/**
 * base.css: reset + element defaults + page atmosphere.
 * Layers (declared in tokens.css): reset, base, components, utilities, pages.
 */

/* Metric-matched fallback for Inter so the swap from the system font to Inter causes (almost) no layout shift. */
@font-face {
  font-family: "Inter Fallback";
  src: local("Arial"), local("Helvetica Neue"), local("Helvetica");
  size-adjust: 107.12%;
  ascent-override: 90.49%;
  descent-override: 22.56%;
  line-gap-override: 0%;
}

/* ------------------------------------------------------------------ reset */
@layer reset {
  *,
  *::before,
  *::after {
    box-sizing: border-box;
  }

  * {
    margin: 0;
  }

  html {
    -webkit-text-size-adjust: 100%;
    text-size-adjust: 100%;
    tab-size: 4;
  }

  body {
    min-height: 100vh;
    min-height: 100dvh;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    text-rendering: optimizeLegibility;
  }

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

  img,
  video {
    height: auto;
  }

  input,
  button,
  textarea,
  select {
    font: inherit;
    color: inherit;
    letter-spacing: inherit;
  }

  button {
    cursor: pointer;
  }

  button:disabled {
    cursor: not-allowed;
  }

  p,
  h1,
  h2,
  h3,
  h4,
  h5,
  h6 {
    overflow-wrap: break-word;
  }

  ul[role="list"],
  ol[role="list"] {
    list-style: none;
    padding: 0;
  }

  table {
    border-collapse: collapse;
    border-spacing: 0;
  }

  [hidden] {
    display: none !important;
  }

  /* <dialog> defaults we never want */
  dialog {
    color: inherit;
    max-width: none;
    max-height: none;
  }
}

/* ------------------------------------------------------------------- base */
@layer base {
  html {
    background: var(--bg);
    scroll-padding-top: calc(var(--header-h) + 1.25rem);
    scrollbar-color: var(--scrollbar-thumb) transparent;
    scrollbar-width: thin;
  }

  @media (prefers-reduced-motion: no-preference) {
    html {
      scroll-behavior: smooth;
    }
  }

  body {
    position: relative;
    background: var(--bg);
    color: var(--text);
    font-family: var(--font-sans);
    font-size: var(--fs-base);
    line-height: var(--lh-base);
    overflow-x: clip; /* safety net; layouts must not rely on it */
  }

  html.nav-open body {
    overflow: hidden;
  }

  /* Page atmosphere: gradient mesh (::before) + faint grid & grain (::after), fixed, CSS only. */
  body::before,
  body::after {
    content: "";
    position: fixed;
    inset: 0;
    z-index: -1;
    pointer-events: none;
  }

  body::before {
    background:
      radial-gradient(60rem 42rem at 88% -12%, var(--mesh-a), transparent 62%),
      radial-gradient(50rem 40rem at -12% 18%, var(--mesh-b), transparent 62%),
      radial-gradient(46rem 36rem at 62% 112%, var(--mesh-c), transparent 62%);
  }

  body::after {
    background-image:
      var(--noise-img),
      linear-gradient(var(--grid-line) 1px, transparent 1px),
      linear-gradient(90deg, var(--grid-line) 1px, transparent 1px);
    background-size:
      160px 160px,
      72px 72px,
      72px 72px;
    -webkit-mask-image: radial-gradient(120% 90% at 50% 0%, #000 0%, rgba(0, 0, 0, 0.55) 45%, transparent 85%);
    mask-image: radial-gradient(120% 90% at 50% 0%, #000 0%, rgba(0, 0, 0, 0.55) 45%, transparent 85%);
  }

