/* version: 1.0.0 | build: 2026-09-17 | update: 2026-09-17 */
/* ==========================================================================
   MSR STANDARD — OFFICIAL PROTOCOL DESIGN SYSTEM
   Theme: Technical, Minimal, Timeless, Vendor-Neutral, Engineering-Focused
   Reference Standards: ietf.org, schema.org, openapi.dev, python.org, kubernetes.io
   ========================================================================== */

:root {
  --color-primary: #0f172a;
  /* Slate 900 - Headings & Primary Elements */
  --color-primary-light: #1e293b;
  /* Slate 800 */
  --color-secondary: #2563eb;
  /* Blue 600 - Standard Engineering Action */
  --color-secondary-hover: #1d4ed8;
  --color-accent: #06b6d4;
  /* Cyan 500 - Protocol Highlighting */
  --color-success: #10b981;
  /* Emerald 500 - Validated / Stable */
  --color-warning: #f59e0b;
  /* Amber 500 */
  --color-danger: #ef4444;
  /* Red 500 */

  --bg-body: #ffffff;
  --bg-surface: #f8fafc;
  /* Slate 50 */
  --bg-subtle: #f1f5f9;
  /* Slate 100 */
  --bg-code: #0f172a;

  --border-color: #e2e8f0;
  /* Slate 200 */
  --border-subtle: #cbd5e1;
  /* Slate 300 */

  --text-primary: #0f172a;
  --text-muted: #475569;
  /* Slate 600 */
  --text-subtle: #64748b;
  /* Slate 500 */

  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, "SF Mono", "Cascadia Code", "JetBrains Mono", Consolas, "Liberation Mono", Menlo, monospace;

  --max-width: 1200px;
  --header-height: 64px;
  --radius-sm: 4px;
  --radius-md: 6px;
  --radius-lg: 8px;
  --shadow-subtle: 0 1px 3px 0 rgba(0, 0, 0, 0.05), 0 1px 2px -1px rgba(0, 0, 0, 0.05);
}

/* Reset & Base */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-height) + 24px);
  -webkit-font-smoothing: antialiased;
}

body {
  font-family: var(--font-sans);
  color: var(--text-primary);
  background-color: var(--bg-body);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

a {
  color: var(--color-secondary);
  text-decoration: none;
  transition: color 0.15s ease;
}

a:hover {
  color: var(--color-secondary-hover);
  text-decoration: underline;
}

code,
kbd,
samp,
pre {
  font-family: var(--font-mono);
  font-size: 0.9em;
}

code {
  background: var(--bg-subtle);
  color: var(--color-primary);
  padding: 0.15em 0.4em;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
}

pre code {
  background: transparent;
  padding: 0;
  border: none;
  color: #e2e8f0;
}

h1,
h2,
h3,
h4,
h5,
h6 {
  color: var(--color-primary);
  font-weight: 700;
  line-height: 1.25;
}

h1 {
  font-size: 2.25rem;
  letter-spacing: -0.025em;
}

h2 {
  font-size: 1.75rem;
  letter-spacing: -0.02em;
  margin-top: 2.5rem;
  margin-bottom: 1rem;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 0.5rem;
}

h3 {
  font-size: 1.35rem;
  margin-top: 1.75rem;
  margin-bottom: 0.75rem;
}

h4 {
  font-size: 1.1rem;
  margin-top: 1.25rem;
  margin-bottom: 0.5rem;
}

p {
  margin-bottom: 1rem;
  color: var(--text-muted);
}

strong {
  color: var(--text-primary);
  font-weight: 600;
}

ul,
ol {
  margin-bottom: 1.25rem;
  padding-left: 1.75rem;
  color: var(--text-muted);
}

li {
  margin-bottom: 0.4rem;
}

/* Header & Navigation */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: #ffffff;
  border-bottom: 1px solid var(--border-color);
  box-shadow: var(--shadow-subtle);
}

.header-container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.5rem;
  height: var(--header-height);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.5rem;
}

.brand-link {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  text-decoration: none;
}

.brand-logo {
  height: 38px;
  width: auto;
  display: block;
}

.nav-menu {
  display: flex;
  align-items: center;
  gap: 0.25rem;
  list-style: none;
  padding: 0;
  margin: 0;
}

.nav-link {
  padding: 0.45rem 0.65rem;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-muted);
  border-radius: var(--radius-sm);
  transition: all 0.15s ease;
  white-space: nowrap;
}

