:root {
  --bg: #f7f8fb;
  --surface: #ffffff;
  --ink: #1b2236;
  --muted: #5b6478;
  --brand: #2f5bea;
  --brand-dark: #2447bd;
  --accent: #e8eefc;
  --line: #dde2ee;
  --ok: #eaf6ee;
  --ok-line: #9ad1ab;
  --bad: #fdeeee;
  --bad-line: #e5a1a1;
  --radius: 12px;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.65;
  font-size: 17px;
}
a { color: var(--brand); }
a:hover { color: var(--brand-dark); }
.wrap { max-width: 880px; margin: 0 auto; padding: 0 18px; }

header.site {
  background: var(--surface);
  border-bottom: 1px solid var(--line);
}
header.site .wrap {
  display: flex; align-items: center; justify-content: space-between;
  flex-wrap: wrap; gap: 8px; padding-top: 14px; padding-bottom: 14px;
}
.logo { font-weight: 800; font-size: 1.15rem; color: var(--ink); text-decoration: none; letter-spacing: -0.01em; }
.logo span { color: var(--brand); }
nav a { margin-left: 16px; text-decoration: none; color: var(--muted); font-size: 0.95rem; }
nav a:hover { color: var(--brand); }

.hero { padding: 34px 0 10px; }
h1 { font-size: clamp(1.7rem, 4.5vw, 2.35rem); line-height: 1.2; margin: 0 0 10px; letter-spacing: -0.02em; }
.lead { color: var(--muted); font-size: 1.08rem; margin: 0 0 8px; }

.card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 22px;
  margin: 18px 0 28px;
  box-shadow: 0 2px 10px rgba(30, 45, 90, 0.05);
}
[role="tablist"] { display: flex; gap: 6px; flex-wrap: wrap; margin-bottom: 16px; }
[role="tab"] {
  font: inherit; font-size: 0.95rem; cursor: pointer;
  padding: 9px 14px; border-radius: 8px;
  border: 1px solid var(--line); background: var(--bg); color: var(--ink);
}
[role="tab"][aria-selected="true"] { background: var(--brand); border-color: var(--brand); color: #fff; }
[role="tab"]:focus-visible, button:focus-visible, input:focus-visible { outline: 3px solid #9bb4ff; outline-offset: 2px; }

.row { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; margin: 12px 0; }
.row .sep { font-weight: 700; font-size: 1.3rem; color: var(--muted); }
label.field { display: flex; flex-direction: column; font-size: 0.85rem; color: var(--muted); gap: 4px; }
input[type="text"], input[type="number"] {
  font: inherit; width: 110px; padding: 10px 12px;
  border: 1px solid var(--line); border-radius: 8px; background: #fff; color: var(--ink);
}
.hint { font-size: 0.92rem; color: var(--muted); margin: 6px 0 4px; }
.actions { display: flex; gap: 10px; margin-top: 14px; }
button.primary, button.ghost {
  font: inherit; cursor: pointer; padding: 10px 20px; border-radius: 8px; border: 1px solid var(--brand);
}
button.primary { background: var(--brand); color: #fff; font-weight: 600; }
button.primary:hover { background: var(--brand-dark); }
button.ghost { background: #fff; color: var(--brand); }

.result { margin-top: 16px; border-radius: 10px; }
.result-ok, .result-error { padding: 14px 16px; }
.result-ok { background: var(--ok); border: 1px solid var(--ok-line); }
.result-error { background: var(--bad); border: 1px solid var(--bad-line); }
.result p { margin: 4px 0; }
.big { font-size: 1.6rem; font-weight: 800; letter-spacing: -0.01em; }
.muted { color: var(--muted); font-size: 0.93rem; }
table.mini { border-collapse: collapse; margin: 8px 0; min-width: 260px; }
table.mini th, table.mini td { border: 1px solid var(--ok-line); padding: 6px 12px; text-align: left; }

main h2 { font-size: 1.5rem; margin: 38px 0 10px; letter-spacing: -0.01em; line-height: 1.3; }
main h3 { font-size: 1.15rem; margin: 24px 0 6px; }
main p, main li { max-width: 72ch; }
.example {
  background: var(--accent); border-left: 4px solid var(--brand);
  padding: 12px 16px; border-radius: 0 8px 8px 0; margin: 14px 0;
}
table.data { border-collapse: collapse; width: 100%; background: var(--surface); margin: 12px 0; font-size: 0.97rem; }
table.data th, table.data td { border: 1px solid var(--line); padding: 8px 12px; text-align: left; }
table.data th { background: var(--accent); }
details {
  background: var(--surface); border: 1px solid var(--line);
  border-radius: 10px; padding: 12px 16px; margin: 10px 0;
}
summary { cursor: pointer; font-weight: 600; }
details[open] summary { margin-bottom: 6px; }

footer.site { margin-top: 50px; border-top: 1px solid var(--line); background: var(--surface); padding: 24px 0; color: var(--muted); font-size: 0.92rem; }
footer.site a { margin-right: 14px; }

@media (max-width: 520px) {
  input[type="text"], input[type="number"] { width: 84px; }
  .card { padding: 16px; }
}