:root {
  color-scheme: light;
  --sky-top: #F4F7FC;
  --sky-bottom: #DCEBFB;
  --blue-1: #9CC8FB;
  --blue-2: #4F8FEA;
  --blue-3: #2F6FD6;
  --ink: #0E1116;
  --muted: #5B6472;
  --line: #E6EAF0;
  --sheet: #FFFFFF;
  --ok: #1F9D55;
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  min-height: 100vh;
  background: linear-gradient(180deg, var(--sky-top) 0%, var(--sky-bottom) 100%) fixed;
  color: var(--ink);
  font: 16px/1.6 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}

a { color: var(--blue-3); }

.wrap { max-width: 880px; margin: 0 auto; padding: 0 16px; }

header.top {
  display: flex; align-items: center; justify-content: space-between;
  padding: 20px 0;
}
.brand { display: flex; align-items: center; gap: 10px; font-weight: 800; font-size: 20px; color: var(--ink); text-decoration: none; }
.ball {
  width: 34px; height: 34px; border-radius: 50%; position: relative; flex: none;
  background: radial-gradient(circle at 35% 30%, var(--blue-1), var(--blue-2) 55%, var(--blue-3));
  box-shadow: 0 4px 12px rgba(47, 111, 214, .35);
}
.ball::before, .ball::after {
  content: ""; position: absolute; top: 11px; width: 4px; height: 10px; border-radius: 3px; background: #fff;
}
.ball::before { left: 11px; transform: rotate(-8deg); }
.ball::after { right: 11px; transform: rotate(8deg); }
nav.links { display: flex; gap: 18px; font-size: 15px; }
nav.links a { color: var(--muted); text-decoration: none; }
nav.links a:hover { color: var(--ink); }

.sheet {
  background: var(--sheet);
  border-radius: 32px;
  padding: 32px 28px;
  box-shadow: 0 10px 40px rgba(31, 60, 110, .08);
  margin: 12px 0 28px;
}

h1 { font-size: clamp(32px, 6vw, 48px); line-height: 1.1; margin: 0 0 14px; letter-spacing: -0.02em; }
h2 { font-size: 22px; margin: 32px 0 10px; }
h3 { font-size: 17px; margin: 20px 0 6px; }
p.lead { font-size: 19px; color: var(--muted); margin: 0 0 24px; max-width: 34em; }
.muted { color: var(--muted); }

.pill {
  display: inline-flex; align-items: center; gap: 8px;
  background: var(--ink); color: #fff; text-decoration: none;
  padding: 14px 24px; border-radius: 999px; font-weight: 700;
}
.pill.light { background: #fff; color: var(--ink); border: 1px solid var(--line); }
.row { display: flex; flex-wrap: wrap; gap: 12px; align-items: center; }

/* hero */
.hero { display: grid; grid-template-columns: 1.1fr .9fr; gap: 28px; align-items: center; }
@media (max-width: 760px) { .hero { grid-template-columns: 1fr; } }
.demo { background: var(--sky-top); border-radius: 24px; padding: 20px; }
.demo .problem { font-family: "Times New Roman", Georgia, serif; font-size: 22px; font-style: italic; text-align: center; padding: 6px 0 14px; }
.step {
  display: flex; align-items: center; gap: 10px; background: #fff; border-radius: 16px;
  padding: 10px 14px; margin-top: 8px; font-family: "Times New Roman", Georgia, serif; font-size: 18px;
}
.step .eq { flex: 1; font-style: italic; }
.check {
  flex: none; width: 22px; height: 22px; border-radius: 50%; background: var(--blue-3); color: #fff;
  display: grid; place-items: center; font: 700 13px/1 -apple-system, sans-serif;
}
.step.answer { outline: 2px solid var(--blue-1); }

.features { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
@media (max-width: 760px) { .features { grid-template-columns: 1fr; } }
.feature { background: var(--sky-top); border-radius: 24px; padding: 20px; }
.feature h3 { margin-top: 0; }
.feature p { margin: 0; color: var(--muted); font-size: 15px; }

/* documents */
.doc h1 { font-size: clamp(28px, 5vw, 38px); }
.doc table { width: 100%; border-collapse: collapse; font-size: 14.5px; margin: 8px 0 4px; }
.doc th, .doc td { text-align: left; vertical-align: top; padding: 10px 10px 10px 0; border-bottom: 1px solid var(--line); }
.doc th { font-size: 13px; text-transform: uppercase; letter-spacing: .04em; color: var(--muted); }
.table-scroll { overflow-x: auto; }
.doc ul, .doc ol { padding-left: 22px; }
.doc li { margin: 6px 0; }
.callout { background: var(--sky-top); border-radius: 20px; padding: 16px 20px; margin: 16px 0; }

footer { padding: 8px 0 40px; font-size: 14px; color: var(--muted); }
footer .row { justify-content: space-between; }
footer a { color: var(--muted); }