:root {
  color-scheme: dark;
  --color-background: #091012;
  --color-panel: #111b1e;
  --color-panel-strong: #182528;
  --color-line: #344649;
  --color-text: #f1f7f4;
  --color-muted: #a8bbb6;
  --color-accent: #6fe7be;
  --color-focus: #ffd166;
  --color-danger: #ff8a83;
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --radius-1: 0.25rem;
  --radius-2: 0.5rem;
  --content-width: 70rem;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  background: var(--color-background);
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--color-background);
  color: var(--color-text);
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 1rem;
  line-height: 1.6;
}

img {
  display: block;
  max-width: 100%;
  height: auto;
}

button,
select {
  min-width: 2.75rem;
  min-height: 2.75rem;
  border: 0.0625rem solid var(--color-muted);
  border-radius: var(--radius-1);
  background: var(--color-panel-strong);
  color: var(--color-text);
  font: inherit;
}

button {
  padding: var(--space-2) var(--space-4);
  cursor: pointer;
}

select {
  padding: var(--space-2) var(--space-8) var(--space-2) var(--space-3);
}

button:hover:not(:disabled),
select:hover {
  border-color: var(--color-accent);
}

button:disabled {
  border-style: dashed;
  background: transparent;
  color: var(--color-muted);
  cursor: not-allowed;
  opacity: 0.5;
}

a {
  color: var(--color-accent);
  text-underline-offset: var(--space-1);
}

a:hover {
  text-decoration-thickness: 0.125rem;
}

:focus-visible {
  outline: var(--space-1) solid var(--color-focus);
  outline-offset: var(--space-1);
}

.skip-link {
  position: fixed;
  z-index: 20;
  top: var(--space-4);
  left: var(--space-4);
  min-height: 2.75rem;
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-1);
  background: var(--color-focus);
  color: var(--color-background);
  font-weight: 800;
  transform: translateY(calc(-100% - var(--space-8)));
}

.skip-link:focus-visible {
  transform: translateY(0);
}

.site-header {
  position: sticky;
  z-index: 10;
  top: 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  min-height: 4rem;
  padding: var(--space-2) max(var(--space-4), calc((100% - var(--content-width)) / 2));
  border-bottom: 0.0625rem solid var(--color-line);
  background: var(--color-background);
}

.brand {
  display: inline-flex;
  align-items: center;
  min-height: 2.75rem;
  color: var(--color-text);
  font-weight: 800;
  letter-spacing: -0.025em;
  text-decoration: none;
  white-space: nowrap;
}

.site-header nav {
  display: flex;
  align-items: center;
  gap: var(--space-1);
}

.site-header nav a {
  display: inline-flex;
  align-items: center;
  min-height: 2.75rem;
  padding: var(--space-2);
  color: var(--color-muted);
  font-size: 0.875rem;
  font-weight: 700;
  text-decoration: none;
}

.site-header nav a:hover {
  color: var(--color-text);
  text-decoration: underline;
}

main > section {
  width: min(calc(100% - var(--space-8)), var(--content-width));
  margin-inline: auto;
  padding-block: var(--space-16);
  border-bottom: 0.0625rem solid var(--color-line);
  scroll-margin-top: var(--space-20);
}

main > section:last-child {
  border-bottom: 0;
}

h1,
h2,
h3,
p,
figure,
dl {
  margin-top: 0;
}

h1,
h2,
h3 {
  line-height: 1.12;
  text-wrap: balance;
}

h1 {
  max-width: 12ch;
  margin-bottom: var(--space-6);
  font-size: clamp(2.5rem, 7vw, 5.25rem);
  letter-spacing: -0.055em;
}

h2 {
  max-width: 18ch;
  margin-bottom: var(--space-8);
  font-size: clamp(2rem, 4vw, 3.25rem);
  letter-spacing: -0.04em;
}

h3 {
  margin-bottom: var(--space-3);
  font-size: 1.25rem;
}

p {
  max-width: 48rem;
  color: var(--color-muted);
}

.eyebrow,
.section-kicker {
  margin-bottom: var(--space-3);
  color: var(--color-accent);
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 0.16em;
}

