/* ==========================================================================
   Bifrost — one-page site

   The palette is lifted from assets/bifrost.svg so the page and the app icon
   agree: a deep slate field with one muted dawn arc running cool blue → sage →
   sand → clay. That arc is the only saturated thing here and it appears exactly
   twice, in the hero and on the bridge rule above the demo. Everything else is
   ink on hairlines.
   ========================================================================== */

:root {
  /* Field */
  --field:      #0b121d;
  --field-2:    #0e1725;
  --panel:      #101a2c;
  --panel-hi:   #172235;
  --hairline:   #223148;
  --hairline-2: #2d3f59;

  /* Ink */
  --ink:        #e8eef5;
  --ink-2:      #94a4ba;
  --ink-3:      #64758d;

  /* The arc, straight off the icon */
  --arc-1:      #8fbfd0;
  --arc-2:      #d5dec6;
  --arc-3:      #e1d1ae;
  --arc-4:      #b58e82;
  --arc: linear-gradient(90deg,
          var(--arc-1) 0%, var(--arc-2) 44%, var(--arc-3) 72%, var(--arc-4) 100%);

  /* Type. DM Sans for anything a person reads: near-circular bowls and soft
     joins, to offset a page that is otherwise all terminal output. Geist Mono
     for anything the machine said. */
  --display: "DM Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --body:    "DM Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --mono:    "Geist Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;

  /* Measure and rhythm */
  --measure: 62ch;
  --gutter:  clamp(1.25rem, 4vw, 3rem);
  --bay:     clamp(3.5rem, 7vw, 6rem);
}

/* --------------------------------------------------------------------------
   Base
   -------------------------------------------------------------------------- */

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

html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--field);
  color: var(--ink);
  font-family: var(--body);
  font-size: 1rem;
  line-height: 1.62;
  font-synthesis: none;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3 {
  font-family: var(--display);
  font-weight: 600;
  line-height: 1.08;
  letter-spacing: -0.022em;
  margin: 0;
  text-wrap: balance;
}

h1 { font-size: clamp(2.25rem, 4.8vw, 3.4rem); }
h2 { font-size: clamp(1.7rem, 3.2vw, 2.5rem); }
h3 { font-size: 1.0625rem; letter-spacing: -0.01em; }

p { margin: 0 0 1rem; }

a { color: var(--arc-1); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 3px; }

code, pre, kbd { font-family: var(--mono); }

code {
  font-size: 0.875em;
  color: var(--arc-2);
  background: rgba(143, 191, 208, 0.09);
  padding: 0.1em 0.34em;
  border-radius: 3px;
  /* Flags and paths must not break mid-token: "--config" split across two
     lines reads as two different flags. */
  white-space: nowrap;
}

:focus-visible {
  outline: 2px solid var(--arc-1);
  outline-offset: 3px;
  border-radius: 2px;
}

.wrap {
  width: min(1120px, 100%);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.muted  { color: var(--ink-2); font-size: 0.9375rem; }
.dim    { color: var(--ink-3); }

.vh {
  position: absolute;
  width: 1px; height: 1px;
  margin: -1px; padding: 0;
  overflow: hidden;
  clip-path: inset(50%);
  white-space: nowrap;
}

.skip {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--panel-hi);
  color: var(--ink);
  padding: 0.75rem 1rem;
  z-index: 20;
}
.skip:focus { left: 0; }

/* --------------------------------------------------------------------------
   Top bar
   -------------------------------------------------------------------------- */

.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  background: color-mix(in srgb, var(--field) 88%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--hairline);
}

.topbar-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.5rem;
  min-height: 60px;
}

.brand { display: flex; align-items: center; gap: 0.6rem; color: var(--ink); }
.brand:hover { text-decoration: none; }
.brand-mark { width: 26px; height: 26px; display: block; }

.brand-word {
  font-family: var(--display);
  font-weight: 600;
  font-size: 1.0625rem;
  letter-spacing: -0.01em;
}

.topnav { display: flex; align-items: center; gap: 1.5rem; }

.topnav a {
  color: var(--ink-2);
  font-size: 0.875rem;
}
.topnav a:hover { color: var(--ink); text-decoration: none; }

.topnav-cta {
  color: var(--ink) !important;
  border: 1px solid var(--hairline-2);
  border-radius: 999px;
  padding: 0.3rem 0.85rem;
}
.topnav-cta:hover { border-color: var(--arc-1); }

/* --------------------------------------------------------------------------
   Hero
   -------------------------------------------------------------------------- */

