:root {
  --bg: #ffffff; --fg: #16181d; --muted: #5c6470; --line: #e3e6ea;
  --accent: #2456d6; --ok: #0f7b3f; --bad: #b3261e; --card: #f6f7f9;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #101318; --fg: #e8eaee; --muted: #98a0ac; --line: #2a2f38;
    --accent: #6d95ff; --ok: #4ccb84; --bad: #ff7a70; --card: #191d24;
  }
}
* { box-sizing: border-box }
body {
  margin: 0; background: var(--bg); color: var(--fg);
  font: 16px/1.6 system-ui, -apple-system, 'Segoe UI', sans-serif;
}
main { max-width: 860px; margin: 0 auto; padding: 2rem 1.25rem 4rem }
nav {
  display: flex; gap: 1.25rem; align-items: baseline;
  padding: 1rem 1.25rem; border-bottom: 1px solid var(--line);
  max-width: 860px; margin: 0 auto;
}
nav .brand { font-weight: 700; margin-right: auto; text-decoration: none; color: var(--fg) }
nav a { color: var(--muted); text-decoration: none }
nav a:hover { color: var(--accent) }
h1 { font-size: 1.7rem; line-height: 1.25 }
h2 { font-size: 1.2rem; margin-top: 2.2rem }
a { color: var(--accent) }
p.lead { font-size: 1.1rem; color: var(--muted) }
.card { background: var(--card); border: 1px solid var(--line); border-radius: 10px; padding: 1.25rem }
.drop {
  border: 2px dashed var(--line); border-radius: 12px; padding: 3rem 1rem;
  text-align: center; color: var(--muted); cursor: pointer; transition: border-color .15s;
}
.drop.hover, .drop:hover { border-color: var(--accent) }
.result { margin-top: 1.5rem }
.badge { display: inline-block; padding: .2rem .6rem; border-radius: 99px; font-size: .85rem; font-weight: 600 }
.badge.ok { background: color-mix(in srgb, var(--ok) 15%, transparent); color: var(--ok) }
.badge.bad { background: color-mix(in srgb, var(--bad) 15%, transparent); color: var(--bad) }
dl { display: grid; grid-template-columns: max-content 1fr; gap: .3rem 1.2rem; margin: 1rem 0 0 }
dt { color: var(--muted) }
dd { margin: 0; word-break: break-all }
table { border-collapse: collapse; width: 100%; font-size: .95rem }
th, td { text-align: left; padding: .45rem .6rem; border-bottom: 1px solid var(--line) }
code, pre { font-family: ui-monospace, 'SF Mono', Menlo, monospace; font-size: .9em }
pre { background: var(--card); border: 1px solid var(--line); border-radius: 8px; padding: 1rem; overflow-x: auto }
footer { color: var(--muted); font-size: .85rem; margin-top: 4rem; border-top: 1px solid var(--line); padding-top: 1rem }
form.card label { display: block; margin: 1rem 0 .3rem; color: var(--muted); font-size: .9rem }
form.card label:first-child { margin-top: 0 }
form.card input {
  width: 100%; padding: .65rem .8rem; border: 1px solid var(--line); border-radius: 8px;
  background: var(--bg); color: var(--fg); font: inherit;
}
form.card input:focus { outline: 2px solid var(--accent); border-color: transparent }
form.card button, .btn {
  display: inline-block; margin-top: 1.4rem; padding: .7rem 1.4rem; border: 0; border-radius: 8px;
  background: var(--accent); color: #fff; font: inherit; font-weight: 600;
  cursor: pointer; text-decoration: none;
}
form.card button:disabled { opacity: .6; cursor: default }
.btn.secondary { background: transparent; color: var(--accent); border: 1px solid var(--accent) }
.error { color: var(--bad); margin: 1rem 0 0 }
.note { color: var(--muted); font-size: .85rem }
.cta-row { display: flex; gap: .8rem; flex-wrap: wrap; margin: 1.5rem 0 }

/* ---------- landing ---------- */
.landing section { margin-top: 4.5rem }
.hero { margin-top: 2.5rem !important; text-align: left }
.eyebrow {
  color: var(--accent); font-weight: 600; font-size: .85rem;
  letter-spacing: .08em; text-transform: uppercase; margin-bottom: .4rem;
}
.hero h1 { font-size: clamp(2rem, 5.5vw, 3rem); line-height: 1.12; margin: .2rem 0 1rem }
.section-lead { color: var(--muted); max-width: 620px }
.btn.ghost { background: transparent; color: var(--muted); border: 1px solid var(--line) }
.btn.ghost:hover { color: var(--accent); border-color: var(--accent) }

