8; }

  .cta { display: inline-block; background: var(--accent); color: var(--cta-ink); font-weight: 700; padding: .75rem 1.5rem; border-radius: 4px; text-decoration: none; }
  .contact { border-top: 1px solid var(--line); margin-top: 3.5rem; padding: 3rem 0; display: grid; grid-template-columns: 1fr auto; gap: 2rem; align-items: center; }
  .contact h2 { margin: 0 0 .5rem; }
  .contact p { color: var(--ink-mid); margin: 0 0 1rem; }
  .phones { display: flex; flex-wrap: wrap; gap: .4rem 1.6rem; font-family: var(--f-mono); }
  .phones a { color: var(--ink); text-decoration: none; }
  .phones b { font-family: var(--f-body); font-size: .88rem; color: var(--ink-soft); margin-right: .45rem; }
  .line { display: flex; align-items: center; gap: .9rem; }
  .line img { width: 92px; height: 92px; background: #fff; padding: 5px; border-radius: 6px; display: block; }
  .line span { font-size: .92rem; color: var(--ink-mid); line-height: 1.6; }
  .links { display: flex; flex-wrap: wrap; gap: .5rem 1.6rem; margin-top: 1.2rem; font-weight: 700; }

  @media (max-width: 760px) {
    .calc { padding: 1.1rem; }
    .cin, .cout { grid-template-columns: 1fr; }
    .cout b, .cout .big b { font-size: 1.8rem; }
    .bar-row { grid-template-columns: 7rem 1fr 3.4rem; gap: .7rem; }
    .val { font-size: 1.3rem; }
    .formula .fx { font-size: 1.4rem; }
    .out .ov { font-size: 2rem; }
    .contact { grid-template-columns: 1fr; }
  }