/* ==========================================================================
   Design Tokens & CSS Variables
   ========================================================================== */
:root {
  /* Layout Dimensions */
  --header-height: 72px;
  --container-max-width: 980px;

  /* Color Palette - Light Mode */
  --bg-primary: #fafaf9;
  --bg-secondary: #f5f5f4;
  --bg-card: #ffffff;
  --bg-card-subtle: #fbfbfb;
  --bg-highlight: #f0f0ee;
  
  --border-subtle: #e7e5e4;
  --border-muted: #d6d3d1;
  --border-focus: #1c1917;

  --text-primary: #1c1917;
  --text-secondary: #44403c;
  --text-tertiary: #78716c;
  --text-muted: #a8a29e;

  /* Domain Badges (Soft, clear, and intentional) */
  --badge-ml-bg: #ecfdf5;
  --badge-ml-text: #065f46;
  --badge-ml-border: #a7f3d0;
  --badge-ml-dot: #10b981;

  --badge-sim-bg: #eff6ff;
  --badge-sim-text: #1e40af;
  --badge-sim-border: #bfdbfe;
  --badge-sim-dot: #3b82f6;

  --badge-cv-bg: #faf5ff;
  --badge-cv-text: #6b21a8;
  --badge-cv-border: #e9d5ff;
  --badge-cv-dot: #a855f7;

  --status-dot: #10b981;
  --status-dot-glow: rgba(16, 185, 129, 0.25);

  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-pill: 9999px;

  --shadow-subtle: 0 1px 3px rgba(0, 0, 0, 0.05), 0 1px 2px rgba(0, 0, 0, 0.03);
  --shadow-card: 0 4px 12px rgba(0, 0, 0, 0.04), 0 1px 3px rgba(0, 0, 0, 0.02);
  --shadow-hover: 0 12px 28px -6px rgba(0, 0, 0, 0.08), 0 6px 12px -4px rgba(0, 0, 0, 0.04);
  --shadow-portrait: 0 16px 36px -8px rgba(0, 0, 0, 0.12);

  --transition-fast: 0.15s ease;
  --transition-normal: 0.25s ease;
}

/* Dark Mode Overrides */
[data-theme="dark"] {
  --bg-primary: #0c0a09;
  --bg-secondary: #171513;
  --bg-card: #1c1917;
  --bg-card-subtle: #191715;
  --bg-highlight: #292524;

  --border-subtle: #292524;
  --border-muted: #44403c;
  --border-focus: #f5f5f4;

  --text-primary: #f5f5f4;
  --text-secondary: #d6d3d1;
  --text-tertiary: #a8a29e;
  --text-muted: #78716c;

  --badge-ml-bg: #064e3b25;
  --badge-ml-text: #6ee7b7;
  --badge-ml-border: #065f46;
  --badge-ml-dot: #34d399;

  --badge-sim-bg: #1e3a8a25;
  --badge-sim-text: #93c5fd;
  --badge-sim-border: #1e40af;
  --badge-sim-dot: #60a5fa;

  --badge-cv-bg: #581c8725;
  --badge-cv-text: #d8b4fe;
  --badge-cv-border: #6b21a8;
  --badge-cv-dot: #c084fc;

  --status-dot: #34d399;
  --status-dot-glow: rgba(52, 211, 153, 0.3);

  --shadow-subtle: 0 1px 3px rgba(0, 0, 0, 0.4);
  --shadow-card: 0 4px 14px rgba(0, 0, 0, 0.5);
  --shadow-hover: 0 16px 32px -8px rgba(0, 0, 0, 0.7);
  --shadow-portrait: 0 20px 40px -10px rgba(0, 0, 0, 0.8);
}

/* System Dark Mode Detection */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg-primary: #0c0a09;
    --bg-secondary: #171513;
    --bg-card: #1c1917;
    --bg-card-subtle: #191715;
    --bg-highlight: #292524;

    --border-subtle: #292524;
    --border-muted: #44403c;
    --border-focus: #f5f5f4;

