/* ============================================================
   CoreInfra 基曜科技 — Design System
   Palette derived from the company logo:
   deep teal-navy ink + steel-blue ramp + cyan signal
   ============================================================ */

:root {
  /* ---- Brand: ink / navy ---- */
  --ink-900: #04161f;   /* deepest background */
  --ink-850: #061f2b;
  --ink-800: #082836;   /* dark section base */
  --ink-700: #0a3346;
  --navy:    #003048;   /* logo wordmark navy — primary */

  /* ---- Steel ramp (the metallic hexagon) ---- */
  --steel-700: #294453;
  --steel-600: #36586c;
  --steel-500: #4a627a;   /* logo steel */
  --steel-400: #647f99;
  --steel-300: #89a0b4;   /* logo steel-periwinkle */
  --steel-200: #b6c5d2;
  --steel-100: #d7e0e7;

  /* ---- Light surfaces ---- */
  --paper:  #f7fafb;
  --mist:   #eaeff3;
  --mist-2: #e1e8ed;
  --white:  #ffffff;
  --line:   #dde5eb;          /* hairline on light */
  --line-dk: rgba(137,160,180,0.16); /* hairline on dark */

  /* ---- Signal (cyan energy — server light) ---- */
  --signal:        #15a8c9;
  --signal-bright: #3ad6ef;
  --signal-deep:   #0e7e98;
  --signal-soft:   rgba(21,168,201,0.10);
  --signal-glow:   rgba(58,214,239,0.55);

  /* ---- Text ---- */
  --tx-dark:   #082836;   /* heading on light */
  --tx-body:   #46627a;   /* body on light */
  --tx-soft:   #6c8298;   /* muted on light */
  --tx-light:  #f1f6f9;   /* heading on dark */
  --tx-light-2: rgba(213,226,235,0.82); /* body on dark */
  --tx-light-3: rgba(176,196,210,0.62); /* muted on dark */

  /* ---- Type ---- */
  --f-display: 'Space Grotesk', 'Noto Sans TC', sans-serif;
  --f-body: 'Inter', 'Noto Sans TC', sans-serif;
  --f-cjk: 'Noto Sans TC', 'Inter', sans-serif;
  --f-mono: 'JetBrains Mono', ui-monospace, monospace;

  /* ---- Shape & motion ---- */
  --r-sm: 8px;
  --r: 12px;
  --r-lg: 18px;
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
  --shadow-sm: 0 2px 10px rgba(8,40,54,0.05);
  --shadow: 0 18px 50px -20px rgba(8,40,54,0.22);
  --shadow-lg: 0 40px 90px -36px rgba(4,22,31,0.45);
  --pad-x: 8.5vw;
}

* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }

body {
  font-family: var(--f-body);
  color: var(--tx-body);
  background: var(--white);
  line-height: 1.7;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
:lang(zh-TW) { letter-spacing: 0.01em; }

h1, h2, h3, h4 { font-family: var(--f-display); color: var(--tx-dark); line-height: 1.15; font-weight: 600; }
h1, h2 { letter-spacing: -0.02em; }
:lang(zh-TW) h1, :lang(zh-TW) h2, :lang(zh-TW) h3 { font-family: var(--f-cjk); font-weight: 900; letter-spacing: 0; }
strong { color: var(--tx-dark); font-weight: 600; }
a { color: inherit; }
img { max-width: 100%; display: block; }
::selection { background: var(--signal); color: #fff; }

/* ---------- Reusable layout ---------- */
.wrap { width: 100%; max-width: 1280px; margin: 0 auto; padding: 0 var(--pad-x); }
section { padding: clamp(72px, 11vh, 140px) 0; }
.eyebrow {
  font-family: var(--f-mono);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.26em;
  text-transform: uppercase;
  color: var(--signal-deep);
  display: inline-flex;
  align-items: center;
  gap: 12px;
}
.eyebrow::before {
  content: "";
  width: 26px; height: 1px;
  background: var(--signal);
  display: inline-block;
}
.eyebrow.on-dark { color: var(--signal-bright); }
.eyebrow.center { justify-content: center; }

