/* Proof & Machine - monochrome editorial */

:root {
  --ink: #0a0a0a;
  --paper: #ffffff;
  --grey-1: #f2f2f2;
  --grey-2: #d8d8d8;
  --grey-3: #6b6b6b;
  --rule: 1px solid var(--ink);
  --max: 1180px;
  --serif: "Iowan Old Style", "Palatino Linotype", Palatino, Georgia, "Times New Roman", serif;
  --sans: ui-sans-serif, "Helvetica Neue", Helvetica, Arial, system-ui, sans-serif;
  --mono: ui-monospace, "SFMono-Regular", Menlo, Consolas, monospace;
}

@media (prefers-color-scheme: dark) {
  :root {
    --ink: #f4f4f4;
    --paper: #070707;
    --grey-1: #161616;
    --grey-2: #2e2e2e;
    --grey-3: #a0a0a0;
  }
}

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

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

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 17px;
  line-height: 1.65;
}

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

a { color: inherit; text-underline-offset: 3px; text-decoration-thickness: 1px; }
a:hover { text-decoration-thickness: 2px; }

:focus-visible {
  outline: 3px solid var(--ink);
  outline-offset: 3px;
}

.skip {
  position: absolute;
  inset-inline-start: -9999px;
  top: 0;
  background: var(--ink);
  color: var(--paper);
  padding: 0.75rem 1rem;
  z-index: 50;
}
.skip:focus { inset-inline-start: 0; }

.wrap { width: min(100% - 2.5rem, var(--max)); margin-inline: auto; }
.narrow { width: min(100% - 2.5rem, 46rem); }

/* ---------- header ---------- */

.site-head {
  border-bottom: 2px solid var(--ink);
  position: sticky;
  top: 0;
  background: var(--paper);
  z-index: 40;
}

.head-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  min-height: 68px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  text-decoration: none;
  font-weight: 700;
  letter-spacing: -0.02em;
  font-size: 1.15rem;
}

.brand-mark {
  display: grid;
  place-items: center;
  width: 30px;
  height: 30px;
  background: var(--ink);
  color: var(--paper);
  font-family: var(--serif);
  font-size: 1.1rem;
  line-height: 1;
}

.amp { font-family: var(--serif); font-style: italic; padding-inline: 1px; }

.nav { display: flex; gap: 1.6rem; }
.nav a {
  text-decoration: none;
  font-size: 0.86rem;
  text-transform: uppercase;
  letter-spacing: 0.09em;
  padding-block: 0.4rem;
  border-bottom: 2px solid transparent;
}
.nav a:hover { border-bottom-color: var(--ink); }

.nav-toggle { display: none; }

@media (max-width: 760px) {
  .nav-toggle {
    display: grid;
    gap: 5px;
    background: none;
    border: var(--rule);
    padding: 9px 8px;
    cursor: pointer;
  }
  .nav-toggle span { display: block; width: 20px; height: 2px; background: var(--ink); }
  .nav {
    position: absolute;
    inset-inline: 0;
    top: 100%;
    background: var(--paper);
    border-bottom: 2px solid var(--ink);
    flex-direction: column;
    gap: 0;
    padding: 0.5rem 1.25rem 1.25rem;
    display: none;
  }
  .nav.open { display: flex; }
  .nav a { border-bottom: 1px solid var(--grey-2); padding-block: 0.9rem; }
}

/* ---------- hero ---------- */

.hero { border-bottom: var(--rule); padding-block: clamp(2.5rem, 7vw, 5rem); }

.hero h1 {
  font-family: var(--serif);
  font-weight: 400;
  letter-spacing: -0.03em;
  font-size: clamp(2.6rem, 8vw, 5.4rem);
  line-height: 0.98;
  margin: 0 0 1.25rem;
  max-width: 16ch;
}

.hero p {
  font-size: clamp(1.05rem, 2.2vw, 1.3rem);
  max-width: 54ch;
  color: var(--grey-3);
  margin: 0 0 2rem;
}

.hero-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem 2rem;
  font-family: var(--mono);
  font-size: 0.76rem;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--grey-3);
  border-top: 1px solid var(--grey-2);
  padding-top: 1rem;
}

/* ---------- sections ---------- */

.section { padding-block: clamp(2.5rem, 6vw, 4.5rem); border-bottom: var(--rule); }

.section-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 1rem;
  border-bottom: var(--rule);
  padding-bottom: 0.75rem;
  margin-bottom: 2rem;
}

.section-head h2 {
  margin: 0;
  font-size: 0.82rem;
  text-transform: uppercase;
  letter-spacing: 0.16em;
  font-weight: 700;
}

.section-head a { font-size: 0.82rem; text-transform: uppercase; letter-spacing: 0.1em; }

