:root {
  color-scheme: light;
  --bg: #f5f7fa;
  --surface: #ffffff;
  --surface-muted: #eef4fa;
  --text: #18212b;
  --muted: #526170;
  --border: #d6dee8;
  --accent: #1f4f78;
  --accent-strong: #173a59;
  --accent-soft: #e4eef7;
  --code-bg: #0f172a;
  --code-text: #f8fafc;
  --code-border: #64748b;
  --inline-code-bg: #e8eef5;
  --inline-code-text: #102032;
  --shadow: rgba(31, 45, 61, 0.06);
  font-family: Arial, Helvetica, sans-serif;
}

* {
  box-sizing: border-box;
}

html {
  background: var(--bg);
}

body {
  margin: 0;
  color: var(--text);
  background: var(--bg);
  line-height: 1.6;
}

a {
  color: var(--accent);
}

a:hover,
a:focus {
  color: var(--accent-strong);
  text-decoration-thickness: 2px;
}

.site-header {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
}

.header-inner,
main,
.footer-inner {
  width: min(1040px, calc(100% - 32px));
  margin: 0 auto;
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  padding: 20px 0;
}

.brand {
  display: inline-flex;
  flex-direction: column;
  gap: 2px;
  color: var(--text);
  text-decoration: none;
}

.brand strong {
  font-size: 1.15rem;
  letter-spacing: 0.01em;
}

.brand span {
  color: var(--muted);
  font-size: 0.92rem;
}

nav {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  justify-content: flex-end;
}

nav a {
  color: var(--text);
  text-decoration: none;
  padding: 6px 9px;
  border-radius: 8px;
}

nav a:hover,
nav a:focus,
nav a.active,
nav a[aria-current="page"] {
  background: var(--accent-soft);
  color: var(--accent-strong);
}

main {
  padding: 36px 0 52px;
}

.hero,
.card,
.notice {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 14px;
  box-shadow: 0 10px 24px var(--shadow);
}

.hero {
  padding: 34px;
  margin-bottom: 24px;
}

.hero p {
  max-width: 850px;
  font-size: 1.08rem;
}

.eyebrow {
  margin: 0 0 8px;
  color: var(--accent-strong);
  font-weight: 700;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  font-size: 0.78rem;
}

h1,
h2,
h3 {
  line-height: 1.25;
  margin: 0 0 14px;
}

h1 {
  font-size: clamp(2rem, 4vw, 3rem);
}

h2 {
  font-size: 1.45rem;
}

h3 {
  font-size: 1.08rem;
}

p {
  margin: 0 0 14px;
}

p:last-child,
ul:last-child,
ol:last-child,
.flow:last-child,
.table-wrap:last-child {
  margin-bottom: 0;
}

.grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px;
}

.card,
.notice {
  padding: 24px;
  margin-bottom: 18px;
}

.notice {
  background: var(--surface-muted);
}

ul,
ol {
  margin: 0 0 12px 1.25rem;
  padding: 0;
}

li + li {
  margin-top: 6px;
}

.link-list a {
  font-weight: 700;
}

.flow {
  overflow-x: auto;
  margin: 16px 0;
  background: var(--code-bg);
  color: var(--code-text);
  border: 1px solid var(--code-border);
  padding: 18px;
  border-radius: 12px;
  font-size: 0.98rem;
  line-height: 1.65;
  font-weight: 700;
  letter-spacing: 0.01em;
}

.flow code {
  display: block;
  background: transparent;
  color: inherit;
  padding: 0;
  border-radius: 0;
  font-size: inherit;
  white-space: pre;
}

.table-wrap {
  overflow-x: auto;
  margin: 8px 0 4px;
}

table {
  width: 100%;
  border-collapse: collapse;
}

th,
td {
  text-align: left;
  vertical-align: top;
  border: 1px solid var(--border);
  padding: 10px 12px;
}

th {
  background: var(--surface-muted);
}

code {
  background: var(--inline-code-bg);
  color: var(--inline-code-text);
  padding: 2px 5px;
  border-radius: 5px;
  font-size: 0.95em;
}

pre code,
.flow code {
  background: transparent;
  color: inherit;
}

footer.site-footer {
  background: var(--surface);
  border-top: 1px solid var(--border);
  color: var(--muted);
}

.footer-inner {
  padding: 22px 0;
  font-size: 0.92rem;
}

.footer-links {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 8px;
}

@media (max-width: 760px) {
  .header-inner {
    align-items: flex-start;
    flex-direction: column;
  }

  nav {
    justify-content: flex-start;
  }

  .hero {
    padding: 24px;
  }

  .grid {
    grid-template-columns: 1fr;
  }
}

/* Operational specification diagrams */
.diagram {
  margin: 18px 0;
  padding: 18px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--surface-muted);
}