.grid2 { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; margin-top: 1.2rem }
.grid3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1rem; margin-top: 1.2rem }
.card h3 { margin-top: 0; font-size: 1rem }

/* hero flow + layers diagram */
.hero-flow, .layers-diagram { width: 100%; height: auto; margin-top: 2.2rem }
.flow-node rect { fill: var(--card); stroke: var(--line); stroke-width: 1.5 }
.flow-node.ok rect { stroke: var(--ok) }
.flow-node.warn rect { stroke: var(--bad); stroke-dasharray: 5 4 }
.flow-node .icon { stroke: var(--accent); stroke-width: 2.5; stroke-linecap: round; stroke-linejoin: round }
.flow-node.ok .icon { stroke: var(--ok); stroke-width: 3.5 }
.flow-label { fill: var(--fg); font: 600 13px system-ui, sans-serif }
.flow-sub { fill: var(--muted); font: 400 11px system-ui, sans-serif }
.flow-arrow {
  fill: none; stroke: var(--muted); stroke-width: 1.5; stroke-dasharray: 6 5;
  marker-end: none;
}

/* steps */
.steps { display: grid; grid-template-columns: repeat(4, 1fr); gap: 1rem; margin-top: 1.4rem }
.step h3 { font-size: .95rem; margin: .8rem 0 .3rem }
.step p { font-size: .88rem; color: var(--muted); margin: 0 }
.step-icon {
  width: 56px; height: 56px; border-radius: 14px; background: var(--card);
  border: 1px solid var(--line); display: flex; align-items: center; justify-content: center;
}
.step-icon svg { width: 32px; height: 32px; stroke: var(--accent); stroke-width: 2.4;
  stroke-linecap: round; stroke-linejoin: round; fill: none }

/* payload layout diagram */
.pl-id { fill: color-mix(in srgb, var(--accent) 22%, transparent); stroke: var(--accent); stroke-width: 1.5 }
.pl-crc { fill: color-mix(in srgb, var(--ok) 22%, transparent); stroke: var(--ok); stroke-width: 1.5 }
.pl-rep { fill: var(--card); stroke: var(--line); stroke-width: 1.5 }

/* layer cards */
.dot { display: inline-block; width: 10px; height: 10px; border-radius: 50%;
  background: var(--accent); margin-right: .45rem }
.dot2 { background: var(--ok) }

/* KPI tiles */
.kpis { display: grid; grid-template-columns: repeat(4, 1fr); gap: 1rem; margin: 1.4rem 0 }
.kpi { background: var(--card); border: 1px solid var(--line); border-radius: 10px; padding: 1.1rem }
.kpi-value { font-size: 2rem; font-weight: 700; letter-spacing: -.02em }
.kpi-label { color: var(--muted); font-size: .82rem; margin-top: .3rem; line-height: 1.4 }

/* survival matrix */
.survival { margin-top: .4rem }
.matrix { list-style: none; padding: 0; margin: .8rem 0 0 }
.matrix li {
  display: flex; align-items: baseline; gap: .6rem; padding: .45rem 0;
  border-bottom: 1px solid var(--line); font-size: .95rem;
}
.matrix li:last-child { border-bottom: 0 }
.matrix .check { color: var(--ok); font-weight: 700 }
.matrix .val { margin-left: auto; font-variant-numeric: tabular-nums; font-weight: 600 }

/* timeline */
.timeline { display: grid; grid-template-columns: repeat(4, 1fr); gap: 1rem; margin: 1.4rem 0 }
.tl-item { border-top: 3px solid var(--line); padding-top: .8rem }
.tl-item.done { border-top-color: var(--muted) }
.tl-item.now { border-top-color: var(--accent) }
.tl-item p { font-size: .86rem; color: var(--muted); margin: .3rem 0 0 }
.tl-date { font-weight: 700; font-size: .9rem }
.tl-item.now .tl-date { color: var(--accent) }

.final-cta { text-align: center; padding: 2.5rem 0 0 }
.final-cta .cta-row { justify-content: center }
.final-cta .section-lead { margin-left: auto; margin-right: auto }

@media (max-width: 720px) {
  .grid2, .grid3, .steps, .kpis, .timeline { grid-template-columns: 1fr 1fr }
}
@media (max-width: 480px) {
  .grid2, .grid3, .steps { grid-template-columns: 1fr }
}