/* ---------- article cards ---------- */

.grid { display: grid; gap: 0; grid-template-columns: repeat(3, 1fr); }
.grid > * { border-inline-start: 1px solid var(--grey-2); padding: 1.6rem 1.6rem 2rem; }
.grid > *:first-child { border-inline-start: 0; padding-inline-start: 0; }

@media (max-width: 900px) {
  .grid { grid-template-columns: 1fr 1fr; }
  .grid > *:nth-child(3) { border-inline-start: 0; padding-inline-start: 0; }
}
@media (max-width: 620px) {
  .grid { grid-template-columns: 1fr; }
  .grid > * { border-inline-start: 0; padding-inline: 0; border-top: 1px solid var(--grey-2); }
  .grid > *:first-child { border-top: 0; }
}

.card .kicker,
.eyebrow {
  font-family: var(--mono);
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  color: var(--grey-3);
  margin: 0 0 0.7rem;
}

.card h3 {
  font-family: var(--serif);
  font-weight: 400;
  font-size: 1.5rem;
  line-height: 1.15;
  letter-spacing: -0.015em;
  margin: 0 0 0.6rem;
}
.card h3 a {
  text-decoration: none;
  background-image: linear-gradient(var(--ink), var(--ink));
  background-size: 0% 1px;
  background-repeat: no-repeat;
  background-position: 0 100%;
  transition: background-size .25s ease;
}
.card h3 a:hover { background-size: 100% 1px; }

.card p { margin: 0 0 0.9rem; color: var(--grey-3); }
.card time { font-family: var(--mono); font-size: 0.72rem; letter-spacing: 0.1em; text-transform: uppercase; color: var(--grey-3); }

/* lead story */
.lead-story {
  display: grid;
  grid-template-columns: 1.35fr 1fr;
  gap: 2.5rem;
  align-items: end;
  padding-bottom: 2.5rem;
  border-bottom: var(--rule);
  margin-bottom: 2.5rem;
}
.lead-story h3 {
  font-family: var(--serif);
  font-weight: 400;
  font-size: clamp(1.9rem, 4.5vw, 3rem);
  line-height: 1.05;
  letter-spacing: -0.025em;
  margin: 0.3rem 0 1rem;
}
.lead-story h3 a { text-decoration: none; }
.lead-story h3 a:hover { text-decoration: underline; }
@media (max-width: 820px) { .lead-story { grid-template-columns: 1fr; gap: 1.25rem; } }

.figure-block {
  border: var(--rule);
  aspect-ratio: 4 / 3;
  display: grid;
  place-items: center;
  background:
    repeating-linear-gradient(0deg, var(--grey-2) 0 1px, transparent 1px 28px),
    repeating-linear-gradient(90deg, var(--grey-2) 0 1px, transparent 1px 28px);
}
.figure-block span { font-family: var(--serif); font-size: clamp(3rem, 9vw, 6rem); }

/* index list */
.index-list { list-style: none; margin: 0; padding: 0; border-top: var(--rule); }
.index-list li { border-bottom: 1px solid var(--grey-2); }
.index-list a {
  display: grid;
  grid-template-columns: 5.5rem 1fr 9rem;
  gap: 1.5rem;
  align-items: baseline;
  padding: 1.35rem 0;
  text-decoration: none;
}
.index-list a:hover { background: var(--grey-1); }
.index-list .num { font-family: var(--mono); font-size: 0.75rem; color: var(--grey-3); letter-spacing: 0.1em; }
.index-list h3 { font-family: var(--serif); font-weight: 400; font-size: 1.4rem; line-height: 1.2; margin: 0 0 0.35rem; letter-spacing: -0.015em; }
.index-list p { margin: 0; color: var(--grey-3); font-size: 0.95rem; }
.index-list .meta { font-family: var(--mono); font-size: 0.7rem; text-transform: uppercase; letter-spacing: 0.12em; color: var(--grey-3); text-align: end; }
@media (max-width: 760px) {
  .index-list a { grid-template-columns: 1fr; gap: 0.4rem; }
  .index-list .meta { text-align: start; }
}

/* ---------- prose ---------- */

.post { padding-block: clamp(2.5rem, 6vw, 4rem); }

.post h1 {
  font-family: var(--serif);
  font-weight: 400;
  font-size: clamp(2.1rem, 6vw, 3.6rem);
  line-height: 1.03;
  letter-spacing: -0.028em;
  margin: 0 0 1rem;
}

.lede { font-size: 1.25rem; line-height: 1.5; color: var(--grey-3); margin: 0 0 1.5rem; }

.byline {
  font-family: var(--mono);
  font-size: 0.74rem;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--grey-3);
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  border-block: 1px solid var(--grey-2);
  padding-block: 0.85rem;
  margin-bottom: 2.5rem;
}

