/* ============================================================
   Power Board — marketing site
   System-font, auto dark/light, no framework, no build step.
   ============================================================ */

:root {
  --accent: #0071e3;
  --accent-strong: #0058b9;
  --bg: #fbfbfd;
  --bg-elev: #ffffff;
  --fg: #1d1d1f;
  --fg-soft: #515154;
  --muted: #86868b;
  --line: #e3e3e8;
  --line-strong: #d2d2d7;
  --code-bg: #f5f5f7;
  --shadow: 0 1px 2px rgba(0,0,0,.04), 0 8px 24px rgba(0,0,0,.06);
  --radius: 14px;
  --radius-sm: 10px;
  --maxw: 980px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --accent: #0a84ff;
    --accent-strong: #3395ff;
    --bg: #000000;
    --bg-elev: #1c1c1e;
    --fg: #f5f5f7;
    --fg-soft: #c7c7cc;
    --muted: #8e8e93;
    --line: #2c2c2e;
    --line-strong: #3a3a3c;
    --code-bg: #0d0d0f;
    --shadow: 0 1px 2px rgba(0,0,0,.4), 0 12px 32px rgba(0,0,0,.5);
  }
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: -apple-system, BlinkMacSystemFont, "SF Pro Text", "SF Pro Display",
               "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei",
               system-ui, sans-serif;
  font-size: 17px;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
code {
  font-family: ui-monospace, "SF Mono", "JetBrains Mono", Menlo, Consolas, monospace;
  font-size: .88em;
  background: var(--code-bg);
  padding: 1px 6px;
  border-radius: 6px;
}

/* ───────────────────────── NAV ───────────────────────── */
.nav {
  position: sticky; top: 0; z-index: 50;
  display: flex; align-items: center; justify-content: space-between;
  padding: 12px max(20px, calc((100vw - var(--maxw)) / 2));
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  background: color-mix(in srgb, var(--bg) 78%, transparent);
  border-bottom: 1px solid var(--line);
}
.brand { display: flex; align-items: center; gap: 9px; color: var(--fg); font-weight: 600; font-size: 17px; }
.brand:hover { text-decoration: none; }
.brand-icon { border-radius: 7px; }
.nav-links { display: flex; align-items: center; gap: 22px; }
.nav-links a { color: var(--fg-soft); font-size: 15px; }
.nav-links a:hover { color: var(--fg); text-decoration: none; }
.lang-toggle {
  font: inherit; font-size: 14px; color: var(--accent);
  background: transparent; border: 1px solid var(--accent); border-radius: 999px;
  padding: 4px 12px; cursor: pointer; line-height: 1.4;
}
.lang-toggle:hover { background: color-mix(in srgb, var(--accent) 10%, transparent); }

/* ───────────────────────── HERO ───────────────────────── */
.hero {
  text-align: center;
  padding: clamp(56px, 10vw, 110px) 20px 64px;
  max-width: var(--maxw);
  margin: 0 auto;
}
.hero-icon {
  width: 128px; height: 128px;
  border-radius: 28px;
  box-shadow: 0 8px 30px rgba(0,0,0,.18);
  margin-bottom: 22px;
}
.hero-title {
  font-size: clamp(40px, 7vw, 64px);
  letter-spacing: -.02em;
  margin: 0 0 14px;
  font-weight: 700;
}
.hero-tag {
  font-size: clamp(18px, 2.4vw, 22px);
  color: var(--fg-soft);
  max-width: 640px;
  margin: 0 auto 26px;
  line-height: 1.45;
}
kbd {
  font-family: inherit; font-size: .9em;
  background: var(--bg-elev); border: 1px solid var(--line-strong);
  border-bottom-width: 2px; border-radius: 6px;
  padding: 1px 6px; color: var(--fg);
}
.meta-chips { display: flex; flex-wrap: wrap; gap: 8px; justify-content: center; margin-bottom: 30px; }
.chip {
  font-size: 13px; color: var(--fg-soft);
  background: var(--bg-elev); border: 1px solid var(--line);
  padding: 5px 12px; border-radius: 999px;
}
.cta-row { display: flex; flex-direction: column; align-items: center; gap: 10px; }
.btn {
  display: inline-flex; align-items: center; gap: 9px;
  font-size: 17px; font-weight: 500;
  padding: 13px 30px; border-radius: 999px;
  border: 1px solid transparent; cursor: pointer;
  transition: transform .05s ease, background .15s ease;
}
.btn:active { transform: scale(.98); }
.btn-primary { background: var(--accent); color: #fff; }
.btn-primary:hover { background: var(--accent-strong); text-decoration: none; }
.btn-icon { width: 19px; height: 19px; }
.cta-note { color: var(--muted); font-size: 13px; }

/* ───────────────────────── SECTIONS ───────────────────────── */
.section { max-width: var(--maxw); margin: 0 auto; padding: 56px 20px; border-top: 1px solid var(--line); }
.section-title { font-size: clamp(28px, 4vw, 36px); letter-spacing: -.01em; margin: 0 0 10px; font-weight: 700; }
.section-lede { color: var(--fg-soft); max-width: 640px; margin: 0 0 8px; font-size: 18px; }

