/* Monochrome (zinc) system: borders over shadows, rounded-md/lg, one solid CTA. */
:root {
  --zinc-50: #fafafa; --zinc-100: #f4f4f5; --zinc-200: #e4e4e7; --zinc-300: #d4d4d8;
  --zinc-400: #a1a1aa; --zinc-500: #71717a; --zinc-600: #52525b; --zinc-700: #3f3f46;
  --zinc-800: #27272a; --zinc-900: #18181b; --zinc-950: #09090b;

  --bg: #ffffff; --surface: var(--zinc-50); --text: var(--zinc-900); --text-2: var(--zinc-700);
  --muted: var(--zinc-500); --line: var(--zinc-100); --line-strong: var(--zinc-200); --line-hover: var(--zinc-300);
  --cta-bg: #000000; --cta-text: #ffffff;
  --ease: 200ms ease-in-out;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: var(--zinc-950); --surface: #111113; --text: var(--zinc-100); --text-2: var(--zinc-300);
    --muted: var(--zinc-400); --line: var(--zinc-800); --line-strong: var(--zinc-800); --line-hover: var(--zinc-600);
    --cta-bg: #ffffff; --cta-text: #000000;
  }
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0; background: var(--bg); color: var(--text-2);
  font: 16px/1.75 "SF Pro Text", -apple-system, BlinkMacSystemFont, system-ui, "Apple SD Gothic Neo", "Noto Sans KR", sans-serif;
  -webkit-font-smoothing: antialiased;
}
h1, h2, h3, strong, .brand { color: var(--text); }
h1, h2, h3 { letter-spacing: -0.025em; }
p, li, td, th { word-break: keep-all; overflow-wrap: anywhere; }
a { color: var(--text); text-decoration: underline; text-decoration-color: var(--line-hover);
    text-underline-offset: 3px; transition: all var(--ease); }
a:hover { text-decoration-color: currentColor; }
.wrap { max-width: 1040px; margin: 0 auto; padding: 0 16px; }
@media (min-width: 640px) { .wrap { padding: 0 32px; } }
.narrow { max-width: 760px; }

/* header */
header.site { border-bottom: 1px solid var(--line); background: var(--bg); }
header.site .wrap { display: flex; align-items: center; justify-content: space-between; gap: 16px; height: 64px; }
.brand { font-weight: 600; letter-spacing: -0.02em; text-decoration: none; white-space: nowrap; }
header.site nav { display: flex; gap: 4px; font-size: 14px; }
header.site nav a { color: var(--muted); text-decoration: none; padding: 6px 10px; border-radius: 6px; }
header.site nav a:hover { color: var(--text); background: var(--surface); }
header.site nav a[aria-current="page"] { color: var(--text); }
@media (max-width: 480px) { header.site nav a { padding: 6px 6px; font-size: 13px; } }

/* home */
.hero { padding: 120px 0 96px; }
@media (max-width: 640px) { .hero { padding: 72px 0 56px; } }
.eyebrow { color: var(--muted); font-size: 14px; font-weight: 500; margin: 0 0 20px; }
.hero h1 { font-size: clamp(36px, 6.5vw, 60px); line-height: 1.12; letter-spacing: -0.04em; font-weight: 700; margin: 0 0 24px; }
.lead { font-size: 18px; line-height: 1.7; color: var(--muted); max-width: 600px; margin: 0; }
.lead strong { font-weight: 600; }

.app { display: grid; grid-template-columns: 96px 1fr; gap: 32px; align-items: start;
       border: 1px solid var(--line-strong); border-radius: 8px; padding: 40px; margin: 0 0 96px;
       transition: border-color var(--ease); }
.app:hover { border-color: var(--line-hover); }
.app img { width: 96px; height: 96px; border-radius: 22px; }
.app h2 { margin: 0 0 4px; font-size: 28px; line-height: 1.2; }
.app .sub { color: var(--muted); margin: 0 0 20px; font-size: 15px; }
.app p { margin: 0 0 28px; max-width: 620px; }
@media (max-width: 640px) { .app { grid-template-columns: 1fr; padding: 28px 24px; gap: 20px; } .app img { width: 72px; height: 72px; border-radius: 16px; } }

.section-title { font-size: 14px; font-weight: 500; color: var(--muted); margin: 0 0 20px; letter-spacing: 0; }
.features { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
            border-top: 1px solid var(--line-strong); border-left: 1px solid var(--line-strong);
            border-radius: 8px; overflow: hidden; margin: 0 0 96px; }
.feature { padding: 28px; border-right: 1px solid var(--line-strong); border-bottom: 1px solid var(--line-strong);
           transition: background-color var(--ease); }
.feature:hover { background: var(--surface); }
.feature h3 { margin: 0 0 8px; font-size: 16px; font-weight: 600; }
.feature p { margin: 0; color: var(--muted); font-size: 15px; line-height: 1.65; }

