/* solvup.app — one stylesheet for the Korean and English pages. Colours follow the app
   (solver-app src/index.css): light by default, dark when the system asks for it. */
:root {
  --bg: #eef1f4;
  --surf: #ffffff;
  --line: #dce2ea;
  --txt: #17202b;
  --txt2: #3c4756;
  --muted: #667283;
  --acc: #2447d6;
  --acch: #1b37aa;
  --onacc: #ffffff;
  --accsoft: #e6ebfb;
  --good: #11795d;
  --shadow: 0 1px 2px rgba(23, 32, 43, 0.06), 0 12px 32px rgba(23, 32, 43, 0.08);
  --radius: 16px;
  --wrap: 1120px;
  --sans: "IBM Plex Sans KR", "Apple SD Gothic Neo", "Malgun Gothic", system-ui, sans-serif;
  --mono: "IBM Plex Mono", ui-monospace, monospace;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #141516;
    --surf: #1c1e20;
    --line: #2a2d30;
    --txt: #e6e7e8;
    --txt2: #c3c6ca;
    --muted: #8e959c;
    --acc: #7b93ff;
    --acch: #a1b3ff;
    --onacc: #0e1430;
    --accsoft: #1f2645;
    --good: #4cc79c;
    --shadow: 0 1px 2px rgba(0, 0, 0, 0.3), 0 12px 32px rgba(0, 0, 0, 0.35);
  }
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--txt);
  font-family: var(--sans);
  font-size: 17px;
  line-height: 1.7;
  word-break: keep-all;
  overflow-wrap: break-word;
}
img { max-width: 100%; height: auto; display: block; }
a { color: var(--acc); text-decoration: none; }
a:hover { color: var(--acch); }
.wrap { max-width: var(--wrap); margin: 0 auto; padding: 0 24px; }

/* Header */
header.top {
  position: sticky; top: 0; z-index: 10;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line);
}
header.top .wrap { display: flex; align-items: center; justify-content: space-between; height: 64px; gap: 16px; }
.brand { display: flex; align-items: center; gap: 10px; color: var(--txt); font-weight: 700; font-size: 20px; letter-spacing: -0.3px; }
.brand:hover { color: var(--txt); }
.brand svg { width: 30px; height: 30px; flex: none; }
nav.links { display: flex; align-items: center; gap: 22px; font-size: 15px; }
nav.links a { color: var(--txt2); }
nav.links a:hover { color: var(--acc); }
nav.links .lang { border: 1px solid var(--line); border-radius: 999px; padding: 4px 12px; color: var(--txt2); }

/* Hero */
.hero { padding: 72px 0 40px; }
.hero .wrap { display: grid; grid-template-columns: 1fr 1.15fr; gap: 48px; align-items: center; }
.badge {
  display: inline-flex; align-items: center; gap: 8px;
  background: var(--accsoft); color: var(--acc);
  border-radius: 999px; padding: 4px 14px; font-size: 14px; font-weight: 600;
}
.badge::before { content: ""; width: 7px; height: 7px; border-radius: 50%; background: var(--acc); }
h1 { font-size: clamp(34px, 4.4vw, 52px); line-height: 1.22; letter-spacing: -1.2px; margin: 18px 0 18px; }
h1 em { font-style: normal; color: var(--acc); }
.lead { font-size: clamp(17px, 2vw, 20px); color: var(--txt2); max-width: 640px; margin: 0 0 30px; }
.cta { display: flex; flex-wrap: wrap; gap: 12px; align-items: center; }
.btn {
  display: inline-flex; align-items: center; justify-content: center;
  min-height: 50px; padding: 0 24px; border-radius: 12px;
  font-weight: 700; font-size: 16px;
  background: var(--acc); color: var(--onacc);
}
.btn:hover { background: var(--acch); color: var(--onacc); }
.btn.ghost { background: transparent; color: var(--txt); border: 1px solid var(--line); }
.btn.ghost:hover { border-color: var(--acc); color: var(--acc); }
.note { font-size: 14px; color: var(--muted); }

