/* SheldonTek: single static page. System fonts, no trackers, no build step. */
:root {
  --bg: #0b0f14;
  --bg-2: #10161d;
  --line: #1f2a35;
  --ink: #e8eef3;
  --muted: #9aa7b4;
  --accent: #3ee0b0;
  --accent-ink: #04140f;
  --max: 72rem;
  --sans: system-ui, -apple-system, "Segoe UI", "PingFang TC", "Microsoft JhengHei", "Noto Sans TC", sans-serif;
  --mono: ui-monospace, "SFMono-Regular", "Cascadia Mono", Consolas, "Liberation Mono", monospace;
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; scroll-padding-top: 4.5rem; }
body {
  margin: 0; background-color: var(--bg); color: var(--ink);
  font: 1.0625rem/1.65 var(--sans);
}
.gridbg { /* engineering-drawing grid, faded towards the bottom */
  position: fixed; inset: 0; z-index: -1; pointer-events: none;
  background-image:
    linear-gradient(rgba(62, 224, 176, .06) 1px, transparent 1px),
    linear-gradient(90deg, rgba(62, 224, 176, .06) 1px, transparent 1px);
  background-size: 64px 64px;
  -webkit-mask-image: radial-gradient(ellipse at 50% 0%, #000 0, transparent 75%);
  mask-image: radial-gradient(ellipse at 50% 0%, #000 0, transparent 75%);
}
a { color: var(--accent); text-underline-offset: .2em; }
a:hover { text-decoration-thickness: 2px; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; border-radius: 2px; }
.wrap { max-width: var(--max); margin: 0 auto; padding: 0 1.5rem; }
.skip { position: absolute; left: -999px; top: .5rem; background: var(--accent); color: var(--accent-ink); padding: .5rem 1rem; z-index: 10; }
.skip:focus { left: .5rem; }
.mono { font-family: var(--mono); letter-spacing: .02em; }

/* Header */
header { position: sticky; top: 0; z-index: 5; background: rgba(11, 15, 20, .9); -webkit-backdrop-filter: blur(8px); backdrop-filter: blur(8px); border-bottom: 1px solid var(--line); }
.bar { display: flex; align-items: center; gap: 1.5rem; height: 4rem; }
.brand { display: flex; align-items: center; gap: .6rem; color: var(--ink); text-decoration: none; font-weight: 700; letter-spacing: .01em; white-space: nowrap; }
.brand svg { flex: none; }
.brand small { font-weight: 400; color: var(--muted); font-size: .8rem; }
nav { margin-left: auto; }
nav ul { display: flex; gap: 1.25rem; list-style: none; margin: 0; padding: 0; }
nav a { color: var(--muted); text-decoration: none; font-size: .9rem; }
nav a:hover { color: var(--ink); }
.lang { display: flex; border: 1px solid var(--line); border-radius: .4rem; overflow: hidden; flex: none; }
.lang button { font: .8rem var(--mono); padding: .45rem .7rem; cursor: pointer; border: 0; background: transparent; color: var(--muted); }
.lang button[aria-pressed="true"] { background: var(--accent); color: var(--accent-ink); }

/* Hero */
.hero { position: relative; padding: 6.5rem 0 5.5rem; border-bottom: 1px solid var(--line); overflow: hidden; }
.hero canvas { position: absolute; inset: 0; width: 100%; height: 100%; }
.hero .wrap { position: relative; }
.eyebrow { font: .8rem var(--mono); color: var(--accent); text-transform: uppercase; letter-spacing: .12em; margin: 0 0 1.25rem; }
h1 { font-size: clamp(2rem, 5.5vw, 3.6rem); line-height: 1.1; letter-spacing: -.02em; margin: 0 0 1.25rem; max-width: 18ch; }
html[data-lang="zh"] h1 { max-width: 13em; letter-spacing: 0; line-height: 1.25; }
.lead { font-size: 1.2rem; color: var(--muted); max-width: 38rem; margin: 0 0 2rem; }
.cta { display: flex; flex-wrap: wrap; gap: .75rem; }
.btn { display: inline-block; padding: .8rem 1.3rem; border-radius: .4rem; font-weight: 600; text-decoration: none; border: 1px solid var(--accent); }
.btn.primary { background: var(--accent); color: var(--accent-ink); }
.btn.ghost { color: var(--ink); border-color: #3a4a5a; background: rgba(11, 15, 20, .7); }
.btn.ghost:hover { border-color: var(--muted); }
.meta { margin: 2.5rem 0 0; font: .78rem var(--mono); color: var(--muted); letter-spacing: .04em; }

/* Sections */
section.block { padding: 5rem 0; border-bottom: 1px solid var(--line); }
.sec-head { display: grid; grid-template-columns: 11rem 1fr; gap: 2rem; margin-bottom: 2.5rem; }
.idx { font: .8rem var(--mono); color: var(--accent); text-transform: uppercase; letter-spacing: .12em; padding-top: .55rem; }
h2 { font-size: clamp(1.5rem, 3vw, 2.1rem); line-height: 1.2; letter-spacing: -.01em; margin: 0 0 .5rem; }
.sec-head p { color: var(--muted); margin: 0; max-width: 40rem; }
h3 { font-size: 1.1rem; line-height: 1.35; margin: 0 0 .5rem; }
p { margin: 0 0 .9rem; }

