*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --black: #111111;
  --mid: #555555;
  --light: #999999;
  --rule: #e0e0e0;
  --bg: #ffffff;
}

html { scroll-behavior: smooth; }

body {
  font-family: 'Inter', sans-serif;
  background: var(--bg);
  color: var(--black);
  line-height: 1.6;
}

/* ── NAV ── */
nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1.5rem 3rem;
  border-bottom: 1px solid var(--rule);
  position: sticky;
  top: 0;
  background: #fff;
  z-index: 100;
}

.nav-name {
  font-family: 'Playfair Display', serif;
  font-size: 1.1rem;
  color: var(--black);
  text-decoration: none;
}

.nav-links {
  display: flex;
  gap: 2rem;
  list-style: none;
  flex-wrap: wrap;
}

.nav-links a {
  font-size: 0.8rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--mid);
  text-decoration: none;
  transition: color 0.2s;
}

.nav-links a:hover, .nav-links a.active { color: var(--black); }

hr {
  border: none;
  border-top: 1px solid var(--rule);
  max-width: 900px;
  margin: 0 auto;
}

.section {
  max-width: 900px;
  margin: 0 auto;
  padding: 4rem 3rem;
}

.section h2 {
  font-family: 'Playfair Display', serif;
  font-size: clamp(1.75rem, 3.5vw, 2.25rem);
  font-weight: 700;
  letter-spacing: -0.01em;
  margin-bottom: 1.5rem;
}

.section-label {
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--light);
  margin-bottom: 0.5rem;
}

/* ── ACCORDION ── */
.accordion { border-top: 1px solid var(--rule); }
.accordion-item { border-bottom: 1px solid var(--rule); }

.accordion-trigger {
  width: 100%;
  background: none;
  border: none;
  cursor: pointer;
  padding: 1.5rem 0;
  display: flex;
  justify-content: space-between;
  align-items: center;
  text-align: left;
}

.accordion-trigger h3 {
  font-size: 1rem;
  font-weight: 500;
  color: var(--black);
}

.accordion-trigger .client-tag {
  font-size: 0.75rem;
  color: var(--light);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  margin-bottom: 0.2rem;
}

.accordion-icon {
  font-size: 1.4rem;
  font-weight: 300;
  color: var(--mid);
  flex-shrink: 0;
  margin-left: 1rem;
  transition: transform 0.25s;
  line-height: 1;
}

.accordion-item.open .accordion-icon { transform: rotate(45deg); }

.accordion-body {
  display: none;
  padding: 0 0 1.75rem;
  font-size: 0.925rem;
  color: var(--mid);
  line-height: 1.75;
  max-width: 640px;
}

.accordion-item.open .accordion-body { display: block; }

/* ── FOOTER ── */
footer {
  border-top: 1px solid var(--rule);
  padding: 1.5rem 3rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.78rem;
  color: var(--light);
  max-width: 100%;
}

/* ── BACK LINK ── */
.back-link {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.8rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--mid);
  text-decoration: none;
  padding: 2rem 3rem 0;
  max-width: 900px;
  margin: 0 auto;
  display: block;
}

.back-link:hover { color: var(--black); }

/* ── CASE STUDY PAGE ── */
.cs-hero {
  max-width: 900px;
  margin: 0 auto;
  padding: 3rem 3rem 2rem;
  border-bottom: 1px solid var(--rule);
}

.cs-hero h1 {
  font-family: 'Playfair Display', serif;
  font-size: clamp(2rem, 5vw, 3rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.1;
  margin-bottom: 1rem;
  max-width: 700px;
}

.cs-hero .subtitle {
  font-size: 1rem;
  color: var(--mid);
  max-width: 560px;
  line-height: 1.6;
}

.cs-meta {
  display: flex;
  gap: 3rem;
  margin-top: 2rem;
  flex-wrap: wrap;
}

.cs-meta-item .label {
  font-size: 0.72rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--light);
  margin-bottom: 0.2rem;
}

.cs-meta-item .value {
  font-size: 1rem;
  font-weight: 600;
  color: var(--black);
}

.cs-body {
  max-width: 900px;
  margin: 0 auto;
  padding: 3rem;
}

.cs-body h3 {
  font-family: 'Playfair Display', serif;
  font-size: 1.25rem;
  font-weight: 700;
  margin: 2.5rem 0 0.75rem;
  color: var(--black);
}

.cs-body h3:first-child { margin-top: 0; }

.cs-body p {
  font-size: 0.975rem;
  color: var(--mid);
  line-height: 1.8;
  margin-bottom: 1.25rem;
  max-width: 680px;
}

.cs-body p strong { color: var(--black); }

.result-box {
  background: #f7f7f7;
  border-left: 3px solid var(--black);
  padding: 1.5rem 1.75rem;
  margin: 2rem 0;
  border-radius: 0 8px 8px 0;
}

.result-box .result-num {
  font-family: 'Playfair Display', serif;
  font-size: 2.5rem;
  font-weight: 700;
  line-height: 1;
  margin-bottom: 0.3rem;
}

.result-box .result-label {
  font-size: 0.9rem;
  color: var(--mid);
}

.next-case {
  max-width: 900px;
  margin: 0 auto;
  padding: 3rem;
  border-top: 1px solid var(--rule);
}

.next-case p {
  font-size: 0.75rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--light);
  margin-bottom: 0.5rem;
}

.next-case a {
  font-family: 'Playfair Display', serif;
  font-size: 1.5rem;
  color: var(--black);
  text-decoration: none;
  border-bottom: 1px solid var(--black);
  transition: opacity 0.2s;
}

.next-case a:hover { opacity: 0.5; }

/* ── CARD GRID ── */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 1px;
  background: var(--rule);
  border: 1px solid var(--rule);
  border-radius: 4px;
  overflow: hidden;
}

.card {
  background: #fff;
  padding: 1.75rem;
  text-decoration: none;
  display: block;
  transition: background 0.15s;
}

.card:hover { background: #f9f9f9; }

.card .card-label {
  font-size: 0.72rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--light);
  margin-bottom: 0.5rem;
}

.card .card-num {
  font-family: 'Playfair Display', serif;
  font-size: 1.75rem;
  font-weight: 700;
  line-height: 1;
  color: var(--black);
  margin-bottom: 0.4rem;
}

.card .card-title {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--black);
  margin-bottom: 0.4rem;
}

.card .card-desc {
  font-size: 0.82rem;
  color: var(--mid);
  line-height: 1.55;
}

.card .card-arrow {
  font-size: 0.8rem;
  color: var(--light);
  margin-top: 1rem;
  display: block;
}

/* ── RESPONSIVE ── */
@media (max-width: 700px) {
  nav { padding: 1.25rem 1.5rem; }
  .nav-links { gap: 1.25rem; }
  .section { padding: 3rem 1.5rem; }
  .cs-hero { padding: 2rem 1.5rem; }
  .cs-body { padding: 2rem 1.5rem; }
  .back-link { padding: 1.5rem 1.5rem 0; }
  .next-case { padding: 2rem 1.5rem; }
  footer { padding: 1.5rem; flex-direction: column; gap: 0.5rem; text-align: center; }
}