.nav-link:hover {
  color: var(--color-primary);
  background-color: var(--bg-surface);
  text-decoration: none;
}

.nav-link.active {
  color: var(--color-secondary);
  font-weight: 600;
  background-color: #eff6ff;
}

.nav-meta-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.25rem 0.6rem;
  background-color: #ecfdf5;
  border: 1px solid #a7f3d0;
  color: #065f46;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 600;
  border-radius: 9999px;
  white-space: nowrap;
}

.nav-meta-badge .dot {
  width: 6px;
  height: 6px;
  background-color: var(--color-success);
  border-radius: 50%;
}

.mobile-menu-toggle {
  display: none;
  background: none;
  border: 1px solid var(--border-color);
  padding: 0.4rem 0.6rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
}

/* Layout Containers */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 2.5rem 1.5rem;
  width: 100%;
}

.doc-layout {
  display: grid;
  grid-template-columns: 240px 1fr;
  gap: 3rem;
  align-items: start;
}

.doc-sidebar {
  position: sticky;
  top: calc(var(--header-height) + 2rem);
  max-height: calc(100vh - var(--header-height) - 4rem);
  overflow-y: auto;
  padding-right: 1rem;
  font-size: 0.875rem;
}

.sidebar-heading {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-subtle);
  margin-bottom: 0.75rem;
}

.sidebar-nav {
  list-style: none;
  padding: 0;
  margin: 0 0 1.5rem 0;
}

.sidebar-nav li {
  margin-bottom: 0.25rem;
}

.sidebar-nav a {
  display: block;
  padding: 0.35rem 0.5rem;
  color: var(--text-muted);
  border-radius: var(--radius-sm);
  text-decoration: none;
}

.sidebar-nav a:hover {
  color: var(--color-primary);
  background-color: var(--bg-surface);
}

.sidebar-nav a.active {
  color: var(--color-secondary);
  font-weight: 600;
  background-color: #eff6ff;
}

/* Technical Hero */
.hero {
  background: linear-gradient(180deg, #ffffff 0%, #f8fafc 100%);
  border-bottom: 1px solid var(--border-color);
  padding: 4.5rem 1.5rem 4rem 1.5rem;
}

.hero-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: 3.5rem;
  align-items: center;
}

.hero-tag {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--color-secondary);
  background-color: #eff6ff;
  border: 1px solid #bfdbfe;
  padding: 0.25rem 0.75rem;
  border-radius: var(--radius-sm);
  margin-bottom: 1.25rem;
}

.hero-title {
  font-size: 3rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1.15;
  color: var(--color-primary);
  margin-bottom: 1rem;
}

.hero-subtitle-lg {
  font-size: 1.25rem;
  font-weight: 500;
  color: var(--color-primary-light);
  margin-bottom: 1rem;
  line-height: 1.4;
}

.hero-desc {
  font-size: 1.0625rem;
  color: var(--text-muted);
  line-height: 1.6;
  margin-bottom: 2rem;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.875rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.65rem 1.25rem;
  font-size: 0.9375rem;
  font-weight: 600;
  border-radius: var(--radius-sm);
  text-decoration: none;
  cursor: pointer;
  transition: all 0.15s ease;
  border: 1px solid transparent;
}

.btn-primary {
  background-color: var(--color-primary);
  color: #ffffff;
}

.btn-primary:hover {
  background-color: var(--color-primary-light);
  color: #ffffff;
  text-decoration: none;
}

.btn-secondary {
  background-color: #ffffff;
  border-color: var(--border-subtle);
  color: var(--color-primary);
}

.btn-secondary:hover {
  border-color: var(--color-primary);
  background-color: var(--bg-surface);
  text-decoration: none;
}

.btn-blue {
  background-color: var(--color-secondary);
  color: #ffffff;
}

.btn-blue:hover {
  background-color: var(--color-secondary-hover);
  color: #ffffff;
  text-decoration: none;
}

/* Code Snippet Box in Hero */
.hero-code-box {
  background: var(--bg-code);
  border-radius: var(--radius-lg);
  border: 1px solid #1e293b;
  box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.2), 0 8px 10px -6px rgba(0, 0, 0, 0.2);
  overflow: hidden;
}

.code-header {
  background: #1e293b;
  padding: 0.6rem 1rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-bottom: 1px solid #334155;
}

.code-title {
  color: #94a3b8;
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.code-title .circle {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--color-accent);
}