/* feature cards */
.card-grid {
  display: grid; gap: 14px; margin-top: 28px;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
}
.card {
  background: var(--bg-elev); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 22px;
}
.card-icon {
  width: 38px; height: 38px; border-radius: 10px;
  display: grid; place-items: center; margin-bottom: 14px;
  color: #fff; background: linear-gradient(135deg, var(--accent), var(--accent-strong));
}
.card-icon svg { width: 21px; height: 21px; }
.card h3 { margin: 0 0 6px; font-size: 18px; }
.card p { margin: 0; color: var(--fg-soft); font-size: 15px; }

/* ───────────────────────── STEPS ───────────────────────── */
.steps { list-style: none; padding: 0; margin: 30px 0 0; counter-reset: step; }
.step {
  display: grid; grid-template-columns: 44px 1fr; gap: 18px;
  padding: 24px 0; border-bottom: 1px solid var(--line);
}
.step:last-child { border-bottom: none; }
.step-num {
  width: 34px; height: 34px; border-radius: 50%;
  background: var(--accent); color: #fff;
  display: grid; place-items: center; font-weight: 600; font-size: 16px;
}
.step-body h3 { margin: 4px 0 8px; font-size: 20px; }
.step-body p { margin: 0 0 12px; color: var(--fg-soft); }

.two-col { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin-top: 14px; }
@media (max-width: 720px) { .two-col { grid-template-columns: 1fr; } }
.subcard {
  background: var(--bg-elev); border: 1px solid var(--line);
  border-radius: var(--radius-sm); padding: 16px;
}
.subcard h4 { margin: 0 0 8px; font-size: 15px; }
.tight { margin: 0 0 10px; padding-left: 18px; }
.tight li { margin: 4px 0; font-size: 14px; color: var(--fg-soft); }
.step-note { margin: 12px 0 0; font-size: 14px; color: var(--accent); }

/* copyable code */
.codeblock {
  position: relative; background: var(--code-bg); border: 1px solid var(--line);
  border-radius: 8px; padding: 12px 76px 12px 12px; margin-top: 8px;
}
.codeblock code {
  background: transparent; padding: 0; font-size: 13px;
  word-break: break-all; white-space: pre-wrap; color: var(--fg);
}
.copy-btn {
  position: absolute; top: 8px; right: 8px;
  font-size: 12px; color: var(--accent); background: var(--bg-elev);
  border: 1px solid var(--line-strong); border-radius: 6px; padding: 4px 10px; cursor: pointer;
}
.copy-btn:hover { background: color-mix(in srgb, var(--accent) 10%, transparent); }
.copy-btn.copied { color: #1bbf5a; border-color: #1bbf5a; }

/* ───── faux macOS UI (the "示意图") ───── */
.mock-dialog {
  margin-top: 14px; background: var(--bg-elev);
  border: 1px solid var(--line-strong); border-radius: 11px;
  box-shadow: var(--shadow); overflow: hidden;
}
.mock-dialog-bar {
  display: flex; gap: 6px; padding: 9px 12px;
  background: color-mix(in srgb, var(--fg) 5%, var(--bg-elev));
  border-bottom: 1px solid var(--line);
}
.dot { width: 11px; height: 11px; border-radius: 50%; display: inline-block; }
.dot.r { background: #ff5f57; } .dot.y { background: #febc2e; } .dot.g { background: #28c840; }
.mock-dialog-body { display: flex; gap: 14px; padding: 18px; align-items: center; }
.mock-icon { border-radius: 9px; flex: none; }
.mock-line { margin: 0; font-size: 15px; font-weight: 600; }
.mock-sub { margin: 3px 0 0; font-size: 13px; color: var(--muted); }
.mock-dialog-actions { display: flex; justify-content: flex-end; gap: 8px; padding: 0 16px 16px; }
.mock-btn {
  font: inherit; font-size: 13px; padding: 6px 14px; cursor: default;
  border-radius: 7px; border: 1px solid var(--line-strong);
  background: var(--bg-elev); color: var(--fg);
}
.mock-btn.primary { background: var(--accent); color: #fff; border-color: var(--accent); }
.mock-caption { margin: 10px 0 0; font-size: 13px; color: var(--muted); font-style: italic; }

/* faux System Settings panel */
.mock-settings {
  background: var(--bg-elev); border: 1px solid var(--line-strong);
  border-radius: var(--radius-sm); overflow: hidden; box-shadow: var(--shadow);
}
.mock-settings-head { padding: 16px 16px 0; font-weight: 700; font-size: 16px; }
.mock-settings-sub { padding: 2px 16px 12px; font-size: 12px; color: var(--muted); border-bottom: 1px solid var(--line); }
.mock-list { list-style: none; margin: 0; padding: 0; }
.mock-row { display: flex; align-items: center; gap: 11px; padding: 11px 16px; border-bottom: 1px solid var(--line); font-size: 14px; }
.mock-row:last-child { border-bottom: none; }
.mock-row img { border-radius: 5px; }
.mock-generic-icon { width: 22px; height: 22px; border-radius: 5px; background: var(--line-strong); flex: none; }
.muted { color: var(--muted); }
.toggle { width: 32px; height: 20px; border-radius: 999px; margin-left: auto; position: relative; flex: none; }
.toggle.on  { background: #30d158; }
.toggle.off { background: var(--line-strong); }
.toggle::after {
  content: ""; position: absolute; top: 2px; width: 16px; height: 16px; border-radius: 50%;
  background: #fff; box-shadow: 0 1px 2px rgba(0,0,0,.2);
}
.toggle.on::after  { left: 14px; }
.toggle.off::after { left: 2px; }

