/* ==========================================================================
   base.css - Design Tokens, Typography, Reset, and Foundational Styles
   luckylinux - Technical Engineering Blog
   ========================================================================== */

/* --- Google Fonts Import --- */
@import url('https://fonts.googleapis.com/css2?family=Fraunces:ital,opsz,wght@0,9..144,300..800;1,9..144,300..700&family=Inter:wght@400;500;600;700&family=JetBrains+Mono:ital,wght@0,400;0,500;0,600;1,400&family=Newsreader:ital,opsz,wght@0,6..72,400..700;1,6..72,400..600&display=swap');

/* --- Root Design Tokens (Light Theme by Default) --- */
:root {
  --font-heading: 'Fraunces', Georgia, 'Times New Roman', serif;
  --font-body: 'Newsreader', Georgia, 'Times New Roman', serif;
  --font-ui: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', 'SF Mono', Consolas, Monaco, monospace;

  /* Color Palette - Light Editorial */
  --bg-primary: #FAF6EE;
  --bg-surface: #F3ECE1;
  --bg-surface-raised: #FFFFFF;
  --bg-subtle: #EFE8DC;
  
  --text-primary: #1F1B16;
  --text-secondary: #5E5549;
  --text-muted: #847B6F;
  --text-faint: #B5AB9D;

  --border-color: rgba(45, 36, 26, 0.10);
  --border-subtle: rgba(45, 36, 26, 0.05);
  --border-hover: rgba(45, 36, 26, 0.22);

  /* Restrained Terracotta Accent */
  --accent: #B4532A;
  --accent-hover: #96421E;
  --accent-faint: rgba(180, 83, 42, 0.08);
  --accent-border: rgba(180, 83, 42, 0.25);
  --accent-contrast: #FFFFFF;

  /* Callout & Status Tones (Warm, subdued) */
  --color-note-bg: rgba(60, 90, 150, 0.06);
  --color-note-border: #3C5A96;
  --color-note-text: #2A4275;

  --color-tip-bg: rgba(47, 93, 80, 0.07);
  --color-tip-border: #2F5D50;
  --color-tip-text: #1E463C;

  --color-warning-bg: rgba(180, 83, 42, 0.07);
  --color-warning-border: #B4532A;
  --color-warning-text: #823819;

  /* Spacing Scale (8px system) */
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-8: 32px;
  --space-10: 40px;
  --space-12: 48px;
  --space-16: 64px;
  --space-20: 80px;
  --space-24: 96px;

  /* Layout Widths */
  --container-max: 1120px;
  --article-max: 68ch;
  --header-height: 64px;
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;

  /* Transitions */
  --transition-fast: 150ms cubic-bezier(0.16, 1, 0.3, 1);
  --transition-normal: 240ms cubic-bezier(0.16, 1, 0.3, 1);
  --theme-transition: background-color 260ms ease, color 260ms ease, border-color 260ms ease;
}

/* --- Dark Theme Tokens (Warm Charcoal, NEVER Pure Black) --- */
[data-theme="dark"] {
  --bg-primary: #141210;
  --bg-surface: #1E1B18;
  --bg-surface-raised: #25221E;
  --bg-subtle: #191613;

  --text-primary: #EDE6D8;
  --text-secondary: #ABA091;
  --text-muted: #7E7467;
  --text-faint: #544D43;

  --border-color: rgba(237, 230, 216, 0.10);
  --border-subtle: rgba(237, 230, 216, 0.05);
  --border-hover: rgba(237, 230, 216, 0.25);

  /* Terracotta slightly brightened for dark backgrounds */
  --accent: #D96B3D;
  --accent-hover: #E88358;
  --accent-faint: rgba(217, 107, 61, 0.12);
  --accent-border: rgba(217, 107, 61, 0.30);
  --accent-contrast: #141210;

  --color-note-bg: rgba(90, 130, 210, 0.10);
  --color-note-border: #6B8ECB;
  --color-note-text: #A4BFE8;