    --text-primary: #f5f5f4;
    --text-secondary: #d6d3d1;
    --text-tertiary: #a8a29e;
    --text-muted: #78716c;

    --badge-ml-bg: #064e3b25;
    --badge-ml-text: #6ee7b7;
    --badge-ml-border: #065f46;
    --badge-ml-dot: #34d399;

    --badge-sim-bg: #1e3a8a25;
    --badge-sim-text: #93c5fd;
    --badge-sim-border: #1e40af;
    --badge-sim-dot: #60a5fa;

    --badge-cv-bg: #581c8725;
    --badge-cv-text: #d8b4fe;
    --badge-cv-border: #6b21a8;
    --badge-cv-dot: #c084fc;

    --status-dot: #34d399;
    --status-dot-glow: rgba(52, 211, 153, 0.3);

    --shadow-subtle: 0 1px 3px rgba(0, 0, 0, 0.4);
    --shadow-card: 0 4px 14px rgba(0, 0, 0, 0.5);
    --shadow-hover: 0 16px 32px -8px rgba(0, 0, 0, 0.7);
    --shadow-portrait: 0 20px 40px -10px rgba(0, 0, 0, 0.8);
  }
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  color-scheme: light dark;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  padding: 0;
  margin: 0;
  transition: background-color var(--transition-normal), color var(--transition-normal);
}

a {
  color: inherit;
  text-decoration: none;
  transition: color var(--transition-fast);
}

button {
  font-family: inherit;
  cursor: pointer;
  border: none;
  background: none;
}

:focus-visible {
  outline: 2px solid var(--border-focus);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

/* ==========================================================================
   Layout Containers & Section Viewport Sizing
   ========================================================================== */
.site-wrapper {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

.main-content {
  flex: 1;
}

/* Each section takes up at least one full page height and anchors below sticky header */
.page-section {
  min-height: calc(100vh - var(--header-height));
  scroll-margin-top: calc(var(--header-height) + 2rem);
  padding: clamp(3rem, 5vh, 4.5rem) clamp(1.25rem, 4vw, 2.5rem);
  display: flex;
  flex-direction: column;
  justify-content: center;
  border-bottom: 1px solid var(--border-subtle);
}

.section-container {
  max-width: var(--container-max-width);
  width: 100%;
  margin: 0 auto;
}

/* ==========================================================================
   Sticky Header & Navigation
   ========================================================================== */
.site-header {
  position: sticky;
  top: 0;
  height: var(--header-height);
  background-color: var(--bg-primary);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border-subtle);
  z-index: 100;
  display: flex;
  align-items: center;
  transition: background-color var(--transition-normal), border-color var(--transition-normal);
}

.header-container {
  max-width: var(--container-max-width);
  width: 100%;
  margin: 0 auto;
  padding: 0 clamp(1.25rem, 4vw, 2.5rem);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.brand-link {
  display: flex;
  flex-direction: column;
}

.brand-link .name {
  font-size: 1.15rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text-primary);
}

.brand-link .role-title {
  font-size: 0.8rem;
  color: var(--text-tertiary);
  font-weight: 500;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 1.5rem;
}

.nav-links {
  display: flex;
  gap: 1.35rem;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-secondary);
}

.nav-link {
  position: relative;
  padding: 0.35rem 0;
  transition: color var(--transition-fast);
}

.nav-link:hover {
  color: var(--text-primary);
}

.nav-link.active {
  color: var(--text-primary);
  font-weight: 600;
}

.nav-link.active::after {
  content: "";
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  height: 2px;
  background-color: var(--text-primary);
  border-radius: var(--radius-pill);
}

/* Theme Toggle */
.theme-toggle-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 38px;
  height: 38px;
  border-radius: var(--radius-sm);
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  color: var(--text-secondary);
  transition: all var(--transition-fast);
}

.theme-toggle-btn:hover {
  color: var(--text-primary);
  border-color: var(--border-muted);
}

