/* ============================================================
   BASE.CSS — Design tokens, reset, typography, layout
   Imported first by every page.
============================================================ */

/* ------------------------------------------------------------
   DESIGN TOKENS
   Edit these variables to retheme the entire site.
------------------------------------------------------------ */
:root {
  /* Brand */
  --indigo:        #6f00ff;
  --indigo-hover:  #5500cc;
  --indigo-faint:  rgba(111, 0, 255, 0.06);
  --indigo-border: rgba(111, 0, 255, 0.18);

  /* Surface — white-based light theme */
  --bg:            #ffffff;
  --bg-off:        #f7f7f8;   /* very light gray for alternating sections */
  --bg-subtle:     #f0f0f2;   /* used for code blocks, pills */

  /* Text */
  --text-primary:   #111113;
  --text-secondary: #555560;
  --text-muted:     #9898a8;

  /* Borders */
  --border:         #e2e2e8;
  --border-dark:    #c8c8d0;

  /* Footer */
  --footer-bg:      #0f0f11;
  --footer-text:    #9898a8;
  --footer-muted:   #55555f;
  --footer-border:  #1e1e24;

  /* Status colours (small accents only) */
  --green:  #16a34a;
  --amber:  #d97706;
  --red:    #dc2626;

  /* Typography */
  --font-display: 'Syne', sans-serif;
  --font-body:    'Inter', sans-serif;
  --font-mono:    'DM Mono', monospace;

  /* Spacing scale */
  --space-xs:  4px;
  --space-sm:  8px;
  --space-md:  16px;
  --space-lg:  24px;
  --space-xl:  40px;
  --space-2xl: 64px;
  --space-3xl: 96px;

  /* Border radius */
  --radius-sm: 5px;
  --radius-md: 8px;
  --radius-lg: 14px;
  --radius-xl: 20px;

  /* Transition */
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
  --t:    0.18s;
}

/* ------------------------------------------------------------
   RESET
------------------------------------------------------------ */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.7;
  color: var(--text-primary);
  background: var(--bg);
  /* Prevent horizontal scroll on mobile */
  overflow-x: hidden;
}

a {
  color: inherit;
  text-decoration: none;
}

ul, ol { list-style: none; }
img { max-width: 100%; display: block; }
button { cursor: pointer; font-family: inherit; border: none; background: none; }

/* ------------------------------------------------------------
   SCROLLBAR
------------------------------------------------------------ */
::-webkit-scrollbar { width: 5px; height: 5px; }
::-webkit-scrollbar-track { background: var(--bg-off); }
::-webkit-scrollbar-thumb { background: var(--border-dark); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: var(--indigo); }

/* ------------------------------------------------------------
   LAYOUT UTILITIES
------------------------------------------------------------ */
.container {
  width: 100%;
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

/* Section vertical rhythm */
section {
  padding: var(--space-3xl) 0;
}

/* Alternate section background — keeps the page from looking flat */
section.bg-off {
  background: var(--bg-off);
}

/* ------------------------------------------------------------
   TYPOGRAPHY
------------------------------------------------------------ */
h1, h2, h3, h4, h5 {
  font-family: var(--font-display);
  font-weight: 800;
  line-height: 1.15;
  letter-spacing: -0.025em;
  color: var(--text-primary);
}

/* Fluid font sizes: scale between mobile and desktop */
h1 { font-size: clamp(2.4rem, 5.5vw, 4.2rem); }
h2 { font-size: clamp(1.7rem, 3.5vw, 2.5rem); }
h3 { font-size: 1.1rem; font-weight: 700; }
h4 { font-size: 0.95rem; font-weight: 600; letter-spacing: 0; }

p {
  color: var(--text-secondary);
  line-height: 1.75;
}

code {
  font-family: var(--font-mono);
  font-size: 0.85em;
  background: var(--bg-subtle);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 1px 6px;
  color: var(--indigo);
}

/* ------------------------------------------------------------
   SECTION HEADING BLOCK — reused across all sections
   Usage: <div class="section-header"> ... </div>
------------------------------------------------------------ */
.section-header {
  margin-bottom: var(--space-xl);
}

/* Small label above the heading */
.section-label {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--indigo);        /* indigo used sparingly for this label */
  margin-bottom: 12px;
}

.section-label::before {
  content: '';
  display: block;
  width: 16px;
  height: 1px;
  background: var(--indigo);
}

.section-header h2 {
  margin-bottom: 12px;
}

.section-header p {
  max-width: 520px;
  font-size: 1.02rem;
}

/* ------------------------------------------------------------
   BUTTONS
------------------------------------------------------------ */

/* Primary: solid black — clean, confident */
.btn-primary {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 24px;
  background: var(--text-primary);
  color: #fff;
  border-radius: var(--radius-md);
  font-weight: 600;
  font-size: 0.9rem;
  transition: background var(--t) var(--ease), transform var(--t);
}
.btn-primary:hover {
  background: var(--indigo);   /* hover reveals indigo */
  transform: translateY(-1px);
}

/* Secondary: ghost with border */
.btn-secondary {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 24px;
  background: transparent;
  color: var(--text-primary);
  border: 1px solid var(--border-dark);
  border-radius: var(--radius-md);
  font-weight: 500;
  font-size: 0.9rem;
  transition: border-color var(--t), color var(--t), transform var(--t);
}
.btn-secondary:hover {
  border-color: var(--indigo);
  color: var(--indigo);
  transform: translateY(-1px);
}

/* ------------------------------------------------------------
   FEATHER ICON SIZE HELPER
   Feather icons inherit font-size by default; this normalises them.
------------------------------------------------------------ */
[data-feather] {
  width: 18px;
  height: 18px;
  stroke-width: 1.8;
  flex-shrink: 0;
}

/* Icon size variants */
.icon-sm [data-feather], [data-feather].sm { width: 14px; height: 14px; }
.icon-lg [data-feather], [data-feather].lg { width: 22px; height: 22px; }

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

/* Visible focus ring — important for keyboard navigation */
:focus-visible {
  outline: 2px solid var(--indigo);
  outline-offset: 3px;
  border-radius: 3px;
}

/* ------------------------------------------------------------
   BACK TO TOP BUTTON
   Floats in the bottom-right corner; appears after scrolling.
------------------------------------------------------------ */
#back-top {
  position: fixed;
  bottom: 28px;
  right: 28px;
  width: 40px;
  height: 40px;
  background: var(--text-primary);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.3s, transform 0.2s var(--ease), background var(--t);
  z-index: 50;
}
#back-top.visible {
  opacity: 1;
  pointer-events: all;
}
#back-top:hover {
  background: var(--indigo);
  transform: translateY(-2px);
}
#back-top [data-feather] { width: 16px; height: 16px; }

/* ------------------------------------------------------------
   RESPONSIVE HELPERS
------------------------------------------------------------ */
@media (max-width: 640px) {
  section { padding: 64px 0; }
}

@media (min-width: 1400px) {
  .container { max-width: 1260px; }
}