:root {
  --ink: #151719;
  --muted: #555f66;
  --paper: #ffffff;
  --soft: #f6f7f8;
  --line: #d8dde2;
  --accent: #24476b;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  font-family: Arial, Helvetica, sans-serif;
  line-height: 1.55;
}

a {
  color: inherit;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  background: rgba(255, 255, 255, 0.94);
  border-bottom: 1px solid var(--line);
}

.nav {
  width: min(1040px, calc(100% - 40px));
  min-height: 58px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}

.brand {
  color: var(--ink);
  font-weight: 700;
  text-decoration: none;
}

.nav-links {
  display: flex;
  gap: 18px;
  color: var(--muted);
  font-size: 0.93rem;
}

.nav-links a {
  text-decoration: none;
}

.nav-links a:hover {
  color: var(--accent);
}

.hero,
.section,
.footer {
  width: min(1040px, calc(100% - 40px));
  margin: 0 auto;
}

.hero {
  padding: 84px 0 64px;
  border-bottom: 1px solid var(--line);
}

.section {
  padding: 64px 0;
  border-bottom: 1px solid var(--line);
}

.label {
  margin: 0 0 10px;
  color: var(--accent);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

h1,
h2,
h3,
h4,
p {
  margin-top: 0;
}

h1 {
  max-width: 850px;
  margin-bottom: 20px;
  font-size: clamp(2.4rem, 6vw, 4.8rem);
  line-height: 1.02;
  letter-spacing: 0;
}

h2 {
  max-width: 800px;
  margin-bottom: 14px;
  font-size: clamp(1.7rem, 3vw, 2.65rem);
  line-height: 1.12;
  letter-spacing: 0;
}

h3 {
  margin-bottom: 8px;
  font-size: 1.12rem;
  line-height: 1.28;
}

h4 {
  margin-bottom: 12px;
  font-size: 0.96rem;
  line-height: 1.3;
}

.lead {
  max-width: 850px;
  color: var(--muted);
  font-size: 1.12rem;
}

.section-title {
  margin-bottom: 26px;
}

.section-title > p:not(.label) {
  max-width: 760px;
  color: var(--muted);
}

.equation-list {
  display: grid;
  gap: 18px;
}

.equation-block {
  padding: 24px;
  border: 1px solid var(--line);
  background: var(--soft);
}

.equation-block p,
.method-columns p,
.issue-row p,
.objective-card p {
  color: var(--muted);
}

.math-block {
  margin: 18px 0;
  padding: 18px;
  overflow-x: auto;
  border: 1px solid var(--line);
  background: var(--paper);
}

.paper-figure {
  margin: 0;
}

.paper-figure img {
  display: block;
  width: 100%;
  height: auto;
  border: 1px solid var(--line);
  background: var(--paper);
}

.paper-figure figcaption {
  margin-top: 10px;
  color: var(--muted);
  font-size: 0.9rem;
}

.paper-figure.compact img {
  max-height: 560px;
  object-fit: contain;
}

.figure-placeholder {
  min-height: 260px;
  margin: 0;
  display: grid;
  place-items: center;
  padding: 24px;
  border: 1px dashed #9ba6ae;
  background:
    linear-gradient(45deg, transparent 0 48%, rgba(36, 71, 107, 0.08) 48% 52%, transparent 52% 100%),
    var(--soft);
  text-align: center;
}

.figure-placeholder.large {
  min-height: 380px;
}

.figure-placeholder div {
  max-width: 460px;
  display: grid;
  gap: 8px;
}

.figure-placeholder strong {
  font-size: 1rem;
}

.figure-placeholder span {
  color: var(--muted);
}

.method-columns {
  margin-top: 24px;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px;
}

.method-columns article {
  padding: 22px;
  border: 1px solid var(--line);
}

.issue-table {
  border: 1px solid var(--line);
}

.issue-row {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  border-top: 1px solid var(--line);
}