.sun-icon { display: none; }
.moon-icon { display: block; }

[data-theme="dark"] .sun-icon { display: block; }
[data-theme="dark"] .moon-icon { display: none; }

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .sun-icon { display: block; }
  :root:not([data-theme="light"]) .moon-icon { display: none; }
}

/* ==========================================================================
   1. Hero Section (Two-Column Side-by-Side with Photo)
   ========================================================================== */
.hero-section {
  padding-top: clamp(2rem, 5vh, 4rem);
  padding-bottom: clamp(2.5rem, 6vh, 4.5rem);
}

.hero-grid {
  max-width: var(--container-max-width);
  width: 100%;
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1.18fr 0.82fr;
  align-items: center;
  gap: clamp(2rem, 5vw, 4rem);
}

.hero-text-col {
  display: flex;
  flex-direction: column;
}

.status-indicator {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  font-size: 0.825rem;
  font-weight: 500;
  color: var(--text-tertiary);
  padding: 0.35rem 0.8rem;
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-pill);
  width: fit-content;
  margin-bottom: 1.5rem;
}

.status-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background-color: var(--status-dot);
  box-shadow: 0 0 0 3px var(--status-dot-glow);
  display: inline-block;
  animation: pulse 2.5s infinite;
}

@keyframes pulse {
  0% { transform: scale(0.95); box-shadow: 0 0 0 0 var(--status-dot-glow); }
  70% { transform: scale(1); box-shadow: 0 0 0 6px rgba(16, 185, 129, 0); }
  100% { transform: scale(0.95); box-shadow: 0 0 0 0 rgba(16, 185, 129, 0); }
}

.hero-headline {
  font-size: clamp(2.25rem, 4vw, 3.25rem);
  font-weight: 800;
  letter-spacing: -0.035em;
  line-height: 1.15;
  color: var(--text-primary);
  margin-bottom: 1.25rem;
}

.hero-lead {
  font-size: clamp(1.1rem, 2vw, 1.25rem);
  font-weight: 500;
  line-height: 1.55;
  color: var(--text-primary);
  margin-bottom: 1rem;
}

.hero-subtext {
  font-size: 1rem;
  line-height: 1.65;
  color: var(--text-secondary);
  margin-bottom: 2rem;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.85rem;
}

/* Portrait Image Column */
.hero-image-col {
  display: flex;
  justify-content: center;
  align-items: center;
}

.portrait-frame {
  position: relative;
  width: 100%;
  max-width: 340px;
  aspect-ratio: 2 / 3;
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-portrait);
  border: 1px solid var(--border-subtle);
  background-color: var(--bg-card);
  transition: transform var(--transition-normal), box-shadow var(--transition-normal);
}

.portrait-frame:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-hover);
}

.portrait-img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: center 25%;
  display: block;
}

/* ==========================================================================
   Buttons & Links
   ========================================================================== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.9rem;
  font-weight: 600;
  padding: 0.65rem 1.25rem;
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
}

.btn-primary {
  background: var(--text-primary);
  color: var(--bg-primary);
  border: 1px solid var(--text-primary);
}

.btn-primary:hover {
  opacity: 0.92;
  transform: translateY(-1px);
}

.btn-secondary {
  background: var(--bg-secondary);
  color: var(--text-primary);
  border: 1px solid var(--border-subtle);
}

.btn-secondary:hover {
  border-color: var(--border-muted);
  transform: translateY(-1px);
}

.btn-subtle {
  background: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--border-subtle);
}

.btn-subtle:hover {
  color: var(--text-primary);
  border-color: var(--border-muted);
}

/* ==========================================================================
   2. Selected Engineering Work Section
   ========================================================================== */
.work-section {
  max-width: var(--container-max-width);
  margin: 0 auto;
  width: 100%;
  justify-content: flex-start; /* work has multiple large cards */
}

.section-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1.25rem;
  margin-bottom: 2.25rem;
  padding-bottom: 0.75rem;
  border-bottom: 1px solid var(--border-subtle);
}