  /* Headings */
  h1,
  h2,
  h3,
  h4 {
    font-family: var(--font-display);
    font-weight: 600;
    line-height: var(--lh-tight);
    letter-spacing: var(--tracking-tight);
    color: var(--text);
    text-wrap: balance;
  }

  h1 {
    font-size: var(--fs-4xl);
  }
  h2 {
    font-size: var(--fs-3xl);
  }
  h3 {
    font-size: var(--fs-xl);
    line-height: var(--lh-snug);
    letter-spacing: -0.02em;
  }
  h4 {
    font-size: var(--fs-lg);
    line-height: var(--lh-snug);
    letter-spacing: -0.01em;
  }

  p {
    text-wrap: pretty;
  }

  a {
    color: var(--accent);
    text-decoration-thickness: 1px;
    text-underline-offset: 0.2em;
    transition: color var(--dur-fast) ease, text-decoration-color var(--dur-fast) ease;
  }

  strong,
  b {
    font-weight: 600;
  }

  small {
    font-size: var(--fs-sm);
  }

  code,
  kbd,
  samp,
  pre {
    font-family: var(--font-mono);
    font-size: 0.92em;
  }

  code:not(pre code) {
    padding: 0.12em 0.4em;
    border-radius: 6px;
    background: var(--code-bg);
  }

  pre {
    overflow-x: auto;
  }

  hr {
    border: 0;
    height: 1px;
    background: linear-gradient(90deg, transparent, var(--border-strong), transparent);
    margin-block: var(--space-7);
  }

  img {
    /* decorative fade-in once decoded; no layout impact */
    background-color: var(--surface);
  }

  ::selection {
    background: var(--selection-bg);
    color: var(--selection-fg);
  }

  /* Focus: one consistent, always visible ring for keyboard users */
  :focus {
    outline: none;
  }

  :focus-visible {
    outline: 2px solid var(--focus-ring);
    outline-offset: 3px;
    border-radius: var(--radius-sm);
  }

  main:focus {
    outline: none;
  }

  /* Scrollbars (WebKit/Blink; Firefox uses scrollbar-color above) */
  ::-webkit-scrollbar {
    width: 10px;
    height: 10px;
  }
  ::-webkit-scrollbar-track {
    background: transparent;
  }
  ::-webkit-scrollbar-thumb {
    background: var(--scrollbar-thumb);
    border-radius: 99px;
    border: 3px solid transparent;
    background-clip: content-box;
  }
  ::-webkit-scrollbar-thumb:hover {
    background: var(--border-strong);
    background-clip: content-box;
  }

  /* Skip link */
  .skip-link {
    position: fixed;
    inset-block-start: 0.75rem;
    inset-inline-start: 0.75rem;
    z-index: calc(var(--z-toast) + 1);
    padding: 0.7rem 1.1rem;
    border-radius: var(--radius-pill);
    background: var(--grad-accent);
    color: var(--accent-contrast);
    font-weight: 600;
    text-decoration: none;
    transform: translateY(-200%);
    transition: transform var(--dur-base) var(--ease-out);
  }

  .skip-link:focus-visible {
    transform: none;
    outline-offset: 2px;
  }

  /* Cross-document view transitions (progressive enhancement) */
  @media (prefers-reduced-motion: no-preference) {
    ::view-transition-old(root) {
      animation: vt-out 220ms var(--ease-out) both;
    }

    ::view-transition-new(root) {
      animation: vt-in 420ms var(--ease-out) 60ms both;
    }

    ::view-transition-group(site-header) {
      animation-duration: 0s;
    }
  }

  @keyframes vt-out {
    to {
      opacity: 0;
      transform: translateY(-6px);
    }
  }

  @keyframes vt-in {
    from {
      opacity: 0;
      transform: translateY(10px);
    }
  }

  /* Reduced motion: no animation, no smooth scrolling, no parallax; final states shown immediately */
  @media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
      animation-duration: 0.01ms !important;
      animation-iteration-count: 1 !important;
      animation-delay: 0ms !important;
      transition-duration: 0.01ms !important;
      transition-delay: 0ms !important;
      scroll-behavior: auto !important;
    }
  }
}

/* Opt every same-origin navigation into a cross-document view transition.
   Unsupporting browsers drop the unknown at-rule; reduced-motion users never get it. */
@media (prefers-reduced-motion: no-preference) {
  @view-transition {
    navigation: auto;
  }
}