.issue-row:first-child {
  border-top: 0;
}

.issue-row > div {
  padding: 22px;
}

.issue-row > div + div {
  border-left: 1px solid var(--line);
}

.issue-head {
  color: var(--paper);
  background: var(--accent);
  font-weight: 700;
}

.issue-head > div {
  padding: 14px 22px;
}

.warmstart-layout {
  display: grid;
  grid-template-columns: minmax(280px, 0.8fr) minmax(0, 1.2fr);
  gap: 28px;
  align-items: start;
}

.objective-card {
  padding: 24px;
  border: 1px solid var(--line);
  background: var(--soft);
}

.objective-card .math-block {
  font-size: 0.94rem;
}

.visualization-groups {
  display: grid;
  gap: 44px;
}

.method-group {
  display: grid;
  gap: 18px;
}

.method-group h3 {
  padding-bottom: 10px;
  border-bottom: 1px solid var(--line);
}

.comparison-examples {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 18px;
}

.comparison-card {
  padding: 18px;
  border: 1px solid var(--line);
  background: var(--soft);
}

.compare-slider {
  position: relative;
  aspect-ratio: 1 / 1;
  overflow: hidden;
  border: 1px dashed #9ba6ae;
  background:
    linear-gradient(45deg, transparent 0 48%, rgba(36, 71, 107, 0.08) 48% 52%, transparent 52% 100%),
    var(--paper);
}

.compare-image {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  background-color: var(--paper);
  background-repeat: no-repeat;
  background-size: contain;
  background-position: center;
}

.compare-image.placeholder-image::before {
  content: "Image placeholder";
  color: var(--muted);
  font-size: 0.86rem;
  font-weight: 700;
}

.compare-image.reconstruction {
  clip-path: inset(0 0 0 50%);
}

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

.science-objective {
  grid-column: 1 / -1;
}

.science-figures .paper-figure img {
  max-height: 300px;
  object-fit: contain;
}

.science-figures .scientific-comparison {
  grid-column: 1 / -1;
}

.science-figures .scientific-comparison img {
  max-height: none;
}

.paper-list {
  display: grid;
  gap: 10px;
}

.paper-list a {
  padding: 14px 16px;
  border: 1px solid var(--line);
  background: var(--soft);
  color: var(--accent);
  font-weight: 700;
  text-decoration: none;
}

.paper-list a:hover {
  border-color: var(--accent);
  background: var(--paper);
}

.compare-divider {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 50%;
  z-index: 2;
  width: 2px;
  background: var(--paper);
  box-shadow: 0 0 0 1px rgba(21, 23, 25, 0.16);
}

.compare-divider::before {
  content: "";
  position: absolute;
  top: 50%;
  left: 50%;
  width: 30px;
  height: 30px;
  transform: translate(-50%, -50%);
  border: 2px solid var(--paper);
  border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 2px 10px rgba(21, 23, 25, 0.22);
}

.compare-slider input[type="range"] {
  position: absolute;
  inset: 0;
  z-index: 3;
  width: 100%;
  height: 100%;
  margin: 0;
  opacity: 0;
  cursor: ew-resize;
}

.compare-labels {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  margin-top: 8px;
  color: var(--muted);
  font-size: 0.86rem;
  font-weight: 700;
}

.footer {
  padding: 32px 0 46px;
  color: var(--muted);
}

@media (max-width: 820px) {
  .nav {
    min-height: auto;
    align-items: flex-start;
    flex-direction: column;
    padding: 14px 0;
    gap: 10px;
  }

  .nav-links {
    width: 100%;
    overflow-x: auto;
    padding-bottom: 3px;
  }

  .hero {
    padding-top: 58px;
  }

  .method-columns,
  .issue-row,
  .warmstart-layout,
  .comparison-examples,
  .science-figures {
    grid-template-columns: 1fr;
  }

  .issue-row > div + div {
    border-left: 0;
    border-top: 1px solid var(--line);
  }
}

@media (min-width: 821px) and (max-width: 1100px) {
  .comparison-examples {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}