/* 
 * Nhan Le - Personal Portfolio Stylesheet
 * Standard: Strict Monochrome (Black & White)
 * Rules: No colors, No shadows, No gradients. Pure typographic & structural hierarchy.
 */

:root {
  /* Font Families */
  --font-sans: 'Space Grotesk', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  --font-mono: 'JetBrains Mono', ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;

  /* Theme Tokens - Light Mode (Default) */
  --bg-primary: #ffffff;
  --bg-secondary: #f4f4f5;
  --bg-tertiary: #e4e4e7;
  --text-primary: #09090b;
  --text-secondary: #52525b;
  --text-muted: #71717a;
  --border-color: #e4e4e7;
  --border-strong: #09090b;
  --badge-bg: #f4f4f5;
  --badge-text: #09090b;
  --button-bg: #09090b;
  --button-text: #ffffff;
  --button-hover-bg: #27272a;
  --button-hover-text: #ffffff;

  /* Spacing System */
  --container-width: 960px;
  --section-spacing: 5rem;
}

[data-theme="dark"] {
  /* Theme Tokens - Dark Mode */
  --bg-primary: #09090b;
  --bg-secondary: #18181b;
  --bg-tertiary: #27272a;
  --text-primary: #fafafa;
  --text-secondary: #a1a1aa;
  --text-muted: #71717a;
  --border-color: #27272a;
  --border-strong: #fafafa;
  --badge-bg: #18181b;
  --badge-text: #fafafa;
  --button-bg: #fafafa;
  --button-text: #09090b;
  --button-hover-bg: #e4e4e7;
  --button-hover-text: #09090b;
}

/* Base Reset & Enforcement of Constraints */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  box-shadow: none !important;
  text-shadow: none !important;
  background-image: none !important;
}

html {
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.6;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  transition: background-color 0.15s ease, color 0.15s ease;
}

/* Layout Utilities */
.container {
  width: 100%;
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 0 1.5rem;
}

section {
  padding: var(--section-spacing) 0;
  border-bottom: 1px solid var(--border-color);
}

section:last-of-type {
  border-bottom: none;
}

/* Typography Hierarchy */
h1,
h2,
h3,
h4,
h5,
h6 {
  color: var(--text-primary);
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: -0.03em;
}

h1 {
  font-size: clamp(2.5rem, 5vw, 4rem);
  letter-spacing: -0.04em;
  line-height: 1.1;
}

h2 {
  font-size: clamp(1.5rem, 3vw, 2rem);
  margin-bottom: 1.5rem;
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

h2 .section-num {
  font-family: var(--font-mono);
  font-size: 1rem;
  font-weight: 400;
  color: var(--text-muted);
  border: 1px solid var(--border-color);
  padding: 0.1rem 0.5rem;
}

p {
  color: var(--text-secondary);
  margin-bottom: 1.25rem;
  font-size: 1.05rem;
  line-height: 1.7;
}

p:last-child {
  margin-bottom: 0;
}

a {
  color: var(--text-primary);
  text-decoration: underline;
  text-underline-offset: 4px;
  text-decoration-thickness: 1px;
  transition: opacity 0.15s ease;
}

a:hover {
  opacity: 0.7;
}

.mono {
  font-family: var(--font-mono);
}

/* Header & Navigation */
header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: var(--bg-primary);
  border-bottom: 1px solid var(--border-color);
  padding: 1.25rem 0;
  transition: background-color 0.15s ease, border-color 0.15s ease;
}

.nav-wrapper {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.brand {
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: 1.15rem;
  text-decoration: none;
  letter-spacing: -0.02em;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.brand-dot {
  display: inline-block;
  width: 8px;
  height: 8px;
  background-color: var(--text-primary);
  border-radius: 0;
  /* Pure square for sharp monochrome look */
}

.nav-controls {
  display: flex;
  align-items: center;
  gap: 1.5rem;
}

.nav-links {
  display: flex;
  list-style: none;
  gap: 1.5rem;
}

.nav-links a {
  font-family: var(--font-mono);
  font-size: 0.9rem;
  text-decoration: none;
  color: var(--text-secondary);
  transition: color 0.15s ease;
}

.nav-links a:hover {
  color: var(--text-primary);
  opacity: 1;
}

/* Theme Toggle Switcher */
.theme-btn {
  background: transparent;
  border: 1px solid var(--border-strong);
  color: var(--text-primary);
  font-family: var(--font-mono);
  font-size: 0.8rem;
  padding: 0.35rem 0.75rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.4rem;
  transition: background-color 0.15s ease, color 0.15s ease;
}

.theme-btn:hover {
  background-color: var(--text-primary);
  color: var(--bg-primary);
}

/* Hero Section */
.hero {
  padding-top: 5rem;
  padding-bottom: 5rem;
}

.hero-status {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--text-secondary);
  border: 1px solid var(--border-color);
  padding: 0.35rem 0.75rem;
  margin-bottom: 2rem;
}

.status-indicator {
  width: 6px;
  height: 6px;
  background-color: var(--text-primary);
}

.hero-title {
  margin-bottom: 1.5rem;
}

.hero-subtitle {
  font-size: 1.25rem;
  color: var(--text-secondary);
  max-width: 720px;
  margin-bottom: 2.5rem;
  line-height: 1.6;
}

.hero-ctas {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
}

/* Button Component System */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  font-family: var(--font-mono);
  font-size: 0.9rem;
  font-weight: 600;
  padding: 0.75rem 1.5rem;
  text-decoration: none;
  border: 1px solid var(--button-bg);
  background-color: var(--button-bg);
  color: var(--button-text);
  cursor: pointer;
  transition: background-color 0.15s ease, color 0.15s ease, border-color 0.15s ease;
}