.section-head { max-width: 760px; margin-bottom: clamp(40px, 6vh, 72px); }
.section-head.center { margin-left: auto; margin-right: auto; text-align: center; }
.section-head h2 {
  font-size: clamp(1.9rem, 4.2vw, 3rem);
  margin-top: 20px;
}
.section-head p {
  margin-top: 18px;
  font-size: 1.08rem;
  color: var(--tx-soft);
  max-width: 620px;
}
.section-head.center p { margin-left: auto; margin-right: auto; }

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex; align-items: center; gap: 10px;
  padding: 15px 30px;
  font-family: var(--f-body); font-weight: 600; font-size: 0.96rem;
  border-radius: 999px; border: 1px solid transparent;
  text-decoration: none; cursor: pointer;
  transition: transform .35s var(--ease), box-shadow .35s var(--ease), background .25s, color .25s, border-color .25s;
  position: relative;
}
.btn svg { width: 18px; height: 18px; }
.btn-primary {
  background: var(--signal); color: #00222b;
  box-shadow: 0 12px 30px -12px var(--signal-glow);
}
.btn-primary:hover { transform: translateY(-3px); box-shadow: 0 18px 40px -12px var(--signal-glow); background: var(--signal-bright); }
.btn-ghost {
  background: transparent; color: var(--tx-light);
  border-color: rgba(182,197,210,0.32);
}
.btn-ghost:hover { border-color: var(--signal-bright); color: var(--signal-bright); transform: translateY(-3px); }
.btn-dark { background: var(--navy); color: #fff; }
.btn-dark:hover { background: var(--ink-800); transform: translateY(-3px); box-shadow: var(--shadow); }
.btn-light { background: var(--tx-dark); color: #fff; }
.btn-light:hover { transform: translateY(-3px); box-shadow: var(--shadow); }

/* ---------- Navigation ---------- */
.site-nav {
  position: fixed; top: 0; left: 0; width: 100%; z-index: 1000;
  display: flex; align-items: center; justify-content: space-between;
  padding: 18px var(--pad-x);
  background: rgba(247,250,251,0);
  transition: padding .4s var(--ease), background .4s var(--ease), box-shadow .4s var(--ease), border-color .4s;
  border-bottom: 1px solid transparent;
}
.site-nav.scrolled {
  padding: 11px var(--pad-x);
  background: rgba(247,250,251,0.86);
  backdrop-filter: blur(16px) saturate(140%);
  -webkit-backdrop-filter: blur(16px) saturate(140%);
  border-bottom-color: var(--line);
  box-shadow: 0 8px 30px -18px rgba(8,40,54,0.3);
}
/* nav on dark hero before scroll */
.site-nav.on-hero:not(.scrolled) { border-bottom-color: var(--line-dk); }
.site-nav.on-hero:not(.scrolled) .brand-name { color: #fff; }
.site-nav.on-hero:not(.scrolled) .brand-sub { color: rgba(213,226,235,0.7); }
.site-nav.on-hero:not(.scrolled) .nav-links a { color: rgba(225,234,240,0.82); }
.site-nav.on-hero:not(.scrolled) .nav-links a:hover { color: #fff; }
.site-nav.on-hero:not(.scrolled) .menu-toggle span { background: #fff; }

.brand { display: flex; align-items: center; gap: 13px; text-decoration: none; }
.brand img { height: 46px; width: auto; transition: height .4s var(--ease); }
.site-nav.scrolled .brand img { height: 38px; }
.brand-text { display: flex; flex-direction: column; line-height: 1.05; }
.brand-name { font-family: var(--f-cjk); font-weight: 900; font-size: 1.18rem; color: var(--tx-dark); letter-spacing: 0.02em; transition: color .3s; }
.brand-sub { font-family: var(--f-mono); font-size: 0.66rem; font-weight: 500; letter-spacing: 0.22em; color: var(--tx-soft); margin-top: 3px; transition: color .3s; }