.hero { padding-block: clamp(2.5rem, 5vw, 4rem) clamp(3rem, 6vw, 4.75rem); }

/* The letter. A message sitting on the page, not a card holding marketing. */
.letter {
  width: min(880px, 100%);
  margin-inline: auto;
  background: linear-gradient(180deg, var(--panel-hi), var(--panel));
  border: 1px solid var(--hairline-2);
  border-radius: 10px;
  overflow: hidden;
}

.letter-bar {
  display: flex;
  align-items: center;
  gap: 0.7rem;
  padding: 0.85rem clamp(1.25rem, 3vw, 2.25rem);
  border-bottom: 1px solid var(--hairline);
  background: rgba(0, 0, 0, 0.16);
}

.letter-mark { width: 38px; height: 24px; display: block; }

.letter-from {
  font-family: var(--mono);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--ink);
}

/* Headers. Label column sized in ch so the colons line up like a real header
   block rather than an arbitrary two-column grid. */
.headers {
  margin: 0;
  padding: clamp(1.25rem, 3vw, 1.75rem) clamp(1.25rem, 3vw, 2.25rem) 0;
  font-family: var(--mono);
  font-size: 0.8125rem;
  line-height: 1.95;
}

.headers > div { display: grid; grid-template-columns: 15ch minmax(0, 1fr); }

.headers dt { color: var(--ink-3); white-space: nowrap; }
.headers dt::after { content: ":"; }
.headers dd { margin: 0; color: var(--ink-2); }

/* RFC 822 separates headers from body with one empty line. That gap is the
   separator, so it gets no rule. */
.letter-body {
  padding: clamp(2.25rem, 5vw, 3.25rem) clamp(1.25rem, 3vw, 2.25rem)
           clamp(1.75rem, 4vw, 2.5rem);
}

/* The subject is a header like the others, so it keeps the header's type.
   Only its value is promoted. */
.subject-label {
  font-family: var(--mono);
  font-size: 0.8125rem;
  color: var(--ink-3);
  margin: 0 0 0.7rem;
}
.subject-label::after { content: ":"; }

.hero h1 {
  font-size: clamp(1.85rem, 3.9vw, 2.85rem);
  /* Looser than the other headings: tight tracking on a large size reads sharp,
     which is the opposite of what this face was chosen for. */
  letter-spacing: -0.012em;
  line-height: 1.16;
  margin-bottom: 1.6rem;
  max-width: 24ch;
  text-wrap: balance;
}

.lede {
  font-size: 1.0625rem;
  line-height: 1.65;
  color: var(--ink-2);
  max-width: 62ch;
  margin-bottom: 1.9rem;
}

/* --------------------------------------------------------------------------
   Command line with copy button
   -------------------------------------------------------------------------- */

.cmd {
  display: flex;
  align-items: stretch;
  gap: 0.5rem;
  background: var(--panel);
  border: 1px solid var(--hairline);
  border-radius: 8px;
  padding: 0.55rem 0.55rem 0.55rem 0.9rem;
  max-width: 100%;
  overflow: hidden;
}

.cmd code {
  flex: 1;
  min-width: 0;
  background: none;
  padding: 0;
  color: var(--ink);
  font-size: 0.8125rem;
  line-height: 1.9;
  overflow-x: auto;
  white-space: nowrap;
  scrollbar-width: thin;
}

.copy {
  flex: none;
  text-align: center;
  font-family: var(--mono);
  font-size: 0.75rem;
  color: var(--ink-2);
  background: var(--panel-hi);
  border: 1px solid var(--hairline-2);
  border-radius: 5px;
  padding: 0.3rem 0.7rem;
  cursor: pointer;
  transition: color .15s, border-color .15s;
}
.copy:hover { color: var(--ink); border-color: var(--arc-1); }

/* --------------------------------------------------------------------------
   Sections
   -------------------------------------------------------------------------- */

.section { padding-block: var(--bay); border-top: 1px solid var(--hairline); }

.section-head { margin-bottom: clamp(2rem, 4vw, 3rem); }

.label {
  font-family: var(--mono);
  font-size: 0.6875rem;
  letter-spacing: 0.24em;
  text-transform: uppercase;
  color: var(--ink-3);
  margin: 0 0 0.9rem;
}

.section-lede {
  color: var(--ink-2);
  max-width: var(--measure);
  margin-top: 1.1rem;
}