.section-title {
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.025em;
  color: var(--text-primary);
}

/* Filter controls */
.filter-controls {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  background: var(--bg-secondary);
  padding: 0.3rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-subtle);
}

.filter-label {
  font-size: 0.775rem;
  font-weight: 600;
  color: var(--text-tertiary);
  padding: 0 0.5rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.filter-btn {
  padding: 0.35rem 0.75rem;
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--text-tertiary);
  border-radius: 4px;
  transition: all var(--transition-fast);
}

.filter-btn:hover {
  color: var(--text-primary);
}

.filter-btn.active {
  background: var(--bg-card);
  color: var(--text-primary);
  box-shadow: var(--shadow-subtle);
  font-weight: 600;
}

/* Project Cards */
.projects-list {
  display: flex;
  flex-direction: column;
  gap: 2.5rem;
}

.project-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: clamp(1.5rem, 3.5vw, 2.5rem);
  box-shadow: var(--shadow-card);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast), transform var(--transition-fast);
}

.project-card:hover {
  border-color: var(--border-muted);
  box-shadow: var(--shadow-hover);
}

.project-card.hidden {
  display: none;
}

.project-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
  margin-bottom: 1.15rem;
}

.project-meta {
  display: flex;
  align-items: center;
  gap: 0.85rem;
}

/* Clear, labeled domain badges with intentional indicators */
.project-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.775rem;
  font-weight: 600;
  padding: 0.28rem 0.75rem;
  border-radius: var(--radius-pill);
  letter-spacing: 0.015em;
}

.badge-dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  display: inline-block;
}

.badge-ml {
  background: var(--badge-ml-bg);
  color: var(--badge-ml-text);
  border: 1px solid var(--badge-ml-border);
}
.badge-ml .badge-dot {
  background: var(--badge-ml-dot);
}

.badge-simulation {
  background: var(--badge-sim-bg);
  color: var(--badge-sim-text);
  border: 1px solid var(--badge-sim-border);
}
.badge-simulation .badge-dot {
  background: var(--badge-sim-dot);
}

.badge-cv {
  background: var(--badge-cv-bg);
  color: var(--badge-cv-text);
  border: 1px solid var(--badge-cv-border);
}
.badge-cv .badge-dot {
  background: var(--badge-cv-dot);
}

.project-date {
  font-size: 0.825rem;
  font-family: var(--font-mono);
  color: var(--text-muted);
}

.project-links {
  display: flex;
  gap: 0.65rem;
}

.icon-link {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.825rem;
  font-weight: 500;
  color: var(--text-secondary);
  padding: 0.35rem 0.75rem;
  border-radius: var(--radius-sm);
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  transition: all var(--transition-fast);
}

.icon-link:hover {
  color: var(--text-primary);
  border-color: var(--border-muted);
}

.project-title {
  font-size: 1.35rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.35;
  margin-bottom: 0.85rem;
}

.project-title a {
  color: var(--text-primary);
}

.project-title a:hover {
  text-decoration: underline;
  text-decoration-thickness: 1.5px;
  text-underline-offset: 3px;
}

.project-summary {
  font-size: 1rem;
  line-height: 1.65;
  color: var(--text-secondary);
  margin-bottom: 1.5rem;
}

/* Metrics Grid */
.metrics-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 0.75rem;
  margin-bottom: 1.5rem;
}

.metric-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  padding: 0.85rem 1.15rem;
  display: flex;
  flex-direction: column;
}

.metric-value {
  font-size: 1.15rem;
  font-weight: 700;
  font-family: var(--font-mono);
  color: var(--text-primary);
  letter-spacing: -0.02em;
}

.metric-label {
  font-size: 0.75rem;
  color: var(--text-tertiary);
  margin-top: 0.25rem;
  line-height: 1.25;
}