.hero {
  padding-block: var(--space-20);
  background: linear-gradient(90deg, rgba(111, 231, 190, 0.08), transparent 62%);
}

.lead {
  max-width: 44rem;
  margin-bottom: var(--space-8);
  color: var(--color-text);
  font-size: clamp(1.125rem, 2vw, 1.375rem);
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-3);
  margin-bottom: var(--space-12);
}

.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 2.75rem;
  padding: var(--space-2) var(--space-5);
  border: 0.0625rem solid var(--color-accent);
  border-radius: var(--radius-1);
  font-weight: 800;
  text-decoration: none;
}

.button.primary {
  background: var(--color-accent);
  color: var(--color-background);
}

.button.primary:hover {
  background: var(--color-text);
  border-color: var(--color-text);
}

.safe-badge {
  display: inline-flex;
  align-items: center;
  min-height: 2.75rem;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-3);
  border: 0.0625rem solid var(--color-line);
  border-radius: var(--radius-1);
  color: var(--color-muted);
  font-weight: 700;
}

.safe-badge::before {
  content: "✓";
  color: var(--color-accent);
  font-weight: 900;
}

.metrics {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: var(--space-4);
  margin-bottom: 0;
}

.metrics div {
  padding-top: var(--space-4);
  border-top: 0.25rem solid var(--color-accent);
}

.metrics dt,
.run-stats dt {
  color: var(--color-muted);
  font-size: 0.875rem;
}

.metrics dd,
.run-stats dd {
  margin-left: 0;
  color: var(--color-text);
  font-weight: 800;
}

.metrics dd {
  margin-top: var(--space-2);
  font-size: clamp(1.25rem, 3vw, 2rem);
}

.proof-grid,
.boundary-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: var(--space-8);
  align-items: start;
}

.proof-grid > *,
.boundary-grid > *,
.card-grid > * {
  min-width: 0;
}

.run-stats {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: var(--space-1);
  margin-bottom: 0;
  border: 0.0625rem solid var(--color-line);
  background: var(--color-panel);
}

.run-stats div {
  min-width: 0;
  padding: var(--space-5);
  border: 0.0625rem solid var(--color-line);
}

.run-stats dd {
  margin-top: var(--space-2);
  font-size: 1.5rem;
}

.proof-grid figure {
  margin-bottom: 0;
}

.proof-grid img {
  width: 100%;
  max-height: 32rem;
  aspect-ratio: 1 / 1;
  border: 0.0625rem solid var(--color-line);
  border-radius: var(--radius-2);
  object-fit: contain;
}

.proof-grid figcaption {
  margin-top: var(--space-2);
  color: var(--color-muted);
  font-size: 0.875rem;
}

.replay-toolbar {
  display: grid;
  grid-template-columns: auto minmax(10rem, 14rem) 1fr;
  align-items: center;
  gap: var(--space-3);
  margin-block: var(--space-8) var(--space-4);
}

.replay-toolbar label {
  font-weight: 800;
}

#run-summary {
  color: var(--color-muted);
  text-align: right;
}

.message-card {
  border: 0.0625rem solid var(--color-line);
  border-radius: var(--radius-2);
  background: var(--color-panel);
}

.message-card > header,
.message-card > footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  padding: var(--space-4);
  background: var(--color-panel-strong);
}

.message-card > header {
  border-bottom: 0.0625rem solid var(--color-line);
}

.message-card > footer {
  border-top: 0.0625rem solid var(--color-line);
}

.message-card > header span {
  font-weight: 800;
}

#segment-label {
  color: var(--color-accent);
}

.message-output {
  min-height: 16rem;
  max-height: 34rem;
  padding: var(--space-5);
  overflow: auto;
  color: var(--color-text);
  line-height: 1.75;
  overflow-wrap: anywhere;
  white-space: pre-wrap;
}