/* --------------------------------------------------------------------------
   Code blocks
   -------------------------------------------------------------------------- */

pre {
  margin: 0;
  font-size: 0.8125rem;
  line-height: 1.75;
  overflow-x: auto;
  scrollbar-width: thin;
  tab-size: 2;
}

pre.block {
  background: var(--panel);
  border: 1px solid var(--hairline);
  border-radius: 8px;
  padding: 1.1rem 1.25rem;
  color: var(--ink);
}

pre.wide { padding: 1.5rem; }

pre .p { color: var(--arc-4); user-select: none; }
pre .j { color: var(--arc-2); }
pre .k { color: var(--arc-1); }
pre .s { color: var(--arc-3); }

/* --------------------------------------------------------------------------
   The bridge: one command, two readers
   -------------------------------------------------------------------------- */

.switchbox { position: relative; }

/* The bridge itself. The switch sits on it, so choosing a reading is
   literally crossing from one side to the other. */
.bridge-rule {
  height: 3px;
  background: var(--arc);
  border-radius: 3px;
  opacity: 0.9;
  box-shadow: 0 0 22px rgba(213, 222, 198, 0.22);
}

.switch {
  position: relative;
  display: flex;
  width: fit-content;
  max-width: 100%;
  margin: -1.45rem auto 1.9rem;
  padding: 4px;
  background: var(--field);
  border: 1px solid var(--hairline-2);
  border-radius: 999px;
  /* Opens a gap in the bridge so the rule reads as passing behind. */
  box-shadow: 0 0 0 7px var(--field);
}

.switch label {
  font-family: var(--mono);
  font-size: 0.75rem;
  letter-spacing: 0.05em;
  color: var(--ink-3);
  padding: 0.55rem 1.15rem;
  border-radius: 999px;
  cursor: pointer;
  white-space: nowrap;
  transition: color .18s, background .18s;
}
.switch label:hover { color: var(--ink-2); }

#view-human:checked ~ .switch label[for="view-human"],
#view-agent:checked ~ .switch label[for="view-agent"] {
  color: var(--field);
  background: var(--arc-2);
}

#view-human:focus-visible ~ .switch label[for="view-human"],
#view-agent:focus-visible ~ .switch label[for="view-agent"] {
  outline: 2px solid var(--arc-1);
  outline-offset: -2px;
}

.pane { display: none; }

#view-human:checked ~ .pane-human,
#view-agent:checked ~ .pane-agent { display: block; }

.pane pre {
  background: var(--panel);
  border: 1px solid var(--hairline);
  border-radius: 8px;
  padding: 1.25rem 1.4rem;
}

.pane-note {
  margin: 0.9rem 0 0;
  font-size: 0.875rem;
  color: var(--ink-3);
  max-width: var(--measure);
}

/* --------------------------------------------------------------------------
   Contract
   -------------------------------------------------------------------------- */

.contract-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.3fr) minmax(0, 1fr);
  gap: clamp(2rem, 4vw, 3.5rem);
  align-items: start;
}

.contract pre.wide { margin-bottom: clamp(2rem, 4vw, 3rem); }

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

.codes li {
  display: grid;
  grid-template-columns: 12.5rem minmax(0, 1fr);
  gap: 1rem;
  padding: 0.6rem 0;
  border-bottom: 1px solid var(--hairline);
  font-size: 0.875rem;
}
.codes li:first-child { border-top: 1px solid var(--hairline); }
.codes code { background: none; padding: 0; color: var(--arc-3); }
.codes span { color: var(--ink-2); }

.contract-side { display: grid; gap: 1.5rem; }

.fact {
  background: var(--panel);
  border: 1px solid var(--hairline);
  border-radius: 8px;
  padding: 1.4rem 1.5rem;
}

.fact h3 {
  font-family: var(--mono);
  font-size: 0.6875rem;
  font-weight: 500;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--ink-3);
  margin-bottom: 1rem;
}

.exits {
  display: grid;
  grid-template-columns: 2rem 1fr;
  gap: 0.5rem 0.75rem;
  margin: 0;
  font-size: 0.9375rem;
}
.exits dt { font-family: var(--mono); color: var(--arc-1); }
.exits dd { margin: 0; color: var(--ink-2); }

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

.ticks li {
  position: relative;
  padding-left: 1.35rem;
  margin-bottom: 0.7rem;
  font-size: 0.9375rem;
  color: var(--ink-2);
}
.ticks li:last-child { margin-bottom: 0; }

.ticks li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.72em;
  width: 0.7rem;
  height: 1px;
  background: var(--arc-4);
}

/* --------------------------------------------------------------------------
   Feature and command grids
   -------------------------------------------------------------------------- */