.nav-links { display: flex; align-items: center; gap: 34px; list-style: none; }
.nav-links a {
  text-decoration: none; color: var(--tx-body);
  font-size: 0.92rem; font-weight: 500; letter-spacing: 0.01em;
  position: relative; padding: 4px 0; transition: color .25s;
}
.nav-links a:not(.nav-lang)::after {
  content: ""; position: absolute; left: 0; bottom: -3px; height: 1.5px; width: 0;
  background: var(--signal); transition: width .3s var(--ease);
}
.nav-links a:not(.nav-lang):hover::after { width: 100%; }
.nav-links a:hover { color: var(--tx-dark); }
.nav-lang {
  font-family: var(--f-mono); font-size: 0.78rem; font-weight: 600; letter-spacing: 0.12em;
  padding: 7px 14px !important; border: 1px solid var(--line); border-radius: 999px;
  transition: border-color .25s, color .25s, background .25s;
}
.nav-lang:hover { border-color: var(--signal); color: var(--signal-deep); background: var(--signal-soft); }
.site-nav.on-hero:not(.scrolled) .nav-lang { border-color: rgba(182,197,210,0.32); color: #fff; }
.site-nav.on-hero:not(.scrolled) .nav-lang:hover { border-color: var(--signal-bright); color: var(--signal-bright); }

.menu-toggle { display: none; flex-direction: column; gap: 5px; cursor: pointer; padding: 6px; background: none; border: none; }
.menu-toggle span { width: 24px; height: 2px; background: var(--tx-dark); border-radius: 2px; transition: .3s var(--ease); }

/* ---------- Blueprint grid texture (for dark sections) ---------- */
.grid-tex {
  position: absolute; inset: 0; pointer-events: none;
  background-image:
    linear-gradient(var(--line-dk) 1px, transparent 1px),
    linear-gradient(90deg, var(--line-dk) 1px, transparent 1px);
  background-size: 64px 64px;
  -webkit-mask-image: radial-gradient(120% 100% at 50% 0%, #000 35%, transparent 78%);
          mask-image: radial-gradient(120% 100% at 50% 0%, #000 35%, transparent 78%);
}

/* ---------- Reveal animation ---------- */
.reveal { opacity: 0; transform: translateY(26px); transition: opacity .8s var(--ease), transform .8s var(--ease); }
.reveal.in { opacity: 1; transform: none; }
.reveal.d1 { transition-delay: .08s; }
.reveal.d2 { transition-delay: .16s; }
.reveal.d3 { transition-delay: .24s; }
.reveal.d4 { transition-delay: .32s; }
.reveal.d5 { transition-delay: .40s; }

@media (prefers-reduced-motion: reduce) {
  * { animation: none !important; }
  .reveal { opacity: 1; transform: none; transition: none; }
  html { scroll-behavior: auto; }
}

/* ---------- Footer ---------- */
.site-footer {
  position: relative; overflow: hidden;
  background: var(--ink-900); color: var(--tx-light-3);
  padding: 80px var(--pad-x) 40px;
}
.footer-top { display: flex; flex-wrap: wrap; gap: 50px; justify-content: space-between; align-items: flex-start; position: relative; z-index: 1; }
.footer-brand { max-width: 360px; }
.footer-brand .fb-name { font-family: var(--f-cjk); font-weight: 900; font-size: 1.3rem; color: var(--tx-light); margin-bottom: 6px; }
.footer-brand .fb-sub { font-family: var(--f-mono); font-size: 0.7rem; letter-spacing: 0.2em; color: var(--signal-bright); margin-bottom: 18px; }
.footer-brand p { font-size: 0.92rem; color: var(--tx-light-3); line-height: 1.7; }
.footer-cols { display: flex; gap: 64px; flex-wrap: wrap; }
.footer-col h5 { font-family: var(--f-mono); font-size: 0.68rem; letter-spacing: 0.2em; text-transform: uppercase; color: var(--tx-light-3); margin-bottom: 16px; font-weight: 600; }
.footer-col a { display: block; text-decoration: none; color: var(--tx-light-2); font-size: 0.92rem; padding: 6px 0; transition: color .25s, transform .25s; }
.footer-col a:hover { color: var(--signal-bright); transform: translateX(4px); }
.footer-bottom {
  margin-top: 56px; padding-top: 26px; border-top: 1px solid var(--line-dk);
  display: flex; flex-wrap: wrap; gap: 12px; justify-content: space-between;
  font-size: 0.82rem; color: var(--tx-light-3); position: relative; z-index: 1;
}