.diagram figcaption {
  margin-bottom: 14px;
  color: var(--accent-strong);
  font-weight: 700;
}

.process-diagram,
.activity-diagram {
  display: grid;
  gap: 10px;
  margin: 0;
  list-style: none;
}

.process-diagram > li,
.activity-diagram > li {
  position: relative;
  padding: 11px 14px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--surface);
  font-weight: 700;
}

.process-diagram > li:not(:last-child)::after,
.activity-diagram > li:not(:last-child)::after {
  content: "↓";
  position: absolute;
  left: 50%;
  bottom: -19px;
  color: var(--accent);
  transform: translateX(-50%);
}

.process-diagram span,
.case-diagram span,
.model-node span,
.contract-node span,
.class-diagram span {
  display: block;
  color: var(--muted);
  font-size: 0.92rem;
  font-weight: 400;
}

.decision { border-left: 4px solid var(--accent) !important; }
.decision-paths,
.activity-diagram .decision div {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
  margin-top: 10px;
  font-weight: 400;
}
.decision-paths > div,
.activity-diagram .decision div span {
  display: block;
  padding: 9px;
  border-radius: 6px;
  background: var(--accent-soft);
}
.error-path { color: #7c2d12; background: #fff7ed !important; }

.case-diagram,
.triple-diagram,
.class-diagram {
  display: grid;
  gap: 12px;
}
.case-diagram > div,
.model-node,
.contract-node,
.class-diagram > div {
  padding: 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--surface);
}
.case-milestones { display: flex; flex-wrap: wrap; gap: 8px; }
.case-milestones strong { width: 100%; }
.case-milestones span { padding: 4px 8px; border-radius: 999px; background: var(--accent-soft); }
.case-exit { border-left: 4px solid #a16207 !important; }

.model-row { display: grid; grid-template-columns: repeat(5, minmax(0, 1fr)); align-items: stretch; gap: 10px; }
.model-node { display: grid; align-content: start; gap: 6px; }
.model-node small { color: var(--muted); font-size: 0.82rem; }
.arrow { display: grid; align-content: center; color: var(--accent-strong); font-weight: 700; text-align: center; }
.diagram-notes { display: flex; flex-wrap: wrap; gap: 10px; color: var(--muted); font-size: 0.9rem; }
.diagram-notes span { flex: 1 1 260px; padding: 8px; border-left: 3px solid var(--accent); }

.diagram-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 18px; }
.diagram-grid .diagram { margin: 0; }
.component-diagram { display: flex; flex-wrap: wrap; align-items: center; justify-content: center; gap: 8px; }
.component-diagram div { padding: 8px; border: 1px solid var(--border); border-radius: 7px; background: var(--surface); text-align: center; font-size: 0.9rem; }
.component-diagram i { color: var(--accent); font-style: normal; font-weight: 700; }
.diagram-note { margin: 12px 0 0; color: var(--muted); font-size: 0.9rem; }
.sequence-diagram { padding: 12px; border-left: 4px solid var(--accent); background: var(--surface); }
.actors { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 12px; }
.actors span { padding: 3px 7px; border-radius: 999px; background: var(--accent-soft); font-size: 0.82rem; font-weight: 700; }
.sequence-diagram p:last-child { margin-bottom: 0; }
.state-diagram { display: grid; justify-items: center; gap: 5px; }
.state-diagram > div:not(.state-side) { width: min(100%, 220px); padding: 7px; border: 1px solid var(--border); border-radius: 999px; background: var(--surface); text-align: center; font-weight: 700; }
.state-diagram > span { color: var(--muted); font-size: 0.82rem; text-align: center; }
.state-side { width: 100%; margin-top: 8px; padding: 10px; border-radius: 8px; background: var(--accent-soft); font-size: 0.88rem; }
.class-diagram { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.class-diagram > div:first-child { grid-column: 1 / -1; border-top: 4px solid var(--accent); }

@media (max-width: 900px) {
  .model-row { grid-template-columns: 1fr; }
  .arrow { min-height: 20px; }
  .arrow::before { content: "↓"; }
  .diagram-grid { grid-template-columns: 1fr; }
}

@media (max-width: 560px) {
  .diagram { padding: 12px; }
  .decision-paths,
  .activity-diagram .decision div,
  .class-diagram { grid-template-columns: 1fr; }
  .class-diagram > div:first-child { grid-column: auto; }
}

.diagram .table-wrap {
  overflow: visible;
}

.diagram table {
  table-layout: fixed;
}