/* ==========================================================================
   Base: reset, document defaults, typography primitives
   ========================================================================== */

*,
*::before,
*::after {
  box-sizing: border-box;
}

* {
  margin: 0;
}

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  /* Anchor links land below the fixed nav rather than under it. */
  scroll-padding-top: calc(var(--nav-height) + var(--space-6));
}

body {
  font-family: var(--font-sans);
  font-size: var(--text-md);
  line-height: var(--leading-relaxed);
  font-weight: var(--weight-regular);
  color: var(--color-text);
  background-color: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
  min-height: 100vh;
  /* Theme swaps shouldn't snap. */
  transition: background-color var(--duration-base) var(--ease-out),
    color var(--duration-base) var(--ease-out);
}

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

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

button {
  background: none;
  border: none;
  cursor: pointer;
}

/* ---- Headings ------------------------------------------------------------ */

h1,
h2,
h3,
h4,
h5,
h6 {
  font-weight: var(--weight-semibold);
  line-height: var(--leading-tight);
  letter-spacing: var(--tracking-tight);
  color: var(--color-text);
  text-wrap: balance;
}

h1 {
  font-size: var(--text-5xl);
  font-weight: var(--weight-bold);
}

h2 {
  font-size: var(--text-4xl);
}

h3 {
  font-size: var(--text-2xl);
  letter-spacing: var(--tracking-snug);
}

h4 {
  font-size: var(--text-xl);
  letter-spacing: var(--tracking-snug);
  line-height: var(--leading-snug);
}

h5 {
  font-size: var(--text-lg);
  line-height: var(--leading-snug);
  letter-spacing: var(--tracking-normal);
}

h6 {
  font-size: var(--text-base);
  line-height: var(--leading-snug);
  letter-spacing: var(--tracking-normal);
}

/* ---- Text ---------------------------------------------------------------- */

p {
  text-wrap: pretty;
}

a {
  color: var(--color-accent-text);
  text-decoration: none;
  transition: color var(--duration-fast) var(--ease-out);
}

a:hover {
  color: var(--color-accent-hover);
}

strong,
b {
  font-weight: var(--weight-semibold);
}

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

code {
  background-color: var(--color-bg-muted);
  border-radius: var(--radius-sm);
  padding: 0.15em 0.4em;
}

ul,
ol {
  padding-left: var(--space-5);
}

hr {
  border: none;
  border-top: 1px solid var(--color-border);
  margin: 0;
}

/* ---- Focus --------------------------------------------------------------- */

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

:focus:not(:focus-visible) {
  outline: none;
}

/* ---- Selection ----------------------------------------------------------- */

::selection {
  background-color: var(--color-accent-soft);
  color: var(--color-text);
}

/* ---- Accessibility helpers ----------------------------------------------- */

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

.skip-link {
  position: absolute;
  top: var(--space-2);
  left: var(--space-2);
  z-index: 100;
  padding: var(--space-3) var(--space-5);
  background-color: var(--color-surface);
  color: var(--color-text);
  border: 1px solid var(--color-border-strong);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-md);
  font-size: var(--text-sm);
  font-weight: var(--weight-medium);
  transform: translateY(-200%);
  transition: transform var(--duration-fast) var(--ease-out);
}

.skip-link:focus {
  transform: translateY(0);
}

/* ---- Reduced motion ------------------------------------------------------ */

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}