/* ---------- Responsive ---------- */
@media (max-width: 880px) {
  :root { --pad-x: 6%; }
  .menu-toggle { display: flex; }
  .nav-links {
    position: absolute; top: 100%; left: 0; width: 100%;
    flex-direction: column; align-items: stretch; gap: 0;
    background: rgba(247,250,251,0.98); backdrop-filter: blur(18px);
    padding: 8px 6% 18px; border-bottom: 1px solid var(--line);
    box-shadow: 0 20px 40px -20px rgba(8,40,54,0.25);
    clip-path: inset(0 0 100% 0); transition: clip-path .4s var(--ease);
  }
  .nav-links.open { clip-path: inset(0 0 0 0); }
  .nav-links a { padding: 14px 4px; border-bottom: 1px solid var(--line); color: var(--tx-body) !important; }
  .nav-links a::after { display: none; }
  .nav-lang { border: none !important; padding: 14px 4px !important; color: var(--signal-deep) !important; }
  .footer-top { flex-direction: column; gap: 40px; }
  .footer-cols { gap: 40px; }
}

/* ============================================================
   SERVICE / INNER PAGES
   ============================================================ */
.svc-hero {
  position: relative; overflow: hidden; isolation: isolate;
  background: var(--ink-900); color: var(--tx-light);
  padding: clamp(140px, 20vh, 200px) 0 clamp(56px, 8vh, 92px);
}
.svc-hero .grid-tex { opacity: 0.55; }
.svc-hero .sh-glow {
  position: absolute; z-index: 0; right: -10%; top: -20%;
  width: 50vw; height: 50vw; max-width: 620px; max-height: 620px;
  background: radial-gradient(circle, var(--signal-glow) 0%, transparent 62%);
  opacity: 0.32; filter: blur(10px); pointer-events: none;
}
.svc-hero .ghost-num {
  position: absolute; z-index: 0; right: 4vw; top: 50%; transform: translateY(-46%);
  font-family: var(--f-display); font-weight: 700; font-size: clamp(10rem, 26vw, 22rem);
  color: rgba(137,160,180,0.06); line-height: 0.8; pointer-events: none; user-select: none;
}
.svc-hero .inner { position: relative; z-index: 2; }
.crumb { font-family: var(--f-mono); font-size: 0.72rem; letter-spacing: 0.14em; color: var(--tx-light-3); display: flex; gap: 10px; align-items: center; }
.crumb a { color: var(--tx-light-3); text-decoration: none; transition: color .25s; }
.crumb a:hover { color: var(--signal-bright); }
.crumb .sep { color: var(--steel-500); }
.crumb .cur { color: var(--signal-bright); }
.svc-hero h1 { color: #fff; font-size: clamp(2rem, 5vw, 3.4rem); margin: 22px 0 0; max-width: 18ch; }
.svc-hero .sh-sub { font-family: var(--f-mono); font-size: 0.86rem; letter-spacing: 0.16em; color: var(--steel-300); text-transform: uppercase; margin-top: 16px; }
.svc-hero .sh-intro { color: var(--tx-light-2); font-size: 1.08rem; max-width: 60ch; margin-top: 24px; line-height: 1.85; }

/* phase rail in inner hero */
.phase-rail { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 40px; }
.phase-rail .pr {
  display: flex; align-items: center; gap: 9px;
  font-family: var(--f-mono); font-size: 0.74rem; letter-spacing: 0.04em;
  padding: 9px 15px; border-radius: 999px; border: 1px solid var(--line-dk);
  color: var(--tx-light-3); text-decoration: none; transition: .3s;
}
.phase-rail .pr .dot { width: 7px; height: 7px; border-radius: 50%; background: var(--steel-500); }
.phase-rail .pr:hover { border-color: rgba(58,214,239,0.4); color: var(--tx-light-2); }
.phase-rail .pr.cur { background: var(--signal-soft); border-color: var(--signal); color: #fff; }
.phase-rail .pr.cur .dot { background: var(--signal-bright); box-shadow: 0 0 10px var(--signal-glow); }

/* content blocks */
.svc-content { background: var(--paper); }
.lead-row { max-width: 820px; margin: 0 auto clamp(40px,6vh,72px); text-align: center; }
.lead-row h2 { font-size: clamp(1.5rem, 3.2vw, 2.1rem); }
.lead-row p { margin-top: 18px; color: var(--tx-soft); font-size: 1.06rem; }

