:root {
  color-scheme: light;
  font-family: "Aptos", "Segoe UI Variable Text", "Segoe UI", system-ui, sans-serif;
  line-height: 1.6;
  --page-bg: #eee9e0;
  --page-glow: #f9f5ed;
  --surface: rgba(255, 253, 249, 0.9);
  --surface-strong: #fffdfa;
  --surface-muted: #f7f2ea;
  --text: #1a2028;
  --muted: #5a6675;
  --line: #d8d1c5;
  --line-strong: #c3b9a8;
  --accent: #175ea7;
  --accent-strong: #0d4277;
  --accent-soft: #e8f1ff;
  --shadow: 0 18px 42px rgba(43, 49, 60, 0.08);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  padding: 0;
  background:
    radial-gradient(circle at top, var(--page-glow) 0, #f4efe6 32%, var(--page-bg) 100%);
  color: var(--text);
}

header {
  padding: 18px 24px;
  border-bottom: 1px solid rgba(195, 185, 168, 0.75);
  background: rgba(255, 252, 247, 0.86);
  backdrop-filter: blur(14px);
}

header a {
  color: inherit;
  text-decoration: none;
  font-weight: 800;
  letter-spacing: 0.01em;
}

main {
  max-width: 1080px;
  margin: 0 auto;
  padding: 28px 20px 56px;
}

main > section {
  background: var(--surface);
  border: 1px solid rgba(216, 209, 197, 0.9);
  border-radius: 18px;
  padding: 1.35rem 1.5rem;
  box-shadow: var(--shadow);
}

main > section + section {
  margin-top: 1rem;
}

section > :first-child {
  margin-top: 0;
}

nav.breadcrumbs {
  display: inline-flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-bottom: 16px;
  padding: 0.45rem 0.8rem;
  border: 1px solid rgba(216, 209, 197, 0.95);
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.72);
  font-size: 0.82rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--muted);
}

nav.breadcrumbs a {
  color: inherit;
}

h1,
h2,
h3 {
  line-height: 1.18;
}

h1 {
  margin: 0 0 1rem;
  font-size: clamp(2rem, 4vw, 3rem);
  letter-spacing: -0.03em;
}

h2 {
  margin: 0 0 0.8rem;
  font-size: clamp(1.25rem, 2vw, 1.65rem);
  letter-spacing: -0.02em;
}

h3 {
  margin: 0 0 0.7rem;
  font-size: 1.05rem;
}

h4,
h5,
h6 {
  margin: 0 0 0.6rem;
}

p {
  margin: 0 0 1rem;
  max-width: 74ch;
}

ul,
ol,
dl {
  margin: 0.8rem 0 0;
  padding-left: 1.2rem;
}

li + li {
  margin-top: 0.4rem;
}

dt {
  font-weight: 700;
}

dd {
  margin: 0.3rem 0 0.9rem 0;
  color: var(--muted);
}

a {
  color: var(--accent);
  text-decoration-thickness: 1.25px;
  text-underline-offset: 0.16em;
}

a:hover {
  color: var(--accent-strong);
}

table,
.comparison-table,
.technical-specs-table,
.tech-specs {
  width: 100%;
  border-collapse: collapse;
  margin: 1rem 0 0;
  background: var(--surface-strong);
  border: 1px solid #d8dee7;
  border-radius: 14px;
  overflow: hidden;
}

caption {
  margin-bottom: 0.65rem;
  font-weight: 700;
  text-align: left;
}

thead th,
tr:first-child > th {
  background: #14263e;
  color: #f8fbff;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-size: 0.78rem;
}

th,
td {
  padding: 0.8rem 0.9rem;
  border: 1px solid #d8dee7;
  text-align: left;
  vertical-align: top;
}

tbody tr:nth-child(even) {
  background: #f8fafc;
}

img,
svg {
  max-width: 100%;
}

figure {
  margin: 1rem 0;
  padding: 0.85rem;
  border: 1px solid #d8dee7;
  border-radius: 16px;
  background: var(--surface-strong);
  box-shadow: var(--shadow);
}

figure img {
  display: block;
  width: 100%;
  height: auto;
  border-radius: 12px;
}

figcaption {
  margin-top: 0.75rem;
  color: var(--muted);
  font-size: 0.95rem;
}

pre,
code,
.formula,
.formula-block,
.math-block {
  font-family: "Cascadia Code", "JetBrains Mono", "SFMono-Regular", Consolas, monospace;
}

pre {
  padding: 1rem 1.1rem;
  overflow-x: auto;
  border-radius: 14px;
  border: 1px solid #253349;
  background: #121926;
  color: #eef4fb;
}

code {
  padding: 0.12rem 0.35rem;
  border-radius: 6px;
  background: #eef2f7;
  color: #163758;
}

.formula {
  display: block;
  margin: 1rem 0;
  padding: 0.9rem 1rem;
  border-left: 4px solid #2f6fb7;
  border-radius: 10px;
  background: #edf4fb;
  color: #0f2941;
}

.notice,
.warning-box,
.summary-box,
.pro-tip,
.tech-spec-box,
.formula-block,
.math-block {
  margin: 1rem 0;
  padding: 1rem 1.1rem;
  border-radius: 16px;
}

.notice {
  background: #fff6d6;
  border: 1px solid #ffe08a;
}

.warning-box {
  background: #fff5da;
  border: 1px solid #efce84;
}

.summary-box {
  background: #edf5ff;
  border: 1px solid #bfd4f3;
}

.pro-tip {
  background: #ebf8f0;
  border: 1px solid #9fceb0;
}

.tech-spec-box {
  background: #f4f6fa;
  border: 1px solid #d6dde8;
}

.formula-block,
.math-block {
  background: #121926;
  border: 1px solid #253349;
  color: #eef4fb;
}

.diagram-container {
  margin: 1.25rem 0;
  padding: 1.25rem;
  border: 1px solid #d6dde8;
  border-radius: 16px;
  background: #f7f9fc;
  overflow-x: auto;
}

.spec-grid,
.path-grid {
  display: grid;
  gap: 1rem;
}

.spec-grid {
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
}

.path-grid {
  grid-template-columns: repeat(3, minmax(0, 1fr));
  margin-top: 1rem;
}

.spec-card,
.path-card {
  background: var(--surface-strong);
  border: 1px solid rgba(216, 209, 197, 0.95);
  border-radius: 16px;
  padding: 1.2rem;
  box-shadow: var(--shadow);
}

.path-card--beginner {
  background: #edf9ef;
  border-left: 6px solid #2e7d32;
}

.path-card--installer {
  background: #fff5e7;
  border-left: 6px solid #d67a1f;
}

.path-card--engineer {
  background: #edf4ff;
  border-left: 6px solid #2561b8;
}

.path-card h3,
.spec-card h3 {
  margin-top: 0;
}

footer {
  margin-top: 1.25rem;
  padding-top: 1rem;
  border-top: 1px solid rgba(195, 185, 168, 0.9);
  font-size: 0.82rem;
  color: var(--muted);
}

footer p {
  margin: 0;
}

@media (max-width: 900px) {
  .path-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 720px) {
  header {
    padding: 16px 18px;
  }

  main {
    padding: 22px 16px 40px;
  }

  main > section {
    padding: 1.05rem 1rem;
    border-radius: 16px;
  }

  nav.breadcrumbs {
    font-size: 0.76rem;
  }

  table,
  .comparison-table,
  .technical-specs-table,
  .tech-specs {
    display: block;
    overflow-x: auto;
  }
}