/* Screens */
.screen {
  border-radius: var(--radius);
  border: 1px solid var(--line);
  background: var(--surf);
  box-shadow: var(--shadow);
  overflow: hidden;
}
.screen .bar { display: flex; gap: 6px; padding: 12px 14px; border-bottom: 1px solid var(--line); }
.screen .bar i { width: 10px; height: 10px; border-radius: 50%; background: var(--line); }
figure { margin: 0; }
figcaption { font-size: 14px; color: var(--muted); margin-top: 12px; text-align: center; }

/* Sections */
section { padding: 72px 0; }
section.alt { background: var(--surf); border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }
.eyebrow { color: var(--acc); font-weight: 700; font-size: 14px; letter-spacing: 0.5px; text-transform: uppercase; margin: 0 0 8px; }
h2 { font-size: clamp(26px, 3.4vw, 36px); line-height: 1.3; letter-spacing: -0.6px; margin: 0 0 14px; }
.sub { color: var(--txt2); max-width: 680px; margin: 0 0 40px; }

.steps { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; counter-reset: step; }
.step { background: var(--bg); border: 1px solid var(--line); border-radius: var(--radius); padding: 26px; }
section:not(.alt) .step { background: var(--surf); }
.step::before {
  counter-increment: step; content: counter(step);
  display: inline-flex; align-items: center; justify-content: center;
  width: 34px; height: 34px; border-radius: 10px;
  background: var(--accsoft); color: var(--acc); font-family: var(--mono); font-weight: 700;
}
.step h3 { font-size: 19px; margin: 16px 0 8px; letter-spacing: -0.3px; }
.step p { margin: 0; color: var(--txt2); font-size: 16px; }

.features { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px; }
.feature { border: 1px solid var(--line); border-radius: var(--radius); padding: 26px; background: var(--surf); }
section.alt .feature { background: var(--bg); }
.feature h3 { font-size: 19px; margin: 0 0 8px; letter-spacing: -0.3px; display: flex; gap: 10px; align-items: center; }
.feature h3 svg { width: 22px; height: 22px; color: var(--acc); flex: none; }
.feature p { margin: 0; color: var(--txt2); font-size: 16px; }

.split { display: grid; grid-template-columns: 1fr 1.25fr; gap: 48px; align-items: center; }
.sites { display: flex; flex-wrap: wrap; gap: 10px; margin: 18px 0 0; padding: 0; list-style: none; }
.sites li { border: 1px solid var(--line); border-radius: 999px; padding: 6px 14px; font-size: 15px; font-weight: 600; background: var(--surf); }
.sites li small { color: var(--muted); font-weight: 500; }

details { border-bottom: 1px solid var(--line); padding: 18px 0; }
details:first-of-type { border-top: 1px solid var(--line); }
summary { cursor: pointer; font-weight: 700; font-size: 18px; list-style: none; display: flex; justify-content: space-between; gap: 16px; }
summary::-webkit-details-marker { display: none; }
summary::after { content: "+"; color: var(--acc); font-family: var(--mono); font-size: 22px; line-height: 1; }
details[open] summary::after { content: "−"; }
details p { color: var(--txt2); margin: 12px 0 0; }

.final { text-align: center; }
.final .sub { margin-left: auto; margin-right: auto; }
.final .cta { justify-content: center; }

footer { padding: 36px 0 48px; color: var(--muted); font-size: 14px; }
footer .wrap { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 12px; }

@media (max-width: 860px) {
  .hero .wrap, .steps, .features, .split { grid-template-columns: 1fr; }
  nav.links a:not(.lang) { display: none; }
  .hero { padding-top: 48px; }
  section { padding: 56px 0; }
}
@media (max-width: 480px) {
  .wrap { padding: 0 16px; }
  .btn { width: 100%; }
}