.feature-list { display: flex; flex-direction: column; gap: 18px; }
.feature-row {
  display: grid; grid-template-columns: auto 1fr; gap: 26px; align-items: flex-start;
  background: var(--white); border: 1px solid var(--line); border-radius: var(--r);
  padding: 30px 34px; box-shadow: var(--shadow-sm); transition: transform .4s var(--ease), box-shadow .4s, border-color .3s;
}
.feature-row:hover { transform: translateY(-4px); box-shadow: var(--shadow); border-color: var(--steel-200); }
.feature-row .fr-ico {
  width: 56px; height: 56px; border-radius: 13px; flex-shrink: 0;
  background: var(--signal-soft); border: 1px solid rgba(21,168,201,0.18);
  display: flex; align-items: center; justify-content: center; position: relative;
}
.feature-row .fr-ico svg { width: 27px; height: 27px; stroke: var(--signal-deep); fill: none; stroke-width: 1.6; }
.feature-row .fr-ico .fr-n { position: absolute; top: -10px; left: -10px; width: 26px; height: 26px; border-radius: 50%; background: var(--navy); color: #fff; font-family: var(--f-mono); font-size: 0.72rem; font-weight: 600; display: flex; align-items: center; justify-content: center; }
.feature-row h3 { font-size: 1.22rem; margin-bottom: 8px; }
.feature-row p { color: var(--tx-body); font-size: 0.98rem; }

/* two-column card grid */
.card-2 { display: grid; grid-template-columns: 1fr 1fr; gap: 18px; }
.s-card {
  background: var(--white); border: 1px solid var(--line); border-radius: var(--r);
  padding: 34px; box-shadow: var(--shadow-sm); transition: transform .4s var(--ease), box-shadow .4s;
}
.s-card:hover { transform: translateY(-4px); box-shadow: var(--shadow); }
.s-card h3 { font-size: 1.18rem; margin-bottom: 16px; display: flex; align-items: center; gap: 10px; }
.s-card h3 svg { width: 22px; height: 22px; stroke: var(--signal-deep); fill: none; stroke-width: 1.6; }
.s-card ul { list-style: none; }
.s-card li { position: relative; padding: 8px 0 8px 26px; color: var(--tx-body); font-size: 0.96rem; border-bottom: 1px solid var(--line); }
.s-card li:last-child { border-bottom: none; }
.s-card li::before { content: ""; position: absolute; left: 4px; top: 16px; width: 7px; height: 7px; border-radius: 2px; background: var(--signal); transform: rotate(45deg); }

/* pull quote / commitment */
.pull {
  position: relative; overflow: hidden;
  background: linear-gradient(135deg, var(--ink-800), var(--navy));
  color: #fff; border-radius: var(--r-lg); padding: clamp(36px,5vw,56px);
  text-align: center;
}
.pull .grid-tex { opacity: 0.4; }
.pull .pk { font-family: var(--f-mono); font-size: 0.7rem; letter-spacing: 0.2em; color: var(--signal-bright); text-transform: uppercase; position: relative; }
.pull .pq { font-family: var(--f-cjk); font-weight: 900; font-size: clamp(1.3rem, 3vw, 2rem); margin-top: 16px; position: relative; line-height: 1.5; }
.pull .ps { color: var(--tx-light-2); font-size: 1rem; margin-top: 16px; position: relative; max-width: 60ch; margin-left: auto; margin-right: auto; }

/* CX L1-L5 step ladder */
.ladder { display: grid; grid-template-columns: repeat(5, 1fr); gap: 14px; }
.ladder .rung {
  background: var(--white); border: 1px solid var(--line); border-top: 3px solid var(--signal);
  border-radius: var(--r); padding: 24px 20px; box-shadow: var(--shadow-sm);
  position: relative; transition: transform .4s var(--ease), box-shadow .4s;
}
.ladder .rung:hover { transform: translateY(-5px); box-shadow: var(--shadow); }
.ladder .rung .lv { font-family: var(--f-mono); font-weight: 600; font-size: 0.9rem; color: var(--signal-deep); letter-spacing: 0.06em; }
.ladder .rung h4 { font-size: 1.06rem; margin: 8px 0 10px; }
.ladder .rung p { font-size: 0.86rem; color: var(--tx-soft); line-height: 1.6; }

