/* ==========================================================================
   QUANG MINH TRÍ - CORE DESIGN SYSTEM & BASE STYLES
   "Technology for a Brighter Tomorrow" | quangminhtri.com
   ========================================================================== */

:root {
  /* Brand Color Palette */
  --color-primary-navy: #05295E;
  --color-secondary-navy: #0E4889;
  --color-electric-blue: #1377C8;
  --color-light-blue: #8DC1DF;
  --color-subtle-blue: #F0F7FD;
  --color-primary-gold: #C5974D;
  --color-light-gold: #F2DBA5;
  --color-dark-gold: #966C26;

  /* Dark Sections & Elevation */
  --color-dark-bg-start: #031B3C;
  --color-dark-bg-end: #05295E;
  --color-dark-surface: #0A254C;
  --color-dark-border: rgba(141, 193, 223, 0.18);
  --color-dark-text-muted: #94A3B8;

  /* Neutral Spectrum */
  --color-bg: #FFFFFF;
  --color-bg-alt: #F8FAFC;
  --color-bg-subtle: #F1F5F9;
  --color-border: #E2E8F0;
  --color-border-hover: #CBD5E1;
  --color-text-main: #0F172A;
  --color-text-navy: #05295E;
  --color-text-muted: #52647E;
  --color-text-light: #64748B;
  --color-white: #FFFFFF;

  /* System Feedback */
  --color-success: #059669;
  --color-success-bg: #ECFDF5;
  --color-error: #DC2626;
  --color-error-bg: #FEF2F2;

  /* Typography */
  --font-sans: 'Plus Jakarta Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  --font-mono: 'JetBrains Mono', ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;

  /* Shadows */
  --shadow-sm: 0 1px 2px rgba(5, 41, 94, 0.05);
  --shadow-md: 0 4px 12px rgba(5, 41, 94, 0.08);
  --shadow-lg: 0 12px 28px rgba(5, 41, 94, 0.12);
  --shadow-xl: 0 20px 40px rgba(5, 41, 94, 0.16);
  --shadow-gold: 0 8px 24px rgba(197, 151, 77, 0.22);
  --shadow-glow: 0 0 40px rgba(19, 119, 200, 0.25);

  /* Layout Spacing */
  --container-max-width: 1280px;
  --container-narrow-width: 900px;
  --header-height: 80px;
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --radius-full: 9999px;

  /* Transitions */
  --transition-fast: 0.15s cubic-bezier(0.16, 1, 0.3, 1);
  --transition-normal: 0.25s cubic-bezier(0.16, 1, 0.3, 1);
  --transition-smooth: 0.4s cubic-bezier(0.16, 1, 0.3, 1);
}

/* Reset & Box Sizing */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

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

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  overflow-x: hidden;
  background-color: var(--color-bg);
}

/* Headings */
h1, h2, h3, h4, h5, h6 {
  color: var(--color-text-navy);
  font-weight: 700;
  line-height: 1.25;
  letter-spacing: -0.02em;
}

h1 { font-size: clamp(2.4rem, 5vw, 3.8rem); font-weight: 800; line-height: 1.15; }
h2 { font-size: clamp(1.85rem, 3.5vw, 2.75rem); }
h3 { font-size: clamp(1.35rem, 2.5vw, 1.85rem); }
h4 { font-size: 1.25rem; }
h5 { font-size: 1.1rem; }

p {
  color: var(--color-text-muted);
  font-size: 1.05rem;
  line-height: 1.7;
}

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

a:hover {
  color: var(--color-secondary-navy);
}

img, svg {
  max-width: 100%;
  height: auto;
  display: block;
}

button, input, select, textarea {
  font: inherit;
}

/* Accessibility Focus States */
:focus-visible {
  outline: 2px solid var(--color-electric-blue);
  outline-offset: 3px;
}

/* Utilities */
.container {
  width: 100%;
  max-width: var(--container-max-width);
  margin-left: auto;
  margin-right: auto;
  padding-left: clamp(1.25rem, 4vw, 2.5rem);
  padding-right: clamp(1.25rem, 4vw, 2.5rem);
}

.container-narrow {
  width: 100%;
  max-width: var(--container-narrow-width);
  margin-left: auto;
  margin-right: auto;
  padding-left: clamp(1.25rem, 4vw, 2.5rem);
  padding-right: clamp(1.25rem, 4vw, 2.5rem);
}

.section {
  padding-top: clamp(4.5rem, 8vw, 7.5rem);
  padding-bottom: clamp(4.5rem, 8vw, 7.5rem);
  position: relative;
}

.section-alt {
  background-color: var(--color-bg-alt);
  border-top: 1px solid var(--color-border);
  border-bottom: 1px solid var(--color-border);
}

.section-dark {
  background: linear-gradient(145deg, var(--color-dark-bg-start) 0%, var(--color-dark-bg-end) 100%);
  color: var(--color-white);
  border-top: 1px solid var(--color-dark-border);
  border-bottom: 1px solid var(--color-dark-border);
}

.section-dark h1,
.section-dark h2,
.section-dark h3,
.section-dark h4 {
  color: var(--color-white);
}

.section-dark p {
  color: var(--color-dark-text-muted);
}

/* Section Header Component */
.section-header {
  text-align: center;
  max-width: 760px;
  margin: 0 auto clamp(2.5rem, 5vw, 4rem) auto;
}

.section-header.text-left {
  text-align: left;
  margin-left: 0;
}

.section-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-family: var(--font-mono);
  font-size: 0.825rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--color-electric-blue);
  background-color: var(--color-subtle-blue);
  border: 1px solid rgba(19, 119, 200, 0.18);
  padding: 0.35rem 0.9rem;
  border-radius: var(--radius-full);
  margin-bottom: 1.25rem;
}

.section-dark .section-eyebrow {
  color: var(--color-light-gold);
  background-color: rgba(197, 151, 77, 0.12);
  border-color: rgba(242, 219, 165, 0.25);
}

.section-eyebrow.gold {
  color: var(--color-dark-gold);
  background-color: rgba(197, 151, 77, 0.12);
  border-color: rgba(197, 151, 77, 0.3);
}

.section-title {
  margin-bottom: 1rem;
}

.section-subtitle {
  font-size: 1.15rem;
  line-height: 1.6;
}

/* Reduced Motion Support */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}