/* ───────────────────────── FAQ ───────────────────────── */
.faq-list { margin-top: 24px; }
.faq-item {
  border-bottom: 1px solid var(--line); padding: 6px 0;
}
.faq-item summary {
  cursor: pointer; list-style: none; padding: 14px 0;
  font-size: 17px; font-weight: 500; display: flex; justify-content: space-between; align-items: center;
}
.faq-item summary::-webkit-details-marker { display: none; }
.faq-item summary::after {
  content: "+"; color: var(--muted); font-size: 22px; font-weight: 300; transition: transform .2s;
}
.faq-item[open] summary::after { content: "–"; }
.faq-item p { margin: 0 0 14px; color: var(--fg-soft); }

/* ───────────────────────── FOOTER ───────────────────────── */
.footer {
  text-align: center; padding: 40px 20px 56px;
  color: var(--muted); font-size: 14px; border-top: 1px solid var(--line);
}
.footer p { margin: 3px 0; }
.footer-sub { font-size: 12px; }

@media (max-width: 560px) {
  .nav-links { gap: 14px; }
  .nav-links a { font-size: 14px; }
  .step { grid-template-columns: 34px 1fr; gap: 12px; }
}

/* ───────────────────────── FEEDBACK WALL ───────────────────────── */
.fb-form {
  display: flex; flex-direction: column; gap: 10px;
  max-width: 560px; margin-top: 20px;
}
.fb-form input[type="text"],
.fb-form textarea {
  font: inherit; font-size: 15px; color: var(--fg);
  background: var(--bg-elev); border: 1px solid var(--line-strong);
  border-radius: 10px; padding: 11px 14px; width: 100%;
  resize: vertical;
}
.fb-form input:focus, .fb-form textarea:focus {
  outline: none; border-color: var(--accent);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--accent) 18%, transparent);
}
/* honeypot — visually hidden, still focusable-off-screen */
.hp {
  position: absolute; left: -9999px; width: 1px; height: 1px; opacity: 0; pointer-events: none;
}
.fb-captcha { min-height: 0; }
.fb-form-row { display: flex; align-items: center; justify-content: space-between; gap: 12px; }
.btn-small { padding: 8px 18px; font-size: 15px; }
.fb-status { font-size: 13px; color: var(--muted); min-height: 1em; }
.fb-status.ok { color: #1bbf5a; }
.fb-status.err { color: #e0404f; }

.fb-list { margin-top: 30px; display: flex; flex-direction: column; gap: 12px; }
.fb-item {
  background: var(--bg-elev); border: 1px solid var(--line);
  border-radius: 12px; padding: 14px 16px;
}
.fb-head { display: flex; align-items: baseline; gap: 10px; margin-bottom: 4px; }
.fb-name { font-weight: 600; font-size: 15px; }
.fb-time { font-size: 12px; color: var(--muted); margin-left: auto; }
.fb-message { margin: 2px 0 8px; white-space: pre-wrap; word-wrap: break-word; }
.fb-reply {
  display: flex; align-items: baseline; gap: 8px;
  margin: 6px 0 0; padding: 8px 12px;
  background: color-mix(in srgb, var(--accent) 8%, var(--bg));
  border-left: 3px solid var(--accent); border-radius: 6px; font-size: 14px;
}
.fb-badge {
  font-size: 11px; font-weight: 600; color: #fff;
  background: var(--accent); padding: 1px 7px; border-radius: 999px; flex: none;
}
.fb-reply-msg { flex: 1; white-space: pre-wrap; }
.fb-compose { display: flex; gap: 8px; margin-top: 10px; }
.fb-compose input {
  font: inherit; font-size: 14px; flex: 1;
  background: var(--bg); border: 1px solid var(--line-strong);
  border-radius: 8px; padding: 7px 11px; color: var(--fg);
}

/* ───────────────────────── SUPPORT / QR ───────────────────────── */
.qr-row { display: flex; flex-wrap: wrap; gap: 22px; margin-top: 24px; }
.qr-card {
  margin: 0; text-align: center;
  background: var(--bg-elev); border: 1px solid var(--line);
  border-radius: 14px; padding: 16px;
}
.qr-card img {
  width: 200px; height: 270px; object-fit: cover; border-radius: 10px;
  display: block; background: #fff;
}
.qr-card figcaption { margin-top: 10px; font-size: 14px; color: var(--fg-soft); }