.prose { font-size: 1.08rem; line-height: 1.75; }
.prose > * + * { margin-top: 1.35rem; }
.prose h2 {
  font-family: var(--serif);
  font-weight: 400;
  font-size: 1.85rem;
  line-height: 1.15;
  letter-spacing: -0.02em;
  margin-top: 3rem;
  padding-top: 1rem;
  border-top: var(--rule);
}
.prose h3 { font-size: 1.15rem; margin-top: 2.2rem; letter-spacing: -0.01em; }
.prose blockquote {
  margin-inline: 0;
  padding-inline-start: 1.5rem;
  border-inline-start: 3px solid var(--ink);
  font-family: var(--serif);
  font-size: 1.3rem;
  line-height: 1.4;
}
.prose code { font-family: var(--mono); font-size: 0.88em; background: var(--grey-1); padding: 0.12em 0.35em; }
.prose pre { background: var(--grey-1); border: 1px solid var(--grey-2); padding: 1.1rem; overflow-x: auto; }
.prose pre code { background: none; padding: 0; }
.prose ul, .prose ol { padding-inline-start: 1.4rem; }
.prose li + li { margin-top: 0.5rem; }
.prose table { width: 100%; border-collapse: collapse; font-size: 0.95rem; display: block; overflow-x: auto; }
.prose th, .prose td { border: 1px solid var(--grey-2); padding: 0.6rem 0.7rem; text-align: start; vertical-align: top; }
.prose th { background: var(--grey-1); font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.08em; }
.prose hr { border: 0; border-top: var(--rule); margin-block: 2.5rem; }
.prose figure { margin: 2rem 0; }
.prose figcaption { font-size: 0.85rem; color: var(--grey-3); border-top: 1px solid var(--grey-2); padding-top: 0.5rem; margin-top: 0.5rem; }

.callout {
  border: var(--rule);
  padding: 1.25rem 1.4rem;
  background: var(--grey-1);
}

.rule { border: 0; border-top: var(--rule); margin-block: 2.5rem 1.5rem; }
.muted { color: var(--grey-3); }
.small { font-size: 0.9rem; }

.btn {
  display: inline-block;
  border: 2px solid var(--ink);
  padding: 0.7rem 1.3rem;
  text-decoration: none;
  font-size: 0.82rem;
  text-transform: uppercase;
  letter-spacing: 0.11em;
  font-weight: 700;
  background: var(--paper);
  color: var(--ink);
  cursor: pointer;
}
.btn:hover { background: var(--ink); color: var(--paper); }

/* ---------- page header (static pages) ---------- */

.page-head { border-bottom: var(--rule); padding-block: clamp(2.5rem, 6vw, 4rem); }
.page-head h1 {
  font-family: var(--serif);
  font-weight: 400;
  font-size: clamp(2.2rem, 6.5vw, 4rem);
  line-height: 1.02;
  letter-spacing: -0.028em;
  margin: 0.6rem 0 1rem;
}
.page-head p { font-size: 1.15rem; color: var(--grey-3); max-width: 58ch; margin: 0; }

.page-body { padding-block: clamp(2.5rem, 6vw, 4rem); }

/* ---------- solver tool ---------- */

.tool-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0; border: var(--rule); }
@media (max-width: 860px) { .tool-grid { grid-template-columns: 1fr; } }

.tool-pane { padding: 1.6rem; }
.tool-pane + .tool-pane { border-inline-start: 1px solid var(--grey-2); }
@media (max-width: 860px) {
  .tool-pane + .tool-pane { border-inline-start: 0; border-top: 1px solid var(--grey-2); }
}

.tool-pane h2 { font-size: 0.8rem; text-transform: uppercase; letter-spacing: 0.14em; margin: 0 0 1.1rem; }

.tabs { display: flex; flex-wrap: wrap; gap: 0; border: var(--rule); margin-bottom: 1.4rem; }
.tabs button {
  flex: 1 1 auto;
  background: var(--paper);
  color: var(--ink);
  border: 0;
  border-inline-start: 1px solid var(--grey-2);
  padding: 0.7rem 0.6rem;
  font: inherit;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.09em;
  cursor: pointer;
}
.tabs button:first-child { border-inline-start: 0; }
.tabs button[aria-selected="true"] { background: var(--ink); color: var(--paper); font-weight: 700; }

label { display: block; font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.1em; margin-bottom: 0.4rem; color: var(--grey-3); }

input[type="text"], input[type="number"], textarea, select {
  width: 100%;
  font-family: var(--mono);
  font-size: 16px;
  padding: 0.7rem 0.8rem;
  border: var(--rule);
  background: var(--paper);
  color: var(--ink);
  border-radius: 0;
}

