/* ==========================================================================
   Design Tokens (Sleek Deep Midnight Blue Palette)
   ========================================================================== */
:root {
  --color-bg: #ffffff;
  --color-surface: #f9f9f9;
  --color-border: #e8e8e8;
  --color-text-main: #4a4a4a;
  --color-text-dark: #111111;
  --color-accent: #226db8;          /* Deep Midnight Blue Links */
  --color-highlight-bg: #f2f2f2;    
  --color-highlight-text: #111111;  
  --font-global: 'PretendardStd Variable', sans-serif; 
}

@media (prefers-color-scheme: dark) {
  :root {
    --color-bg: #000000;
    --color-surface: #161b22;
    --color-border: #21262d;
    --color-text-main: #c9d1d9;
    --color-text-dark: #f0f6fc;
    --color-accent: #85b7e8;        /* Midnight Marine Blue Links */
    --color-highlight-bg: #21262d;  
    --color-highlight-text: #f0f6fc;
  }
}

/* ==========================================================================
   Base Layout & Weight Standardizations (Zero Bold Rule)
   ========================================================================== */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

/* Universal reset ensuring no structural variations across pages */
*:not([class*="token"]) {
  font-weight: 400 !important;
}

body {
  background-color: var(--color-bg);
  color: var(--color-text-main);
  font-family: var(--font-global);
  font-size: 16px;
  line-height: 1.6;
  
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

/* ==========================================================================
   Precision Component Highlight (Replaces Old <strong> Tags)
   ========================================================================== */
strong, .highlight-token {
  background-color: var(--color-highlight-bg);
  color: var(--color-highlight-text);
  padding: 0.15rem 0.4rem;
  border-radius: 4px;
  font-size: 0.95em;
  display: inline-block;
  line-height: 1.2;
}

/* ==========================================================================
   Flat Header Setup (Fixed Pixel Scaling Engine)
   ========================================================================== */
.site-header {
  position: sticky;
  top: 0;
  background-color: var(--color-bg);
  z-index: 100;
  border-bottom: 1px solid var(--color-border);
  height: 60px;                  /* Fixed structural container height */
}

.nav-container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin: 0 auto;
  max-width: 800px;
  padding: 0 2rem;               /* Removed vertical padding to prevent scale shifting */
  height: 100%;                  /* Locks layout perfectly to the 60px header parent */
}

.nav-logo {
  color: var(--color-text-dark);
  font-size: 15px;               /* Scaled to match nav links exactly */
  letter-spacing: -0.5px;
  text-decoration: none;
  font-weight: 500 !important;
  line-height: 60px;             /* Line-height matching container height forces dead center */
  height: 60px;
}

.nav-logo span {
  color: var(--color-accent);
}

.nav-links {
  display: flex;
  gap: 1.5rem;
  height: 60px;
}

.nav-links a {
  color: var(--color-text-main);
  font-size: 15px;               /* Absolute, unshakeable pixel size */
  text-decoration: none;
  transition: color 0.2s ease;
  line-height: 60px;             /* Forces absolute text centring at 60px */
  height: 60px;
  display: inline-block;
}

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

.resume-link {
  color: var(--color-accent) !important;
}

/* ==========================================================================
   Content Grid & Headings
   ========================================================================== */
.main-content {
  margin: 0 auto;
  max-width: 800px;
  padding: 2.5rem 2rem 4rem 2rem;
  width: 100%;
  flex-grow: 1;
}

.page-section {
  margin-bottom: 2.5rem;
  scroll-margin-top: 5rem;
}

h1, h2, h3, h4 {
  color: var(--color-text-dark);
  letter-spacing: -0.5px;
}

h1 { font-size: 2.25rem; margin-bottom: 0.75rem; }
h2 { font-size: 0.85rem; text-transform: uppercase; letter-spacing: 1.5px; color: var(--color-text-main); margin-bottom: 1.25rem; }

.project-title {
  color: var(--color-accent) !important;
  font-size: 1.3rem;
  margin-bottom: 0.4rem;
}

h3 { font-size: 1.3rem; margin-bottom: 0.4rem; color: var(--color-text-dark); }

p { margin-bottom: 1rem; max-width: 680px; }
ul { margin-bottom: 1rem; padding-left: 1.25rem; }
li { margin-bottom: 0.35rem; }