.copy-btn {
  background: transparent;
  border: 1px solid #475569;
  color: #cbd5e1;
  font-size: 0.75rem;
  padding: 0.2rem 0.5rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
}

.copy-btn:hover {
  background: #334155;
  color: #ffffff;
}

.code-content {
  padding: 1rem;
  overflow-x: auto;
  font-size: 0.8125rem;
  line-height: 1.5;
  color: #e2e8f0;
}

/* Protocol Pipeline Architecture Diagram */
.pipeline-section {
  padding: 3.5rem 0;
  border-bottom: 1px solid var(--border-color);
  background-color: #ffffff;
}

.pipeline-diagram {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 1rem;
  margin-top: 2rem;
  padding: 1.5rem;
  background-color: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
}

.pipeline-node {
  flex: 1;
  min-width: 140px;
  background-color: #ffffff;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.25rem 1rem;
  text-align: center;
  box-shadow: var(--shadow-subtle);
  position: relative;
}

.pipeline-node.active-root {
  border-color: var(--color-secondary);
  background-color: #f0f7ff;
}

.pipeline-node .node-badge {
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  text-transform: uppercase;
  font-weight: 700;
  color: var(--color-secondary);
  letter-spacing: 0.05em;
  margin-bottom: 0.25rem;
}

.pipeline-node .node-title {
  font-weight: 700;
  font-size: 0.9375rem;
  color: var(--color-primary);
  margin-bottom: 0.25rem;
}

.pipeline-node .node-desc {
  font-size: 0.75rem;
  color: var(--text-subtle);
  line-height: 1.35;
  margin: 0;
}

.pipeline-arrow {
  color: var(--text-subtle);
  font-weight: bold;
  font-size: 1.25rem;
  user-select: none;
}

/* Feature Grid & Problem Solving */
.grid-2 {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.5rem;
  margin: 2rem 0;
}

.grid-3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
  margin: 2rem 0;
}

.card {
  background-color: #ffffff;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.card:hover {
  border-color: var(--border-subtle);
  box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.05);
}

.card-icon {
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-sm);
  background-color: #eff6ff;
  color: var(--color-secondary);
  margin-bottom: 1rem;
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: 0.875rem;
}

.card-title {
  font-size: 1.125rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
  color: var(--color-primary);
}

.card-text {
  font-size: 0.875rem;
  color: var(--text-muted);
  line-height: 1.5;
  margin: 0;
}

/* Architecture Block Deep Dive */
.arch-block {
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  margin-bottom: 2rem;
  background: #ffffff;
  overflow: hidden;
}

.arch-block-header {
  background-color: var(--bg-surface);
  border-bottom: 1px solid var(--border-color);
  padding: 1rem 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.arch-block-title {
  font-family: var(--font-mono);
  font-size: 1.125rem;
  font-weight: 700;
  color: var(--color-primary);
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.arch-block-badge {
  font-size: 0.75rem;
  font-weight: 600;
  padding: 0.2rem 0.5rem;
  border-radius: var(--radius-sm);
  text-transform: uppercase;
}

.badge-required {
  background-color: #fef2f2;
  border: 1px solid #fecaca;
  color: #991b1b;
}

.badge-optional {
  background-color: #f8fafc;
  border: 1px solid #e2e8f0;
  color: #475569;
}

.badge-stable {
  background-color: #ecfdf5;
  border: 1px solid #a7f3d0;
  color: #065f46;
}

.arch-block-body {
  padding: 1.5rem;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 2rem;
}

/* Technical Tables */
.table-wrapper {
  overflow-x: auto;
  margin: 1.5rem 0;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
}

.tech-table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
  font-size: 0.875rem;
}

.tech-table th {
  background-color: var(--bg-surface);
  color: var(--color-primary);
  font-weight: 600;
  padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--border-color);
  white-space: nowrap;
}

.tech-table td {
  padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--border-color);
  color: var(--text-muted);
  vertical-align: top;
}

.tech-table tr:last-child td {
  border-bottom: none;
}

.tech-table tr:hover td {
  background-color: #fafbfc;
}

/* In-Page Notice & Alerts */
.callout {
  padding: 1.25rem;
  border-left: 4px solid var(--color-secondary);
  background-color: #f8fafc;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  margin: 1.5rem 0;
  font-size: 0.9375rem;
}

.callout-title {
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: 0.25rem;
}

.callout-success {
  border-left-color: var(--color-success);
  background-color: #f0fdf4;
}