/* media block (image / video) */
.media-block { border-radius: var(--r-lg); overflow: hidden; box-shadow: var(--shadow); border: 1px solid var(--line); background: #000; }
.media-block img, .media-block video { width: 100%; height: auto; display: block; }
.media-cap { text-align: center; font-family: var(--f-mono); font-size: 0.76rem; letter-spacing: 0.08em; color: var(--tx-soft); margin-top: 16px; }
.media-frame { background: var(--white); border: 1px solid var(--line); border-radius: var(--r-lg); padding: 14px; box-shadow: var(--shadow); }
.media-frame video, .media-frame img { border-radius: 10px; width: 100%; display: block; }

/* retrofit dark band */
.dark-band { position: relative; overflow: hidden; background: var(--ink-850); color: var(--tx-light); border-radius: var(--r-lg); padding: clamp(36px,5vw,56px); }
.dark-band .grid-tex { opacity: 0.5; }
.dark-band > * { position: relative; z-index: 1; }
.dark-band h3 { color: #fff; }
.trio { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; margin-top: 30px; }
.trio .t-item { background: rgba(10,51,70,0.4); border: 1px solid var(--line-dk); border-radius: var(--r); padding: 28px 24px; transition: .35s; }
.trio .t-item:hover { border-color: rgba(58,214,239,0.4); transform: translateY(-4px); }
.trio .t-ico { width: 46px; height: 46px; border-radius: 11px; background: var(--signal-soft); display: flex; align-items: center; justify-content: center; margin-bottom: 16px; }
.trio .t-ico svg { width: 24px; height: 24px; stroke: var(--signal-bright); fill: none; stroke-width: 1.6; }
.trio h4 { color: #fff; font-size: 1.06rem; margin-bottom: 8px; }
.trio p { color: var(--tx-light-3); font-size: 0.88rem; }

/* page prev/next nav */
.page-nav { display: grid; grid-template-columns: 1fr auto 1fr; gap: 14px; align-items: center; margin-top: clamp(48px,7vh,80px); }
.page-nav .pg {
  display: inline-flex; align-items: center; gap: 12px; text-decoration: none;
  padding: 18px 24px; border-radius: var(--r); border: 1px solid var(--line);
  background: var(--white); transition: .35s var(--ease); box-shadow: var(--shadow-sm);
}
.page-nav .pg:hover { border-color: var(--signal); transform: translateY(-3px); box-shadow: var(--shadow); }
.page-nav .pg .pg-k { font-family: var(--f-mono); font-size: 0.66rem; letter-spacing: 0.14em; text-transform: uppercase; color: var(--tx-soft); display: block; }
.page-nav .pg .pg-t { font-family: var(--f-cjk); font-weight: 700; color: var(--tx-dark); font-size: 0.98rem; margin-top: 3px; }
.page-nav .pg.next { justify-content: flex-end; text-align: right; }
.page-nav .pg.home { padding: 16px 22px; }
.page-nav .pg-mid { font-family: var(--f-mono); font-size: 0.72rem; color: var(--tx-soft); text-decoration: none; letter-spacing: 0.08em; white-space: nowrap; padding: 0 6px; }
.page-nav .pg-mid:hover { color: var(--signal-deep); }
.page-nav svg { width: 18px; height: 18px; stroke: var(--signal-deep); fill: none; stroke-width: 2; flex-shrink: 0; }

@media (max-width: 880px) {
  .card-2 { grid-template-columns: 1fr; }
  .ladder { grid-template-columns: 1fr 1fr; }
  .trio { grid-template-columns: 1fr; }
  .feature-row { padding: 24px 22px; gap: 18px; }
  .page-nav { grid-template-columns: 1fr; }
  .page-nav .pg.next { justify-content: flex-start; text-align: left; }
  .page-nav .pg-mid { order: 3; text-align: center; }
  .svc-hero .ghost-num { opacity: 0.5; }
}
@media (max-width: 520px) {
  .ladder { grid-template-columns: 1fr; }
}