/* Deep Dive Accordion */
.project-details {
  border-top: 1px solid var(--border-subtle);
  margin-top: 1.15rem;
  padding-top: 0.95rem;
  margin-bottom: 1.35rem;
}

.details-summary {
  display: flex;
  justify-content: space-between;
  align-items: center;
  cursor: pointer;
  padding: 0.5rem 0;
  user-select: none;
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-secondary);
  transition: color var(--transition-fast);
  list-style: none;
}

.details-summary::-webkit-details-marker {
  display: none;
}

.details-summary:hover {
  color: var(--text-primary);
}

.summary-chevron {
  font-size: 0.95rem;
  transition: transform var(--transition-fast);
}

details[open] .summary-chevron {
  transform: rotate(180deg);
}

.details-content {
  padding: 1.35rem 0 0.5rem 0;
  display: flex;
  flex-direction: column;
  gap: 1.35rem;
  font-size: 0.925rem;
  line-height: 1.65;
  color: var(--text-secondary);
  border-top: 1px dashed var(--border-subtle);
  margin-top: 0.5rem;
}

.details-section h4 {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 0.45rem;
  letter-spacing: -0.01em;
}

.details-section p {
  margin-bottom: 0.6rem;
}

.details-section p:last-child {
  margin-bottom: 0;
}

.details-section .inline-link {
  color: var(--text-primary);
  font-weight: 500;
  text-decoration: underline;
  text-decoration-thickness: 1.5px;
  text-underline-offset: 3px;
  transition: opacity var(--transition-fast);
}

.details-section .inline-link:hover {
  opacity: 0.8;
}

.details-section code {
  font-family: var(--font-mono);
  font-size: 0.825rem;
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  padding: 0.15rem 0.4rem;
  border-radius: 4px;
  color: var(--text-primary);
}

.details-section ul {
  padding-left: 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
}

.details-steps {
  padding-left: 1.35rem;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
  margin-top: 0.5rem;
}

.details-steps li {
  line-height: 1.5;
}

.details-section li strong {
  color: var(--text-primary);
}

/* Tech Stack Tags */
.tech-stack {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.tech-tag {
  font-size: 0.775rem;
  font-family: var(--font-mono);
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  color: var(--text-tertiary);
  padding: 0.25rem 0.6rem;
  border-radius: 4px;
}

/* ==========================================================================
   3. About Section (Direct, requested biography & experience)
   ========================================================================== */
.about-section {
  justify-content: center;
}

.about-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: clamp(2rem, 4vw, 3rem);
  box-shadow: var(--shadow-card);
  display: flex;
  flex-direction: column;
  gap: 2.25rem;
}

.about-text-content {
  font-size: 1.05rem;
  line-height: 1.75;
  color: var(--text-secondary);
  display: flex;
  flex-direction: column;
  gap: 1.35rem;
}

.about-text-content strong {
  color: var(--text-primary);
  font-weight: 600;
}

.about-highlights-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1.25rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border-subtle);
}

.highlight-item {
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.highlight-badge {
  font-size: 0.725rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-tertiary);
}

.highlight-title {
  font-size: 1rem;
  font-weight: 700;
  color: var(--text-primary);
}

.highlight-desc {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.45;
}

/* ==========================================================================
   4. Technical Skills Section
   ========================================================================== */
.skills-section {
  justify-content: center;
}

.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 1.5rem;
}

.skill-category {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  box-shadow: var(--shadow-card);
}

.category-title {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 1.25rem;
  padding-bottom: 0.75rem;
  border-bottom: 1px solid var(--border-subtle);
}

.category-icon {
  color: var(--text-muted);
  font-size: 0.85rem;
}

.skill-items {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.85rem;
  font-size: 0.9rem;
  line-height: 1.55;
  color: var(--text-secondary);
}

.skill-items strong {
  color: var(--text-primary);
  font-weight: 600;
}

/* ==========================================================================
   5. Contact Section
   ========================================================================== */
.contact-section {
  border-bottom: none;
  justify-content: center;
}

