/* =============================================
   LinkOperator — Global Stylesheet (Light Theme)
   ============================================= */

/* --- Reset & Base --- */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
  background-color: #f9f9f7;
  color: #1a1a1a;
  line-height: 1.7;
}

/* --- Layout --- */
.container {
  max-width: 760px;
  margin: 0 auto;
  padding: 0 1.25rem;
}

/* --- Typography --- */
h1 {
  font-size: clamp(1.75rem, 4vw, 2.6rem);
  font-weight: 800;
  line-height: 1.2;
  color: #111111;
  margin-bottom: 1rem;
}

h2 {
  font-size: clamp(1.2rem, 3vw, 1.6rem);
  font-weight: 700;
  color: #111111;
  margin-bottom: 0.75rem;
  margin-top: 2.5rem;
}

p {
  margin-bottom: 1rem;
  color: #444444;
}

a {
  color: #2563eb;
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

ul {
  padding-left: 1.25rem;
  margin-bottom: 1rem;
}

ul li {
  margin-bottom: 0.5rem;
  color: #444444;
}

/* --- Header / Nav --- */
header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: #ffffff;
  border-bottom: 1px solid #e5e5e5;
  box-shadow: 0 1px 4px rgba(0,0,0,0.06);
  padding: 0 1.25rem;
}

header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 56px;
}

header nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
}

header nav strong {
  font-size: 1.1rem;
  color: #111111;
  letter-spacing: 0.03em;
}

header nav strong a {
  color: #111111 !important;
  text-decoration: none;
}

header nav ul {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  gap: 1.5rem;
}

header nav ul li a {
  color: #555555;
  font-size: 0.9rem;
  transition: color 0.2s;
}

header nav ul li a:hover {
  color: #111111;
  text-decoration: none;
}

/* --- Hero --- */
.hero {
  padding: 4rem 0 3rem;
  border-bottom: 1px solid #e8e8e8;
  background-color: #f9f9f7;
}

.hero h1 {
  margin-bottom: 0.75rem;
}

.hero p {
  font-size: 1.1rem;
  color: #666666;
  margin-bottom: 1.75rem;
  max-width: 560px;
}

/* --- Main Content --- */
main {
  padding: 2rem 1.25rem 3rem;
}

main section {
  margin-bottom: 2.5rem;
}

main section:first-child h2 {
  margin-top: 0;
}

/* --- Inline Code --- */
code {
  background-color: #f0f0f0;
  border: 1px solid #e0e0e0;
  border-radius: 4px;
  padding: 0.15em 0.45em;
  font-family: 'Courier New', monospace;
  font-size: 0.88em;
  color: #c0392b;
  word-break: break-all;
}

/* --- Button --- */
.btn {
  display: inline-block;
  background-color: #2563eb;
  color: #ffffff;
  padding: 0.65rem 1.4rem;
  border-radius: 6px;
  font-weight: 600;
  font-size: 0.95rem;
  text-decoration: none;
  transition: background-color 0.2s, transform 0.1s;
}

.btn:hover {
  background-color: #1d4ed8;
  text-decoration: none;
  transform: translateY(-1px);
}

/* --- Compare Block --- */
.compare {
  background-color: #f4f4f4;
  border: 1px solid #e0e0e0;
  border-left: 3px solid #2563eb;
  border-radius: 6px;
  padding: 1.25rem 1.5rem;
  font-family: 'Courier New', monospace;
  font-size: 0.95rem;
  color: #222222;
  white-space: pre-line;
  line-height: 2;
}

/* --- Tip Block --- */
.tip {
  background-color: #f0fdf4;
  border: 1px solid #bbf7d0;
  border-left: 3px solid #16a34a;
  border-radius: 6px;
  padding: 1rem 1.25rem;
  color: #166534;
  font-size: 0.95rem;
}

/* --- Warning Block --- */
.warn {
  background-color: #fffbeb;
  border: 1px solid #fde68a;
  border-left: 3px solid #d97706;
  border-radius: 6px;
  padding: 1rem 1.25rem;
  color: #92400e;
  font-size: 0.95rem;
}

/* --- CTA Strip --- */
.cta-strip {
  background-color: #1e3a5f;
  border-top: 1px solid #1e3a5f;
  border-bottom: 1px solid #1e3a5f;
  text-align: center;
  padding: 3rem 1.25rem;
}

.cta-strip h2 {
  margin-top: 0;
  margin-bottom: 1.25rem;
  color: #ffffff;
}

/* --- Checklist --- */
.checklist {
  list-style: none;
  padding: 0;
}

.checklist li {
  padding: 0.5rem 0;
  padding-left: 1.75rem;
  position: relative;
  color: #444444;
  border-bottom: 1px solid #eeeeee;
}

.checklist li::before {
  content: "✓";
  position: absolute;
  left: 0;
  color: #16a34a;
  font-weight: 700;
}

/* --- Table --- */
table {
  width: 100%;
  border-collapse: collapse;
  margin-bottom: 1.5rem;
  font-size: 0.9rem;
}

th {
  background-color: #f0f0f0;
  color: #111111;
  padding: 0.65rem 0.75rem;
  text-align: left;
  border-bottom: 2px solid #dddddd;
}

td {
  padding: 0.6rem 0.75rem;
  border-bottom: 1px solid #eeeeee;
  color: #444444;
}

tr:hover td {
  background-color: #f9f9f7;
}

/* --- Footer --- */
footer {
  text-align: center;
  padding: 2rem 1.25rem;
  font-size: 0.85rem;
  color: #999999;
  border-top: 1px solid #e5e5e5;
  background-color: #ffffff;
}

footer a {
  color: #999999;
}

footer a:hover {
  color: #444444;
}

/* --- Breadcrumb --- */
.breadcrumb {
  font-size: 0.82rem;
  color: #888888;
  padding: 0.6rem 0 0;
  margin-bottom: 0;
}

.breadcrumb a {
  color: #888888;
  text-decoration: none;
}

.breadcrumb a:hover {
  color: #2563eb;
  text-decoration: underline;
}

/* --- Concept Card Grid --- */
.card-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1rem;
  margin-top: 1.25rem;
  margin-bottom: 0;
  padding-left: 0;
  list-style: none;
}

.card-grid li {
  margin-bottom: 0;
  color: inherit;
}

.card-grid a {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  background-color: #ffffff;
  border: 1px solid #e5e5e5;
  border-radius: 8px;
  padding: 1rem 1.1rem;
  text-decoration: none;
  color: inherit;
  transition: border-color 0.2s, box-shadow 0.2s, transform 0.15s;
  height: 100%;
}

.card-grid a:hover {
  border-color: #2563eb;
  box-shadow: 0 2px 10px rgba(37,99,235,0.1);
  transform: translateY(-2px);
  text-decoration: none;
}

.card-grid .card-name {
  font-weight: 700;
  font-size: 0.92rem;
  color: #111111;
}

.card-grid .card-desc {
  font-size: 0.82rem;
  color: #666666;
  line-height: 1.4;
}

@media (max-width: 700px) {
  .card-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 420px) {
  .card-grid {
    grid-template-columns: 1fr;
  }
}

/* --- Responsive --- */
@media (max-width: 600px) {
  header nav ul {
    display: none;
  }

  .hero {
    padding: 2.5rem 0 2rem;
  }

  h1 {
    font-size: 1.6rem;
  }
}