.buttons { display: flex; flex-wrap: wrap; gap: 10px; }
.button { display: inline-flex; align-items: center; height: 40px; padding: 0 18px; border-radius: 6px;
          font-weight: 500; font-size: 14px; text-decoration: none; transition: all var(--ease);
          border: 1px solid var(--line-strong); color: var(--text); background: transparent; }
.button:hover { border-color: var(--line-hover); background: var(--surface); }
.button.primary { background: var(--cta-bg); color: var(--cta-text); border-color: var(--cta-bg); }
.button.primary:hover { opacity: 0.9; background: var(--cta-bg); }

section.block { margin: 0 0 120px; padding-top: 48px; border-top: 1px solid var(--line); }
section.block h2 { font-size: 24px; margin: 0 0 12px; }
section.block p { color: var(--muted); max-width: 600px; }

/* documents */
.doc { padding-top: 72px; padding-bottom: 120px; }
.doc h1 { font-size: clamp(30px, 5vw, 40px); line-height: 1.2; letter-spacing: -0.035em; margin: 0 0 10px; }
.meta { color: var(--muted); font-size: 14px; margin-bottom: 40px; }
.doc h2 { font-size: 20px; line-height: 1.4; margin: 56px 0 14px; padding-top: 32px; border-top: 1px solid var(--line); }
.doc h3 { font-size: 16px; margin: 28px 0 8px; }
ul, ol { padding-left: 22px; }
li { margin: 4px 0; }
.table { overflow-x: auto; margin: 16px 0; border: 1px solid var(--line-strong); border-radius: 8px; }
table { border-collapse: collapse; width: 100%; font-size: 14px; line-height: 1.6; }
th, td { border-bottom: 1px solid var(--line-strong); padding: 12px 14px; text-align: left; vertical-align: top; }
td + td, th + th { border-left: 1px solid var(--line-strong); }
tr:last-child td { border-bottom: 0; }
th { background: var(--surface); color: var(--text); font-weight: 600; white-space: nowrap; }
.toc { border: 1px solid var(--line-strong); border-radius: 8px; padding: 20px 24px; font-size: 14px; }
.toc ol { margin: 0; columns: 2; column-gap: 32px; }
.toc a { color: var(--muted); text-decoration: none; }
.toc a:hover { color: var(--text); }
@media (max-width: 560px) { .toc ol { columns: 1; } }
.note { border: 1px solid var(--line-strong); background: var(--surface); border-radius: 8px; padding: 20px 24px; font-size: 15px; }
details { border: 1px solid var(--line-strong); border-radius: 8px; padding: 0 20px; margin: 10px 0; transition: border-color var(--ease); }
details:hover, details[open] { border-color: var(--line-hover); }
details summary { cursor: pointer; font-weight: 500; color: var(--text); padding: 16px 0; list-style: none;
                  display: flex; justify-content: space-between; gap: 16px; }
details summary::-webkit-details-marker { display: none; }
details summary::after { content: "+"; color: var(--muted); font-weight: 400; transition: transform var(--ease); }
details[open] summary::after { transform: rotate(45deg); }
details p { margin: 0 0 18px; color: var(--muted); }

/* footer */
footer.site { border-top: 1px solid var(--line); padding: 40px 0 56px; font-size: 13px; color: var(--muted); }
footer.site .links { display: flex; flex-wrap: wrap; gap: 6px 20px; margin-bottom: 14px; }
footer.site .links a { color: var(--muted); text-decoration: none; }
footer.site .links a:hover { color: var(--text); }
footer.site .links a.strong { color: var(--text); font-weight: 600; }
footer.site p { margin: 2px 0; }
footer.site p a { color: var(--muted); }

/* app store button */
.button.store { gap: 8px; }
.button.store svg { margin-top: -2px; }

/* coming soon */
.soon { min-height: calc(100vh - 64px - 160px); display: flex; flex-direction: column; justify-content: center; padding: 96px 0; }
.soon img { width: 88px; height: 88px; border-radius: 20px; margin-bottom: 28px; }
.soon h1 { font-size: clamp(32px, 5.5vw, 48px); line-height: 1.15; letter-spacing: -0.04em; margin: 0 0 16px; }
.soon p { color: var(--muted); font-size: 17px; max-width: 520px; margin: 0 0 32px; }