/* ============================================================
   FOUNDATION.CSS — Design Tokens & Base Styles
   Resistor Technology · resistor.technology
   ============================================================ */

/* --- Google Fonts --- */
@import url('https://fonts.googleapis.com/css2?family=Space+Grotesk:wght@400;500;600;700&family=Inter:wght@400;500;600&family=IBM+Plex+Mono:wght@400;500&display=swap');

/* --- Design Tokens --- */
:root {
  /* Color Palette: "Bunker + Brass" */
  --color-bg:              #0a0a0c;
  --color-surface:         #14141a;
  --color-surface-raised:  #1e1e24;
  --color-border:          #2a2a30;
  --color-border-light:    #3a3a40;

  --color-text-primary:    #d8d5cd;
  --color-text-secondary:  #9a9a9e;
  --color-text-muted:      #6a6a70;

  --color-brass:           #c4a67a;
  --color-brass-light:     #d4be88;
  --color-brass-dark:      #a08050;
  --color-amethyst:        #6a4a8a;
  --color-amethyst-light:  #a080c0;
  --color-amethyst-dark:   #4a2a6a;
  --color-teal:            #4a8a7a;
  --color-teal-light:      #6aaa9a;
  --color-teal-dark:       #2a6a5a;

  --color-white:           #ffffff;
  --color-black:           #000000;

  /* Typography */
  --font-display:  'Space Grotesk', sans-serif;
  --font-body:     'Inter', sans-serif;
  --font-mono:     'IBM Plex Mono', monospace;

  --fs-hero:       clamp(2.5rem, 5vw, 4.5rem);
  --fs-h1:         clamp(2rem, 4vw, 3.5rem);
  --fs-h2:         clamp(1.5rem, 3vw, 2.5rem);
  --fs-h3:         clamp(1.125rem, 2vw, 1.5rem);
  --fs-body:       1rem;
  --fs-small:      0.875rem;
  --fs-xs:         0.75rem;

  --lh-tight:      1.2;
  --lh-normal:     1.6;
  --lh-loose:      1.8;

  --ls-wide:       0.15em;
  --ls-wider:      0.25em;

  /* Spacing */
  --space-xs:      0.25rem;
  --space-sm:      0.5rem;
  --space-md:      1rem;
  --space-lg:      2rem;
  --space-xl:      4rem;
  --space-2xl:     6rem;
  --space-3xl:     8rem;

  /* Layout */
  --max-width:     1200px;
  --nav-height:    64px;

  /* Borders */
  --radius-sm:     4px;
  --radius-md:     8px;
  --radius-lg:     12px;
  --radius-full:   9999px;

  /* Transitions */
  --ease-out:      cubic-bezier(0.16, 1, 0.3, 1);
  --ease-in-out:   cubic-bezier(0.65, 0, 0.35, 1);
  --duration-fast: 150ms;
  --duration-med:  300ms;
  --duration-slow: 600ms;

  /* Interactive controls (set by JS) */
  --grain-opacity:    0.04;
  --glow-intensity:   0.5;
  --parallax-depth:   0.5;
  --color-invert:     0;
}

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

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-body);
  font-size: var(--fs-body);
  line-height: var(--lh-normal);
  color: var(--color-text-primary);
  background-color: var(--color-bg);
  overflow-x: hidden;
}

/* --- Typography Base --- */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-display);
  font-weight: 600;
  line-height: var(--lh-tight);
}

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

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

ul, ol {
  list-style: none;
}

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

/* --- Film Grain Overlay --- */
.grain-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  z-index: 9999;
  opacity: var(--grain-opacity);
  mix-blend-mode: overlay;
}

.grain-overlay svg {
  width: 100%;
  height: 100%;
}

/* --- Color Inversion Overlay (controlled by GLOW knob) --- */
.invert-overlay {
  position: fixed;
  inset: 0;
  z-index: 10000;
  pointer-events: none;
  mix-blend-mode: difference;
  background: white;
  opacity: var(--color-invert);
}

/* --- Skip to Content (A11y) --- */
.skip-link {
  position: absolute;
  top: -100%;
  left: 50%;
  transform: translateX(-50%);
  background: var(--color-brass);
  color: var(--color-bg);
  padding: var(--space-sm) var(--space-md);
  font-family: var(--font-mono);
  font-size: var(--fs-small);
  border-radius: var(--radius-sm);
  z-index: 10001;
  transition: top var(--duration-fast);
}

.skip-link:focus {
  top: var(--space-md);
}

/* --- Selection --- */
::selection {
  background: var(--color-brass);
  color: var(--color-bg);
}

/* --- Focus Visible --- */
:focus-visible {
  outline: 2px solid var(--color-brass);
  outline-offset: 2px;
}

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

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

::-webkit-scrollbar-thumb {
  background: var(--color-border);
  border-radius: var(--radius-full);
}

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

/* --- Reduced Motion --- */
@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;
  }

  .grain-overlay {
    display: none;
  }

  .invert-overlay {
    display: none;
  }
}