.btn:hover {
  background-color: var(--button-hover-bg);
  color: var(--button-hover-text);
  opacity: 1;
}

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

.btn-secondary:hover {
  background-color: var(--text-primary);
  color: var(--bg-primary);
}

/* Badges / Outline Tags */
.tag-list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 1rem;
}

.tag {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  padding: 0.2rem 0.6rem;
  border: 1px solid var(--border-color);
  background-color: var(--badge-bg);
  color: var(--badge-text);
}

/* Content Grid Systems */
.grid-2 {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 2rem;
}

.grid-3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
}

/* Cards (Strict Monochrome Border Style) */
.card {
  border: 1px solid var(--border-color);
  padding: 1.75rem;
  background-color: var(--bg-primary);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  transition: border-color 0.15s ease;
}

.card:hover {
  border-color: var(--border-strong);
}

.card-header {
  margin-bottom: 1rem;
}

.card-meta {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-bottom: 0.5rem;
}

.card-title {
  font-size: 1.25rem;
  margin-bottom: 0.75rem;
}

.card-body {
  margin-bottom: 1.5rem;
  flex-grow: 1;
}

.card-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: 1rem;
  border-top: 1px dashed var(--border-color);
}

.card-link {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  font-weight: 600;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
}

.card-link::after {
  content: " →";
}

/* Principles & Skills */
.principle-item {
  border: 1px solid var(--border-color);
  padding: 1.5rem;
}

.quote-box {
  border: 1px solid var(--border-strong);
  padding: 1.75rem 2rem;
  margin-top: 2rem;
  background-color: var(--bg-secondary);
}

.quote-text {
  font-family: var(--font-mono);
  font-size: 0.95rem;
  line-height: 1.65;
  color: var(--text-primary);
  margin-bottom: 0.75rem;
}

.quote-author {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  text-align: right;
}

.principle-title {
  font-family: var(--font-mono);
  font-size: 1.1rem;
  margin-bottom: 0.5rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.skill-category {
  border: 1px solid var(--border-color);
  padding: 1.5rem;
}

.skill-category-title {
  font-family: var(--font-mono);
  font-size: 0.95rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--border-color);
  color: var(--text-muted);
}

.skill-item {
  font-family: var(--font-mono);
  font-size: 0.88rem;
  padding: 0.5rem 0;
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: center;
  gap: 0.5rem;
  border-bottom: 1px solid var(--border-color);
}

.skill-item:last-child {
  border-bottom: none;
}

.skill-name {
  color: var(--text-primary);
  font-weight: 500;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.skill-tag {
  font-size: 0.6rem;
  font-family: var(--font-mono);
  color: var(--text-muted);
  border: 1px solid var(--border-color);
  background-color: var(--badge-bg);
  padding: 0.15rem 0.45rem;
  white-space: nowrap;
  letter-spacing: 0.02em;
  text-align: right;
}

/* Experience Timeline */
.timeline {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.timeline-item {
  border: 1px solid var(--border-color);
  padding: 1.75rem;
  display: grid;
  grid-template-columns: 200px 1fr;
  gap: 1.5rem;
}

.timeline-period {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--text-muted);
}

.timeline-role {
  font-size: 1.2rem;
  margin-bottom: 0.25rem;
}

.timeline-company {
  font-family: var(--font-mono);
  font-size: 0.9rem;
  color: var(--text-secondary);
  margin-bottom: 0.75rem;
}

/* Contact Module */
.contact-box {
  border: 2px solid var(--border-strong);
  padding: 3rem 2rem;
  text-align: center;
  background-color: var(--bg-secondary);
}

.contact-email-wrapper {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.75rem;
  margin: 1.5rem 0;
  flex-wrap: wrap;
}

.contact-email-link {
  font-family: var(--font-mono);
  font-size: clamp(1.4rem, 3.5vw, 2.2rem);
  font-weight: 700;
  color: var(--text-primary);
  text-decoration: none;
  letter-spacing: -0.02em;
}

.contact-email-link:hover {
  opacity: 0.85;
}

.icon-btn {
  background: transparent;
  border: 1px solid var(--border-strong);
  color: var(--text-primary);
  padding: 0.5rem;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: background-color 0.15s ease, color 0.15s ease, transform 0.1s ease;
  line-height: 1;
}

.icon-btn:hover {
  background-color: var(--text-primary);
  color: var(--bg-primary);
}

.icon-btn:active {
  transform: scale(0.95);
}

/* Footer */
footer {
  padding: 3rem 0;
  border-top: 1px solid var(--border-color);
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--text-muted);
}

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

.footer-links {
  display: flex;
  gap: 1.5rem;
}

.footer-links a {
  color: var(--text-secondary);
  text-decoration: none;
}

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

/* Toast Feedback */
.toast {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  background-color: var(--text-primary);
  color: var(--bg-primary);
  font-family: var(--font-mono);
  font-size: 0.85rem;
  padding: 0.75rem 1.25rem;
  border: 1px solid var(--text-primary);
  z-index: 1000;
  opacity: 0;
  transform: translateY(10px);
  transition: opacity 0.2s ease, transform 0.2s ease;
  pointer-events: none;
}

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

/* Media Queries for Mobile Responsiveness */
@media (max-width: 768px) {
  :root {
    --section-spacing: 3.5rem;
  }

  .nav-links {
    display: none;
    /* Can be toggled if menu expanded, but keeping clean for mobile */
  }

  .grid-2,
  .grid-3 {
    grid-template-columns: 1fr;
  }

  .timeline-item {
    grid-template-columns: 1fr;
    gap: 0.5rem;
  }

  .hero-ctas {
    flex-direction: column;
    width: 100%;
  }

  .btn {
    width: 100%;
  }

  .footer-wrapper {
    flex-direction: column;
    align-items: flex-start;
  }
}