.grid-2 { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: clamp(2rem, 4vw, 3.5rem); }
.grid-3 { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: clamp(1.75rem, 3.5vw, 3rem); }
.grid-4 { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: clamp(1.5rem, 3vw, 2.5rem); }

.features article h3 { margin-bottom: 0.6rem; }

.features article p {
  color: var(--ink-2);
  font-size: 0.9375rem;
  margin: 0;
}

.features article {
  padding-top: 1.15rem;
  border-top: 1px solid var(--hairline-2);
}

.verbs h3 {
  font-family: var(--mono);
  font-size: 0.6875rem;
  font-weight: 500;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--ink-3);
  padding-bottom: 0.85rem;
  margin-bottom: 0.85rem;
  border-bottom: 1px solid var(--hairline-2);
}

.verbs ul { list-style: none; margin: 0; padding: 0; }

.verbs li {
  font-size: 0.875rem;
  color: var(--ink-3);
  margin-bottom: 0.65rem;
}

.verbs code {
  background: none;
  padding: 0;
  color: var(--ink);
  font-size: 0.8125rem;
  margin-right: 0.3rem;
}

.commands-note {
  margin: clamp(2rem, 4vw, 3rem) 0 0;
  padding-top: 1.5rem;
  border-top: 1px solid var(--hairline);
  color: var(--ink-2);
  font-size: 0.9375rem;
}

/* --------------------------------------------------------------------------
   Install
   -------------------------------------------------------------------------- */

.step {
  font-family: var(--mono);
  font-size: 0.6875rem;
  font-weight: 500;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--ink-3);
  margin-bottom: 1rem;
}

.cmd-wide { max-width: 44rem; }

.install-req { margin: 0.85rem 0 clamp(2rem, 4vw, 3rem); }
.install pre.block { margin-bottom: 1rem; }
.install .muted { max-width: 52ch; }

/* --------------------------------------------------------------------------
   Closing and footer
   -------------------------------------------------------------------------- */

.closing-inner { text-align: center; }
.closing-inner h2 { margin-bottom: 0.9rem; }
.closing-inner .muted { margin-bottom: 2rem; }

.cta-row { display: flex; flex-wrap: wrap; gap: 0.75rem; justify-content: center; margin: 0; }

.btn {
  font-family: var(--mono);
  font-size: 0.8125rem;
  letter-spacing: 0.04em;
  color: var(--field);
  background: var(--arc-2);
  border: 1px solid var(--arc-2);
  border-radius: 6px;
  padding: 0.7rem 1.4rem;
  transition: opacity .15s;
}
.btn:hover { opacity: 0.88; text-decoration: none; }

.btn-quiet {
  color: var(--ink);
  background: none;
  border-color: var(--hairline-2);
}
.btn-quiet:hover { border-color: var(--arc-1); opacity: 1; }

.footer {
  border-top: 1px solid var(--hairline);
  padding-block: 2.5rem;
}

.footer-inner {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 0.5rem 2rem;
  font-size: 0.875rem;
  color: var(--ink-3);
}
.footer-inner p { margin: 0; }

/* --------------------------------------------------------------------------
   Narrow screens
   -------------------------------------------------------------------------- */

@media (max-width: 940px) {
  /* minmax(0,…) rather than 1fr: an auto-minimum track refuses to shrink below
     its widest unbreakable child and pushes the page into horizontal scroll. */
  .contract-grid { grid-template-columns: minmax(0, 1fr); }
  .grid-2 { grid-template-columns: minmax(0, 1fr); }
  .grid-3 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .grid-4 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .topnav a:not(.topnav-cta) { display: none; }
}

@media (max-width: 620px) {
  /* Header labels stack above their values: 13ch of label leaves nothing for
     the value at this width. */
  .headers > div { grid-template-columns: minmax(0, 1fr); }
  .headers { line-height: 1.5; }
  .headers > div + div { margin-top: 0.7rem; }
  .grid-3, .grid-4 { grid-template-columns: minmax(0, 1fr); }
  /* Too narrow to straddle the rule, so the pill drops below it instead of
     covering it entirely. */
  .switch { width: 100%; margin-top: 1.1rem; box-shadow: none; }
  .switch label {
    flex: 1;
    text-align: center;
    font-size: 0.6875rem;
    letter-spacing: 0;
    padding: 0.55rem 0.4rem;
  }
  .codes li { grid-template-columns: 1fr; gap: 0.15rem; }
  .footer-inner { flex-direction: column; }
}

/* --------------------------------------------------------------------------
   Reduced motion
   -------------------------------------------------------------------------- */

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
}