:root {
  --bg: #f6f7f9;
  --surface: #ffffff;
  --ink: #1a2233;
  --muted: #5b6577;
  --accent: #0f4c81;
  --accent-soft: #e8f0f8;
  --border: #dfe4ea;
  --radius: 10px;
  --mono: ui-monospace, "Cascadia Code", Consolas, monospace;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.65;
}

.wrap { max-width: 1080px; margin: 0 auto; padding: 0 24px; }

/* Header */
header {
  background: linear-gradient(135deg, #0d2b45 0%, #0f4c81 100%);
  color: #fff;
  position: sticky;
  top: 0;
  z-index: 20;
  box-shadow: 0 2px 12px rgba(13, 43, 69, .25);
}
.brand { display: flex; align-items: center; gap: 14px; padding: 18px 0 10px; }
.logo {
  display: inline-flex; align-items: center; justify-content: center;
  width: 44px; height: 44px; border-radius: 12px;
  background: rgba(255,255,255,.12); border: 1px solid rgba(255,255,255,.25);
  font-weight: 800; letter-spacing: .5px;
}
.brand h1 { margin: 0; font-size: 19px; font-weight: 700; }
.brand p { margin: 2px 0 0; font-size: 12.5px; opacity: .75; }

.tabs { display: flex; gap: 4px; overflow-x: auto; padding-bottom: 0; }
.tab {
  appearance: none; border: none; cursor: pointer;
  background: transparent; color: rgba(255,255,255,.75);
  font-size: 13.5px; font-weight: 600; white-space: nowrap;
  padding: 10px 14px; border-radius: 8px 8px 0 0;
  border-bottom: 3px solid transparent;
  transition: color .15s, border-color .15s, background .15s;
}
.tab:hover { color: #fff; background: rgba(255,255,255,.08); }
.tab.active { color: #fff; border-bottom-color: #7fc4ff; background: rgba(255,255,255,.10); }

/* Content */
main { padding: 32px 24px 64px; }
section.doc { display: none; background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 36px 44px; box-shadow: 0 1px 4px rgba(26,34,51,.05); }
section.doc.active { display: block; animation: fade .2s ease; }
@keyframes fade { from { opacity: 0; transform: translateY(4px);} to { opacity: 1; transform: none;} }

section.doc h1 { font-size: 26px; margin: 0 0 8px; color: var(--accent); border-bottom: 2px solid var(--accent-soft); padding-bottom: 12px; }
section.doc h2 { font-size: 20px; margin-top: 40px; color: #12395e; }
section.doc h3 { font-size: 16.5px; margin-top: 28px; }
section.doc h4 { font-size: 14.5px; margin-top: 22px; }

section.doc blockquote {
  margin: 16px 0; padding: 10px 18px;
  background: var(--accent-soft); border-left: 4px solid var(--accent);
  border-radius: 0 8px 8px 0; color: var(--muted); font-size: 14px;
}
section.doc blockquote p { margin: 4px 0; }

section.doc a { color: var(--accent); }
section.doc code {
  font-family: var(--mono); font-size: .88em;
  background: #eef1f5; border: 1px solid #e2e6ec;
  padding: 1px 5px; border-radius: 5px;
}
section.doc pre {
  background: #0d1b2a; color: #dce6f2; border-radius: 8px;
  padding: 18px 20px; overflow-x: auto; font-size: 13px; line-height: 1.55;
}
section.doc pre code { background: none; border: none; padding: 0; color: inherit; }

/* Tables */
section.doc table { border-collapse: collapse; width: 100%; margin: 18px 0; font-size: 13.5px; }
section.doc th {
  background: var(--accent-soft); color: #12395e; text-align: left;
  padding: 9px 12px; border: 1px solid var(--border); font-weight: 700;
}
section.doc td { padding: 8px 12px; border: 1px solid var(--border); vertical-align: top; }
section.doc tr:nth-child(even) td { background: #fafbfc; }

/* Diagrams */
figure.diagram {
  margin: 24px 0; padding: 20px; text-align: center;
  background: #fff; border: 1px solid var(--border); border-radius: 8px;
  overflow-x: auto;
}
figure.diagram img { max-width: 100%; height: auto; }

/* Checkboxes in lists */
section.doc input[type="checkbox"] { margin-right: 6px; }

footer { border-top: 1px solid var(--border); padding: 18px 0; color: var(--muted); font-size: 12.5px; }

/* Login gate */
body.locked header, body.locked main, body.locked footer { display: none; }
#login {
  min-height: 100vh; display: flex; align-items: center; justify-content: center;
  background: linear-gradient(135deg, #0d2b45 0%, #0f4c81 100%);
}
body:not(.locked) #login { display: none; }
#login form {
  background: var(--surface); border-radius: 14px; padding: 40px 44px;
  width: 340px; text-align: center; box-shadow: 0 12px 40px rgba(0,0,0,.35);
}
#login .logo.big {
  width: 56px; height: 56px; margin: 0 auto 14px; font-size: 20px;
  display: flex; align-items: center; justify-content: center; border-radius: 14px;
  background: var(--accent-soft); border: 1px solid var(--border);
  color: var(--accent); font-weight: 800;
}
#login h2 { margin: 0 0 4px; font-size: 19px; color: var(--ink); }
#login p { margin: 0 0 22px; font-size: 13px; color: var(--muted); }
#login input {
  display: block; width: 100%; margin-bottom: 12px;
  padding: 10px 14px; font-size: 14px;
  border: 1px solid var(--border); border-radius: 8px; outline: none;
}
#login input:focus { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }
#login button {
  width: 100%; padding: 11px; border: none; border-radius: 8px; cursor: pointer;
  background: var(--accent); color: #fff; font-size: 14.5px; font-weight: 700;
}
#login button:hover { background: #0d3f6b; }
#login-error { margin-top: 12px; color: #c0392b; font-size: 13px; }

@media (max-width: 720px) {
  section.doc { padding: 24px 18px; }
  .brand h1 { font-size: 16px; }
}