  --color-tip-bg: rgba(60, 130, 110, 0.10);
  --color-tip-border: #4D8F7D;
  --color-tip-text: #96D1C1;

  --color-warning-bg: rgba(217, 107, 61, 0.10);
  --color-warning-border: #D96B3D;
  --color-warning-text: #EDB29A;
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
  text-rendering: optimizeLegibility;
}

body {
  background-color: var(--bg-primary);
  color: var(--text-primary);
  font-family: var(--font-body);
  font-size: 1.125rem; /* ~18px */
  line-height: 1.7;
  font-feature-settings: "kern" 1, "liga" 1, "calt" 1;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: var(--theme-transition);
  position: relative;
}

/* --- Subtle Paper-Grain Overlay --- */
body::before {
  content: "";
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  pointer-events: none;
  z-index: 9999;
  opacity: 0.035;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 200 200' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='noiseFilter'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.8' numOctaves='3' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23noiseFilter)'/%3E%3C/svg%3E");
}

[data-theme="dark"] body::before {
  opacity: 0.025;
}

/* --- Selection Styling --- */
::selection {
  background-color: var(--accent);
  color: var(--accent-contrast);
}

/* --- Custom Scrollbar --- */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: var(--bg-primary);
}

::-webkit-scrollbar-thumb {
  background: var(--border-hover);
  border-radius: var(--radius-sm);
}

::-webkit-scrollbar-thumb:hover {
  background: var(--text-muted);
}

/* --- Skip to Main Content link (Accessibility) --- */
.skip-link {
  position: absolute;
  top: -100px;
  left: var(--space-4);
  background: var(--accent);
  color: var(--accent-contrast);
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-sm);
  font-family: var(--font-ui);
  font-size: 0.875rem;
  font-weight: 600;
  z-index: 10000;
  text-decoration: none;
  transition: top var(--transition-fast);
}

.skip-link:focus {
  top: var(--space-4);
  outline: 2px solid var(--text-primary);
  outline-offset: 2px;
}

/* --- Focus-visible styling --- */
:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
}

/* --- Typography Hierarchy --- */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: 600;
  color: var(--text-primary);
  line-height: 1.25;
  letter-spacing: -0.02em;
  text-wrap: balance;
  margin-bottom: var(--space-3);
}

h1 {
  font-size: clamp(2.2rem, 4.5vw, 3.5rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.15;
}

h2 {
  font-size: clamp(1.6rem, 3vw, 2.25rem);
  letter-spacing: -0.025em;
  line-height: 1.2;
}

h3 {
  font-size: clamp(1.25rem, 2.2vw, 1.5rem);
  letter-spacing: -0.015em;
}

h4 {
  font-size: 1.125rem;
}

p {
  margin-bottom: var(--space-4);
  text-wrap: pretty;
}

a {
  color: inherit;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
  transition: color var(--transition-fast), border-color var(--transition-fast);
}

code, kbd, samp, pre {
  font-family: var(--font-mono);
  font-size: 0.9em;
}

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

ul, ol {
  padding-left: var(--space-6);
  margin-bottom: var(--space-4);
}

li {
  margin-bottom: var(--space-1);
}

/* --- Utility Layout Classes --- */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin-left: auto;
  margin-right: auto;
  padding-left: var(--space-6);
  padding-right: var(--space-6);
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border-width: 0;
}

/* --- Fade-in-up animation on scroll --- */
.reveal-on-scroll {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity 500ms cubic-bezier(0.16, 1, 0.3, 1), transform 500ms cubic-bezier(0.16, 1, 0.3, 1);
}

.reveal-on-scroll.is-revealed {
  opacity: 1;
  transform: translateY(0);
}

@media (prefers-reduced-motion: reduce) {
  * {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
  .reveal-on-scroll {
    opacity: 1 !important;
    transform: none !important;
  }
}