:root {
  --bg-color: #ffffff;
  --text-color: #24292f;
  --heading-color: #0f172a;
  --link-color: #0969da;
  --link-hover: #0550ae;
  --border-color: #d0d7de;
  --code-bg: #f6f8fa;
  --meta-color: #57606a;
  --tag-bg: #eaeef2;
  --tag-color: #32383f;
  --font-main: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans", Helvetica, Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, SF Mono, Menlo, Consolas, Liberation Mono, monospace;
}

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

body {
  font-family: var(--font-main);
  background-color: var(--bg-color);
  color: var(--text-color);
  line-height: 1.65;
  margin: 0;
  padding: 0;
  overflow-wrap: break-word;
}

.container {
  max-width: 820px;
  width: 100%;
  margin: 0 auto;
  padding: 24px 20px;
}

/* Header & Nav */
header.site-header {
  border-bottom: 1px solid var(--border-color);
  margin-bottom: 2rem;
  padding-bottom: 1rem;
}

.header-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
}

.site-title {
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--heading-color);
  text-decoration: none;
}

.site-title:hover {
  text-decoration: none;
}

nav.site-nav a {
  margin-left: 1rem;
  font-weight: 500;
  color: var(--meta-color);
}

nav.site-nav a:hover {
  color: var(--link-color);
  text-decoration: none;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  line-height: 1.3;
  margin-top: 1.8em;
  margin-bottom: 0.8em;
  color: var(--heading-color);
}

h1 { font-size: 2.1rem; margin-top: 0.5em; }
h2 { font-size: 1.55rem; border-bottom: 1px solid var(--border-color); padding-bottom: 0.3em; }
h3 { font-size: 1.25rem; }

a {
  color: var(--link-color);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
  color: var(--link-hover);
}

img {
  max-width: 100%;
  height: auto;
  border-radius: 6px;
  display: block;
  margin: 1.5em auto;
}

blockquote {
  border-left: 4px solid var(--link-color);
  margin: 1.5em 0;
  padding: 0.8em 1.2em;
  color: #4b5563;
  background: #f8fafc;
  border-radius: 0 4px 4px 0;
}

/* Code & Pre */
pre {
  background-color: var(--code-bg);
  padding: 1em;
  border-radius: 6px;
  overflow-x: auto;
  border: 1px solid var(--border-color);
  margin: 1.5em 0;
  font-size: 0.9em;
  line-height: 1.45;
}

code {
  font-family: var(--font-mono);
  font-size: 0.88em;
  background-color: var(--code-bg);
  padding: 0.2em 0.4em;
  border-radius: 4px;
}

pre code {
  background-color: transparent;
  padding: 0;
  border-radius: 0;
  font-size: inherit;
}

/* Tables */
table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.5em 0;
  display: block;
  overflow-x: auto;
}

th, td {
  border: 1px solid var(--border-color);
  padding: 8px 14px;
  text-align: left;
}

th {
  background-color: #f6f8fa;
  font-weight: 600;
}

/* Metadata & Tags */
.post-header {
  margin-bottom: 2rem;
}

.post-meta {
  color: var(--meta-color);
  font-size: 0.9rem;
  margin-top: 0.5rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.8rem;
  align-items: center;
}

.tags {
  display: inline-flex;
  flex-wrap: wrap;
  gap: 0.4rem;
}

.tag {
  display: inline-block;
  background-color: var(--tag-bg);
  color: var(--tag-color);
  padding: 0.15rem 0.5rem;
  border-radius: 12px;
  font-size: 0.78rem;
  font-weight: 500;
}

/* Post list on Homepage */
.post-list {
  list-style: none;
  padding: 0;
  margin: 1.5rem 0;
}

.post-item {
  padding: 1.2rem 0;
  border-bottom: 1px solid var(--border-color);
}

.post-item-title {
  font-size: 1.25rem;
  font-weight: 600;
  margin: 0 0 0.3rem 0;
}

.post-item-title a {
  color: var(--heading-color);
}

.post-item-title a:hover {
  color: var(--link-color);
}

.post-item-meta {
  color: var(--meta-color);
  font-size: 0.85rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  align-items: center;
}

.post-item-category {
  font-weight: 600;
  text-transform: uppercase;
  font-size: 0.72rem;
  letter-spacing: 0.05em;
  color: #64748b;
  background: #f1f5f9;
  padding: 2px 6px;
  border-radius: 4px;
}

/* Footnotes */
.footnote {
  margin-top: 3rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border-color);
  font-size: 0.88rem;
  color: #4b5563;
}

.footnote-ref {
  font-size: 0.75em;
  vertical-align: super;
  padding: 0 2px;
}

/* Mermaid & MathJax */
.mermaid {
  text-align: center;
  margin: 2em 0;
  overflow-x: auto;
}

.mermaid svg {
  max-width: 100%;
  height: auto;
}

mjx-container {
  overflow-x: auto;
  overflow-y: hidden;
  max-width: 100%;
}

/* Footer */
footer.site-footer {
  margin-top: 4rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border-color);
  text-align: center;
  color: var(--meta-color);
  font-size: 0.85rem;
}