:root {
  --bg: #fafaf7;
  --surface: #ffffff;
  --text: #1b1f24;
  --muted: #5b6470;
  --line: #e4e6ea;
  --accent: #2350d9;
  --accent-ink: #ffffff;
  --accent-soft: #eaf0ff;
  --ok: #137a3f;
  --err: #b3261e;
  --warn-bg: #fff6e0;
  --warn-line: #f0d48a;
  --radius: 14px;
  --font: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f1216;
    --surface: #171b21;
    --text: #eceff3;
    --muted: #9aa4b2;
    --line: #272d36;
    --accent: #7ea2ff;
    --accent-ink: #0b1226;
    --accent-soft: #1a2440;
    --ok: #5fd18b;
    --err: #ff8a80;
    --warn-bg: #2b2413;
    --warn-line: #5a4a1c;
  }
}

* { box-sizing: border-box; }
[hidden] { display: none !important; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  font-size: 17px;
  line-height: 1.6;
}
a { color: var(--accent); }
a:hover { text-decoration-thickness: 2px; }
img, svg { max-width: 100%; }

.wrap { width: 100%; max-width: 1040px; margin: 0 auto; padding: 0 20px; }
.narrow { max-width: 740px; }

/* header */
.site-header { border-bottom: 1px solid var(--line); background: var(--surface); }
.site-header .wrap { display: flex; align-items: center; justify-content: space-between; gap: 16px; min-height: 64px; flex-wrap: wrap; padding-top: 10px; padding-bottom: 10px; }
.brand { display: flex; align-items: center; gap: 10px; font-weight: 750; font-size: 1.15rem; color: var(--text); text-decoration: none; letter-spacing: -0.01em; }
.brand svg { width: 30px; height: 30px; flex: none; }
.nav { display: flex; gap: 4px 18px; flex-wrap: wrap; font-size: 0.95rem; }
.nav a { color: var(--muted); text-decoration: none; padding: 4px 0; }
.nav a:hover, .nav a[aria-current="page"] { color: var(--text); text-decoration: underline; text-underline-offset: 4px; }

/* buttons */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  background: var(--accent); color: var(--accent-ink);
  border: 0; border-radius: 12px; padding: 14px 22px;
  font: inherit; font-weight: 650; text-decoration: none; cursor: pointer;
}
.btn:hover { filter: brightness(1.06); }
.btn:disabled, .btn[aria-disabled="true"] { opacity: .5; cursor: not-allowed; }
.btn.secondary { background: var(--accent-soft); color: var(--accent); }
.btn.small { padding: 8px 14px; font-size: 0.92rem; border-radius: 10px; }

/* hero */
.hero { padding: 64px 0 40px; }
.hero h1 { font-size: clamp(2rem, 5vw, 3.1rem); line-height: 1.12; letter-spacing: -0.02em; margin: 0 0 16px; max-width: 16em; }
.hero p.lead { font-size: 1.2rem; color: var(--muted); max-width: 34em; margin: 0 0 26px; }
.hero .cta-row { display: flex; gap: 14px; align-items: center; flex-wrap: wrap; }
.hero .cta-note { color: var(--muted); font-size: 0.95rem; }

/* sections */
section { padding: 34px 0; }
h2 { font-size: 1.6rem; letter-spacing: -0.01em; margin: 0 0 14px; line-height: 1.25; }
h3 { font-size: 1.15rem; margin: 22px 0 6px; }
.cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 16px; }
.card { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 22px; }
.card h3 { margin-top: 0; }
.card p { margin: 0; color: var(--muted); }
.steps { counter-reset: s; list-style: none; padding: 0; margin: 0; display: grid; gap: 14px; }
.steps li { counter-increment: s; display: flex; gap: 14px; align-items: flex-start; }
.steps li::before { content: counter(s); flex: none; width: 32px; height: 32px; border-radius: 50%; background: var(--accent-soft); color: var(--accent); display: grid; place-items: center; font-weight: 700; }

.notice { background: var(--warn-bg); border: 1px solid var(--warn-line); border-radius: var(--radius); padding: 18px 20px; }
.notice p { margin: 0; }
.notice p + p { margin-top: 8px; }