.callout-warning {
  border-left-color: var(--color-warning);
  background-color: #fffbeb;
}

/* Validator Component */
.validator-container {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
  margin-top: 1.5rem;
  align-items: stretch;
}

.validator-editor,
.validator-results {
  background-color: #ffffff;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  display: flex;
  flex-direction: column;
}

.validator-toolbar {
  background-color: var(--bg-surface);
  border-bottom: 1px solid var(--border-color);
  padding: 0.75rem 1rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.validator-textarea {
  width: 100%;
  height: 480px;
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  padding: 1rem;
  border: none;
  resize: vertical;
  color: var(--color-primary);
  background-color: #ffffff;
  outline: none;
  line-height: 1.5;
}

.validator-textarea:focus {
  background-color: #fafbfc;
}

.results-content {
  padding: 1.25rem;
  overflow-y: auto;
  max-height: 520px;
  font-size: 0.875rem;
}

.result-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.35rem 0.75rem;
  border-radius: var(--radius-sm);
  font-weight: 700;
  font-family: var(--font-mono);
  font-size: 0.875rem;
}

.result-badge.pass {
  background-color: #ecfdf5;
  color: #065f46;
  border: 1px solid #a7f3d0;
}

.result-badge.fail {
  background-color: #fef2f2;
  color: #991b1b;
  border: 1px solid #fecaca;
}

.validation-checklist {
  list-style: none;
  padding: 0;
  margin: 1rem 0;
}

.validation-checklist li {
  padding: 0.5rem 0;
  border-bottom: 1px dashed var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 0.8125rem;
}

.check-status {
  font-family: var(--font-mono);
  font-weight: 700;
}

/* Tabs Component */
.tab-container {
  margin: 1.5rem 0;
}

.tab-headers {
  display: flex;
  gap: 0.5rem;
  border-bottom: 1px solid var(--border-color);
  overflow-x: auto;
}

.tab-btn {
  background: none;
  border: none;
  padding: 0.6rem 1rem;
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-muted);
  cursor: pointer;
  border-bottom: 2px solid transparent;
  white-space: nowrap;
}

.tab-btn:hover {
  color: var(--color-primary);
}

.tab-btn.active {
  color: var(--color-secondary);
  border-bottom-color: var(--color-secondary);
}

.tab-content {
  display: none;
  padding-top: 1rem;
}

.tab-content.active {
  display: block;
}

/* Footer */
.site-footer {
  margin-top: auto;
  background-color: #ffffff;
  border-top: 1px solid var(--border-color);
  padding: 3.5rem 1.5rem 2.5rem 1.5rem;
  font-size: 0.875rem;
}

.footer-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  display: grid;
  grid-template-columns: 2fr repeat(3, 1fr);
  gap: 3rem;
  margin-bottom: 2.5rem;
}

.footer-brand p {
  font-size: 0.875rem;
  margin-top: 0.75rem;
  max-width: 320px;
}

.footer-col h5 {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-subtle);
  margin-bottom: 1rem;
}

.footer-links {
  list-style: none;
  padding: 0;
  margin: 0;
}

.footer-links li {
  margin-bottom: 0.5rem;
}

.footer-links a {
  color: var(--text-muted);
}

.footer-links a:hover {
  color: var(--color-primary);
}

.footer-bottom {
  max-width: var(--max-width);
  margin: 0 auto;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 1rem;
  color: var(--text-subtle);
  font-size: 0.8125rem;
}

/* Responsive */
@media (max-width: 960px) {
  .hero-inner {
    grid-template-columns: 1fr;
    gap: 2.5rem;
  }

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

  .doc-sidebar {
    position: static;
    max-height: none;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 1.5rem;
    margin-bottom: 2rem;
  }

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

  .arch-block-body {
    grid-template-columns: 1fr;
  }

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

  .grid-2,
  .grid-3 {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 768px) {
  .nav-menu {
    display: none;
    position: absolute;
    top: var(--header-height);
    left: 0;
    right: 0;
    background-color: #ffffff;
    border-bottom: 1px solid var(--border-color);
    flex-direction: column;
    padding: 1rem;
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
  }

  .nav-menu.open {
    display: flex;
  }

  .mobile-menu-toggle {
    display: block;
  }

  .hero-title {
    font-size: 2.25rem;
  }

  .footer-inner {
    grid-template-columns: 1fr;
    gap: 2rem;
  }
}