.field + .field { margin-top: 1rem; }
.row { display: grid; grid-template-columns: repeat(3, 1fr); gap: 0.8rem; }

.steps { list-style: none; margin: 0; padding: 0; font-family: var(--mono); font-size: 0.92rem; }
.steps li { border-bottom: 1px dashed var(--grey-2); padding: 0.7rem 0; display: grid; grid-template-columns: 2rem 1fr; gap: 0.8rem; }
.steps li span:first-child { color: var(--grey-3); }
.result {
  border: 2px solid var(--ink);
  padding: 1rem 1.2rem;
  font-family: var(--mono);
  font-size: 1.15rem;
  margin-bottom: 1.2rem;
  word-break: break-word;
}
.result.error { background: var(--ink); color: var(--paper); }

.examples { display: flex; flex-wrap: wrap; gap: 0.5rem; margin-top: 0.9rem; }
.examples button {
  background: none;
  border: 1px solid var(--grey-2);
  padding: 0.35rem 0.6rem;
  font-family: var(--mono);
  font-size: 0.78rem;
  cursor: pointer;
  color: var(--ink);
}
.examples button:hover { border-color: var(--ink); }

.hidden { display: none; }

/* ---------- contact form ---------- */

.form-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.6fr) minmax(0, 1fr);
  gap: 0;
  border: var(--rule);
}
@media (max-width: 820px) { .form-grid { grid-template-columns: 1fr; } }

.form-main { padding: 1.8rem; }
.form-aside {
  padding: 1.8rem;
  border-inline-start: 1px solid var(--grey-2);
  background: var(--grey-1);
}
@media (max-width: 820px) {
  .form-aside { border-inline-start: 0; border-top: 1px solid var(--grey-2); }
}

.form-aside h2 {
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  margin: 0 0 0.7rem;
}
.form-aside .rule { margin-block: 1.6rem 1.4rem; }
.form-aside p { margin: 0 0 0.6rem; }

.mono-line {
  font-family: var(--mono);
  font-size: 0.95rem;
  border: var(--rule);
  background: var(--paper);
  padding: 0.6rem 0.7rem;
  word-break: break-all;
}

textarea { resize: vertical; min-height: 9rem; line-height: 1.6; }

.field .small { margin: 0.4rem 0 0; }

.honey {
  position: absolute;
  inset-inline-start: -9999px;
  width: 1px;
  height: 1px;
  overflow: hidden;
}

.form-status {
  border: 2px solid var(--ink);
  padding: 0.85rem 1rem;
  font-family: var(--mono);
  font-size: 0.9rem;
  margin: 1.2rem 0 0;
}
.form-status.error { background: var(--ink); color: var(--paper); }

button[type="submit"][disabled] { opacity: 0.5; cursor: default; }
button[type="submit"][disabled]:hover { background: var(--paper); color: var(--ink); }

/* ---------- search ---------- */

input[type="search"] {
  width: 100%;
  font-family: var(--mono);
  font-size: 16px;
  padding: 0.7rem 0.8rem;
  border: var(--rule);
  background: var(--paper);
  color: var(--ink);
  border-radius: 0;
  -webkit-appearance: none;
  appearance: none;
}

mark {
  background: var(--ink);
  color: var(--paper);
  padding: 0 0.15em;
}

#results .num { text-transform: uppercase; }
#results:empty { display: none; }

/* ---------- footer ---------- */

.site-foot { border-top: 2px solid var(--ink); padding-top: 3rem; }
.foot-grid { display: grid; grid-template-columns: 2fr 1fr 1fr; gap: 2.5rem; padding-bottom: 2.5rem; }
@media (max-width: 700px) { .foot-grid { grid-template-columns: 1fr; gap: 1.75rem; } }
.foot-brand { font-weight: 700; font-size: 1.1rem; margin: 0 0 0.5rem; letter-spacing: -0.02em; }
.site-foot h2 { font-size: 0.75rem; text-transform: uppercase; letter-spacing: 0.14em; margin: 0 0 0.8rem; }
.site-foot ul { list-style: none; margin: 0; padding: 0; }
.site-foot li + li { margin-top: 0.5rem; }
.site-foot a { font-size: 0.95rem; }
.foot-bottom { border-top: 1px solid var(--grey-2); padding-block: 1.25rem 2rem; }
.foot-bottom p { margin: 0; font-size: 0.85rem; }

@media (prefers-reduced-motion: reduce) {
  * { animation: none !important; transition: none !important; scroll-behavior: auto !important; }
}

@media print {
  .site-head, .site-foot, .nav, .skip { display: none; }
  body { font-size: 12pt; }
}