.message-output p {
  color: inherit;
}

.message-output a {
  word-break: break-word;
}

#segment-tabs {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: var(--space-2);
}

#segment-tabs button {
  padding-inline: var(--space-3);
}

#segment-tabs button[aria-pressed="true"] {
  border-color: var(--color-accent);
  background: var(--color-accent);
  color: var(--color-background);
  font-weight: 900;
  text-decoration: underline;
  text-decoration-thickness: 0.125rem;
  text-underline-offset: var(--space-1);
}

.status {
  margin-top: var(--space-3);
  color: var(--color-muted);
  font-size: 0.875rem;
}

.workflow {
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: var(--space-4);
  margin: 0;
  padding: 0;
  counter-reset: workflow;
  list-style: none;
}

.workflow li {
  min-width: 0;
  padding-top: var(--space-4);
  border-top: 0.25rem solid var(--color-line);
  counter-increment: workflow;
}

.workflow li::before {
  display: block;
  margin-bottom: var(--space-4);
  color: var(--color-accent);
  content: "0" counter(workflow);
  font-size: 0.75rem;
  font-weight: 900;
  letter-spacing: 0.12em;
}

.workflow strong,
.workflow span {
  display: block;
}

.workflow span {
  margin-top: var(--space-2);
  color: var(--color-muted);
  font-size: 0.875rem;
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: var(--space-6);
  counter-reset: tool;
}

.card-grid article {
  padding-top: var(--space-4);
  border-top: 0.25rem solid var(--color-accent);
  counter-increment: tool;
}

.card-grid article::before {
  color: var(--color-muted);
  content: "0" counter(tool);
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 0.12em;
}

.card-grid h3 {
  margin-top: var(--space-4);
}

.card-grid p {
  margin-bottom: 0;
}

.boundary-grid article {
  padding: var(--space-6);
  border-left: 0.25rem solid var(--color-accent);
  background: var(--color-panel);
}

.boundary-grid .cannot {
  border-left-color: var(--color-danger);
}

.boundary-grid ul {
  margin: 0;
  padding-left: var(--space-5);
}

.boundary-grid li + li {
  margin-top: var(--space-2);
}

.boundary-grid .can li::marker {
  color: var(--color-accent);
}

.boundary-grid .cannot li::marker {
  color: var(--color-danger);
}

.site-footer {
  padding: var(--space-8) max(var(--space-4), calc((100% - var(--content-width)) / 2));
  border-top: 0.0625rem solid var(--color-line);
  background: var(--color-panel);
}

.site-footer p {
  margin-bottom: 0;
  font-size: 0.875rem;
}

@media (max-width: 64rem) {
  .card-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 760px) {
  .site-header {
    min-height: 3.5rem;
    padding-inline: var(--space-4);
  }

  .site-header nav {
    display: none;
  }

  main > section {
    padding-block: var(--space-12);
  }

  .hero {
    padding-block: var(--space-16);
  }

  .hero-actions {
    align-items: stretch;
    flex-direction: column;
  }

  .button,
  .safe-badge {
    justify-content: center;
    width: 100%;
  }

  .metrics,
  .proof-grid,
  .boundary-grid,
  .workflow,
  .card-grid {
    grid-template-columns: minmax(0, 1fr);
  }

  .run-stats {
    grid-template-columns: minmax(0, 1fr);
  }

  .replay-toolbar {
    grid-template-columns: minmax(0, 1fr);
  }

  #run-summary {
    text-align: left;
  }

  .message-card > footer {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  #previous-segment {
    grid-column: 1;
    grid-row: 1;
  }

  #next-segment {
    grid-column: 2;
    grid-row: 1;
  }

  #segment-tabs {
    grid-column: 1 / -1;
    grid-row: 2;
  }

  .message-output {
    min-height: 14rem;
    max-height: 28rem;
    padding: var(--space-4);
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
}