/* article pages */
.article { padding: 44px 0 30px; }
.article h1 { font-size: clamp(1.8rem, 4.5vw, 2.5rem); line-height: 1.15; letter-spacing: -0.02em; margin: 0 0 14px; }
.article .lead { font-size: 1.15rem; color: var(--muted); margin: 0 0 24px; }
.article p, .article li { max-width: 46em; }
.article ol, .article ul { padding-left: 1.3em; }
.article li { margin: 6px 0; }
.callout { background: var(--accent-soft); border-radius: var(--radius); padding: 20px 22px; margin: 26px 0; display: flex; gap: 16px; align-items: center; justify-content: space-between; flex-wrap: wrap; }
.callout p { margin: 0; font-weight: 600; max-width: 30em; }

details { background: var(--surface); border: 1px solid var(--line); border-radius: 12px; padding: 4px 18px; margin: 10px 0; }
summary { cursor: pointer; font-weight: 650; padding: 12px 0; }
details p { margin: 0 0 14px; color: var(--muted); }

/* converter */
.tool { padding: 40px 0 10px; }
.tool h1 { font-size: clamp(1.8rem, 4.5vw, 2.5rem); line-height: 1.15; letter-spacing: -0.02em; margin: 0 0 8px; }
.tool .lead { color: var(--muted); margin: 0 0 22px; font-size: 1.1rem; }
.engine { display: flex; align-items: center; gap: 12px; background: var(--surface); border: 1px solid var(--line); border-radius: 12px; padding: 12px 16px; margin-bottom: 14px; font-size: 0.95rem; }
.engine .dot { width: 12px; height: 12px; border-radius: 50%; background: var(--muted); flex: none; }
.engine[data-state="loading"] .dot { background: var(--accent); animation: pulse 1.2s ease-in-out infinite; }
.engine[data-state="ready"] .dot { background: var(--ok); }
.engine[data-state="error"] .dot { background: var(--err); }
@keyframes pulse { 0%,100% { opacity: .35; } 50% { opacity: 1; } }
@media (prefers-reduced-motion: reduce) { .engine[data-state="loading"] .dot { animation: none; } }

.drop {
  display: block; text-align: center; cursor: pointer;
  border: 2px dashed var(--line); border-radius: var(--radius);
  background: var(--surface); padding: 46px 20px;
  transition: border-color .15s, background .15s;
}
.drop:hover, .drop.over { border-color: var(--accent); background: var(--accent-soft); }
.drop strong { display: block; font-size: 1.25rem; margin-bottom: 4px; }
.drop span { color: var(--muted); }
.drop input { position: absolute; width: 1px; height: 1px; opacity: 0; }
.drop:focus-within { outline: 3px solid var(--accent); outline-offset: 2px; }

.msg { margin: 12px 0 0; color: var(--err); font-weight: 600; min-height: 1.4em; }
.files { list-style: none; margin: 16px 0 0; padding: 0; display: grid; gap: 10px; }
.file { display: flex; align-items: center; gap: 14px; background: var(--surface); border: 1px solid var(--line); border-radius: 12px; padding: 12px 16px; flex-wrap: wrap; }
.file .name { flex: 1 1 220px; min-width: 0; overflow-wrap: anywhere; font-weight: 600; }
.file .state { color: var(--muted); font-size: 0.93rem; }
.file .state.ok { color: var(--ok); font-weight: 650; }
.file .state.bad { color: var(--err); font-weight: 650; }
.file .actions { display: flex; gap: 8px; flex-wrap: wrap; }
.toolbar { display: flex; justify-content: flex-end; margin-top: 14px; }
.privacy-line { color: var(--muted); font-size: 0.95rem; margin-top: 18px; }

/* footer */
.site-footer { border-top: 1px solid var(--line); margin-top: 50px; padding: 30px 0 44px; color: var(--muted); font-size: 0.9rem; background: var(--surface); }
.site-footer a { color: var(--muted); }
.site-footer .links { display: flex; gap: 6px 18px; flex-wrap: wrap; margin-bottom: 12px; }
.site-footer p { margin: 6px 0; max-width: 60em; }

@media (max-width: 560px) {
  body { font-size: 16.5px; }
  .hero { padding-top: 40px; }
  .drop { padding: 34px 16px; }
}