/* ==========================================================================
   Project Cards Layout Array
   ========================================================================== */
.item-card { margin-bottom: 2rem; }
.item-header { display: flex; justify-content: space-between; align-items: baseline; margin-bottom: 0.25rem; }
.item-meta { color: var(--color-text-main); font-size: 0.9rem; opacity: 0.7; }
.project-links { display: flex; gap: 1.25rem; margin: 0.25rem 0 0.75rem 0; }
.item-tags { display: flex; gap: 0.5rem; margin-top: 0.75rem; flex-wrap: wrap; }

.tag {
  background-color: var(--color-surface);
  border-radius: 4px;
  color: var(--color-text-dark);
  font-size: 0.75rem;
  padding: 0.15rem 0.5rem;
  border: 1px solid var(--color-border);
}

.text-link {
  color: var(--color-accent);
  text-decoration: none;
}
.text-link:hover { text-decoration: underline; }

/* ==========================================================================
   Technical Components Layouts
   ========================================================================== */
.doc-vertical-nav {
  list-style: none;
  padding-left: 0;
  margin-bottom: 2rem;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.system-diagram {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 6px;
  padding: 1.75rem;
  margin: 1.25rem 0;
}

.diagram-node {
  background-color: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: 6px;
  padding: 0.75rem 1rem;
  flex: 1;
  text-align: center;
}

.active-node { border-color: var(--color-accent); }
.node-title { font-size: 0.9rem; color: var(--color-text-dark); margin-bottom: 0.15rem; }
.node-meta { font-size: 0.75rem; color: var(--color-text-main); opacity: 0.8; }
.diagram-arrow { font-size: 1.25rem; color: var(--color-text-main); opacity: 0.5; }

/* ==========================================================================
   Syntax Highlighting Base Containers
   ========================================================================== */
pre[class*="language-"] {
  background-color: var(--color-surface) !important;
  border: 1px solid var(--color-border) !important;
  margin: 1.25rem 0 !important;
  padding: 1rem !important;
  border-radius: 6px !important;
}
code[class*="language-"] {
  font-family: monospace !important;
  font-size: 0.9rem !important;
  text-shadow: none !important;
}

/* ==========================================================================
   Footer Component Shell
   ========================================================================== */
.site-footer {
  border-top: 1px solid var(--color-border);
  background-color: var(--color-bg);
  width: 100%;
}

.footer-container { 
  display: flex; 
  justify-content: space-between; 
  align-items: center; 
  margin: 0 auto; 
  max-width: 800px; 
  padding: 1.5rem 2rem; 
  font-size: 14px;              /* Enforced fixed absolute pixel value */
  color: var(--color-text-main); 
  opacity: 0.7; 
}

.footer-links { 
  display: flex; 
  gap: 1.25rem; 
  list-style: none; 
}

.footer-links a { 
  color: var(--color-text-main); 
  text-decoration: none; 
  transition: color 0.2s ease;
}

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

/* ==========================================================================
   Mobile Optimization Layout
   ========================================================================== */
@media (max-width: 650px) {
  .site-header {
    height: auto;
  }

  .nav-container {
    flex-direction: column;
    align-items: flex-start;
    padding: 0.75rem 1rem;
    gap: 0.5rem;
    height: auto;
  }

  .nav-logo {
    font-size: 17px;
    line-height: 1.5;
    height: auto;
  }

  .nav-links {
    flex-wrap: wrap;
    gap: 0.6rem;
    height: auto;
    width: 100%;
  }

  .nav-links a {
    font-size: 14px;
    line-height: 1.5;
    height: auto;
  }

  .main-content {
    padding: 2rem 1rem;
  }

  .item-header {
    flex-direction: column;
    gap: 0.15rem;
  }

  .footer-container {
    flex-direction: row;
    justify-content: space-between;
    align-items: center;
    padding: 1.25rem 1rem;
    font-size: 13px;
  }

  .footer-links {
    justify-content: flex-end;
  }

  .system-diagram { flex-direction: column; padding: 1.25rem; }
  .diagram-arrow { transform: rotate(90deg); margin: 0.15rem 0; }
  .diagram-node { width: 100%; }
}