.contact-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: clamp(2.5rem, 5vw, 4rem);
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2rem;
  box-shadow: var(--shadow-card);
}

.contact-title {
  font-size: 2.25rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  color: var(--text-primary);
  margin-bottom: 0.75rem;
}

.contact-text {
  font-size: clamp(1.35rem, 2.4vw, 1.85rem);
  font-weight: 600;
  color: var(--text-primary);
  letter-spacing: -0.02em;
  margin-bottom: 0.5rem;
}

.contact-actions {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.85rem;
}

/* Contact Direct Channels Grid */
.contact-channels-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 0.85rem;
  width: 100%;
  max-width: 680px;
  margin-top: 0.25rem;
}

.contact-channel-item {
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  padding: 0.75rem 0.85rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.2rem;
  text-align: center;
  transition: border-color var(--transition-fast);
}

.contact-channel-item:hover {
  border-color: var(--border-muted);
}

.channel-label {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-tertiary);
}

.channel-value {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-primary);
  word-break: break-all;
}

.channel-value:hover {
  text-decoration: underline;
}

.contact-footer-note {
  font-size: 0.875rem;
  color: var(--text-tertiary);
  padding-top: 1rem;
  border-top: 1px dashed var(--border-subtle);
  width: 100%;
  max-width: 480px;
}

/* ==========================================================================
   Footer
   ========================================================================== */
.site-footer {
  margin-top: auto;
  padding: 2rem 0;
  border-top: 1px solid var(--border-subtle);
  background-color: var(--bg-primary);
}

.footer-container {
  max-width: var(--container-max-width);
  margin: 0 auto;
  padding: 0 clamp(1.25rem, 4vw, 2.5rem);
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
  font-size: 0.85rem;
  color: var(--text-tertiary);
}

.back-to-top {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  color: var(--text-secondary);
  font-weight: 500;
  transition: color var(--transition-fast);
}

.back-to-top:hover {
  color: var(--text-primary);
}

/* Toast Message */
.toast {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  background: var(--text-primary);
  color: var(--bg-primary);
  padding: 0.75rem 1.35rem;
  border-radius: var(--radius-sm);
  font-size: 0.875rem;
  font-weight: 500;
  box-shadow: var(--shadow-hover);
  opacity: 0;
  pointer-events: none;
  transform: translateY(10px);
  transition: opacity 0.2s ease, transform 0.2s ease;
  z-index: 1000;
}

.toast.show {
  opacity: 1;
  transform: translateY(0);
}

/* ==========================================================================
   Responsive Adaptations
   ========================================================================== */
@media (max-width: 860px) {
  .hero-grid {
    grid-template-columns: 1fr;
    text-align: left;
    gap: 2.5rem;
  }

  .hero-image-col {
    order: -1; /* Place portrait above or nicely centered */
    justify-content: flex-start;
  }

  .portrait-frame {
    max-width: 240px;
    aspect-ratio: 1 / 1; /* Square crop on mobile for balanced space */
  }

  .portrait-img {
    object-position: center 18%;
  }

  .header-actions {
    gap: 1rem;
  }

  .nav-links {
    gap: 1rem;
  }
}

@media (max-width: 640px) {
  :root {
    --header-height: auto;
  }

  .site-header {
    height: auto;
    padding: 1rem 0;
  }

  .header-container {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.75rem;
  }

  .header-actions {
    width: 100%;
    justify-content: space-between;
  }

  .filter-controls {
    width: 100%;
    overflow-x: auto;
    white-space: nowrap;
  }

  .metrics-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .about-highlights-grid {
    grid-template-columns: 1fr;
  }

  .toast {
    bottom: 1rem;
    right: 1rem;
    left: 1rem;
    text-align: center;
  }
}

/* Relevant coursework: keep course names readable within the existing skill card. */
.skill-items .coursework-list {
  margin: 0.75rem 0 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 0.5rem;
}
.skill-items .coursework-list li {
  margin: 0;
  padding: 0;
  line-height: 1.5;
}