/* Cards on a hairline grid */
.grid { display: grid; gap: 1px; background: var(--line); border: 1px solid var(--line); }
.g3 { grid-template-columns: repeat(3, 1fr); }
.g2 { grid-template-columns: repeat(2, 1fr); }
.card { background: var(--bg-2); padding: 1.75rem; min-width: 0; }
.card p { color: var(--muted); }
.k { font: .75rem var(--mono); color: var(--muted); letter-spacing: .08em; text-transform: uppercase; display: block; margin-bottom: 1rem; }
.k b { color: var(--accent); font-weight: 400; }
.deliv { list-style: none; padding: 0; margin: 1rem 0 0; font: .82rem/1.5 var(--mono); color: var(--ink); }
.deliv li { padding: .35rem 0; border-top: 1px dashed var(--line); }
.deliv li::before { content: "→ "; color: var(--accent); }
.tag { display: inline-block; font: .7rem var(--mono); padding: .1rem .5rem; border: 1px solid var(--accent); color: var(--accent); border-radius: 1rem; vertical-align: middle; margin-left: .4rem; text-transform: uppercase; letter-spacing: .06em; }
.links { margin: 1rem 0 0; font-size: .95rem; }
.links a { margin-right: 1rem; display: inline-block; }

/* Process */
.steps { list-style: none; margin: 0; padding: 0; display: grid; grid-template-columns: repeat(6, 1fr); gap: 1px; background: var(--line); border: 1px solid var(--line); counter-reset: s; }
.steps li { background: var(--bg-2); padding: 1.25rem; counter-increment: s; min-width: 0; }
.steps li::before { content: "0" counter(s); display: block; font: .8rem var(--mono); color: var(--accent); margin-bottom: .75rem; }
.steps b { display: block; margin-bottom: .35rem; }
.steps span { color: var(--muted); font-size: .9rem; }

/* Proof */
.stats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 1px; background: var(--line); border: 1px solid var(--line); }
.stat { background: var(--bg-2); padding: 1.75rem; min-width: 0; }
.stat .n { display: block; font: 600 2.4rem/1 var(--mono); color: var(--accent); margin-bottom: .75rem; }
.stat span { color: var(--muted); font-size: .92rem; }
.note { color: var(--muted); font-size: .9rem; margin-top: 1.25rem; }

/* Contact */
.contact { display: grid; grid-template-columns: 1fr 1fr; gap: 1px; background: var(--line); border: 1px solid var(--line); }
.contact > div { background: var(--bg-2); padding: 1.75rem; min-width: 0; }
.mail { font: 600 clamp(1.1rem, 3vw, 1.6rem) var(--mono); word-break: break-all; }
dl { margin: 0; }
dt { font: .75rem var(--mono); color: var(--muted); text-transform: uppercase; letter-spacing: .08em; margin-top: 1rem; }
dt:first-child { margin-top: 0; }
dd { margin: .25rem 0 0; }

footer { padding: 2rem 0 3rem; color: var(--muted); font-size: .85rem; }
footer p { margin: .25rem 0; }
footer .mono { font-size: .8rem; }

/* Responsive */
@media (max-width: 60rem) {
  nav { display: none; }
  .lang { margin-left: auto; }
  .g3 { grid-template-columns: 1fr 1fr; }
  .steps { grid-template-columns: repeat(3, 1fr); }
  .stats { grid-template-columns: 1fr 1fr; }
  .sec-head { grid-template-columns: 1fr; gap: .5rem; }
}
@media (max-width: 40rem) {
  .wrap { padding: 0 1.1rem; }
  .brand small { display: none; }
  .hero { padding: 4rem 0 3.5rem; }
  section.block { padding: 3.5rem 0; }
  .g3, .g2, .contact { grid-template-columns: 1fr; }
  .steps { grid-template-columns: 1fr 1fr; }
  .card, .stat, .contact > div { padding: 1.35rem; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
}

/* Language switching: English is shown by default (also when JS is off). */
[data-l="zh"] { display: none; }
html[data-lang="zh"] [data-l="zh"] { display: revert; }
html[data-lang="zh"] [data-l="en"] { display: none; }

/* Editorial hierarchy (refs: SpaceX full-bleed scale, Anthropic restraint).
   Latin headings use a system serif; CJK glyphs fall through to the sans fonts. */
:root { --serif: "Iowan Old Style", "Palatino Linotype", Palatino, "Book Antiqua", Georgia, "PingFang TC", "Microsoft JhengHei", "Noto Sans TC", serif; }
h1, h2 { font-family: var(--serif); font-weight: 500; }
.hero { min-height: min(88vh, 46rem); display: flex; align-items: center; }
.hero .wrap { width: 100%; }
h1 { font-size: clamp(2.3rem, 6.5vw, 4.6rem); }
.statement { padding: 7rem 0; border-bottom: 1px solid var(--line); background: linear-gradient(180deg, var(--bg) 0%, #0e1a1a 100%); }
.statement p { font: 400 clamp(1.5rem, 3.6vw, 2.6rem)/1.3 var(--serif); max-width: 22em; margin: 0; }
.statement em { font-style: normal; color: var(--accent); }
@media (max-width: 40rem) { .statement { padding: 4.5rem 0; } }