/* ==========================================================================
   StudySpace — reset, base elements and layout primitives
   ========================================================================== */

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--topbar-h) + 16px);
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
  }
}

body {
  margin: 0;
  background: var(--canvas);
  color: var(--text);
  font-family: var(--font-sans);
  font-size: var(--text-base);
  line-height: var(--leading-normal);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
}

body.is-locked { overflow: hidden; }

h1, h2, h3, h4, h5 {
  font-family: var(--font-display);
  color: var(--text-strong);
  line-height: var(--leading-tight);
  letter-spacing: var(--tracking-tight);
  margin: 0;
  font-weight: 700;
}

p { margin: 0; }
ul, ol { margin: 0; padding: 0; list-style: none; }
img, svg, video { display: block; max-width: 100%; }
button, input, select, textarea { font: inherit; color: inherit; }
button { background: none; border: 0; padding: 0; cursor: pointer; }
a { color: inherit; text-decoration: none; }
hr { border: 0; border-top: 1px solid var(--border); margin: 0; }
table { border-collapse: collapse; width: 100%; }

/* Visible, high-contrast focus for every interactive element (WCAG 2.2:
   2.4.11 focus not obscured, 2.4.13 perimeter + 3:1 contrast). */
:where(a, button, input, select, textarea, summary, [tabindex]):focus-visible {
  outline: 3px solid var(--violet-400);
  outline-offset: 2px;
  border-radius: var(--r-xs);
}

.site-header :where(a, button, input, [tabindex]):focus-visible,
.site-footer :where(a, button, input, [tabindex]):focus-visible {
  outline-color: var(--amber-400);
}

::selection { background: var(--violet-600); color: var(--text-invert); }

/* Scrollbars — subtle, not hidden (hidden scrollbars hurt a11y). */
* { scrollbar-width: thin; scrollbar-color: var(--slate-300) transparent; }
*::-webkit-scrollbar { width: 10px; height: 10px; }
*::-webkit-scrollbar-thumb {
  background: var(--slate-300);
  border-radius: var(--r-pill);
  border: 3px solid transparent;
  background-clip: content-box;
}
*::-webkit-scrollbar-track { background: transparent; }

/* ---- Skip link ------------------------------------------------------- */
.skip-link {
  position: fixed;
  top: -100px;
  left: 16px;
  z-index: 200;
  padding: 12px 20px;
  background: var(--violet-600);
  color: var(--text-invert);
  border-radius: var(--r-md);
  font-weight: 700;
  transition: top var(--dur) var(--ease);
}
.skip-link:focus { top: 12px; }

/* ---- Layout ---------------------------------------------------------- */
.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--sp-6);
}
.container-wide {
  width: 100%;
  max-width: var(--container-wide);
  margin-inline: auto;
  padding-inline: var(--sp-6);
}
.container-narrow {
  width: 100%;
  max-width: 860px;
  margin-inline: auto;
  padding-inline: var(--sp-6);
}

.section { padding-block: var(--sp-10); }
.section-tight { padding-block: var(--sp-9); }
.stack { display: grid; gap: var(--sp-4); }
.row { display: flex; align-items: center; gap: var(--sp-3); }
.row-between { display: flex; align-items: center; justify-content: space-between; gap: var(--sp-4); }
.wrap { flex-wrap: wrap; }
.center { text-align: center; }

.grid { display: grid; gap: var(--sp-5); }

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

/* ---- Typographic helpers --------------------------------------------- */
.eyebrow {
  font-size: var(--text-2xs);
  font-weight: 800;
  letter-spacing: var(--tracking-wide);
  text-transform: uppercase;
  color: var(--violet-600);
  margin: 0 0 var(--sp-2);
}
.site-header .eyebrow, .site-footer .eyebrow, .auth-brand .eyebrow { color: var(--amber-400); }

.section-title {
  font-size: clamp(1.45rem, 1.2rem + 1vw, var(--text-2xl));
  font-weight: 600;
}
.muted { color: var(--text-muted); }
.subtle { color: var(--text-subtle); }
.tiny { font-size: var(--text-xs); }
.small { font-size: var(--text-sm); }
.strong { font-weight: 700; color: var(--text-strong); }
.truncate { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }

/* ---- Responsive ------------------------------------------------------ */
@media (max-width: 760px) {
  .container, .container-wide, .container-narrow { padding-inline: var(--sp-4); }
  .section { padding-block: var(--sp-8); }
  body { padding-bottom: var(--tabbar-h); }
}

/* Shown only when JavaScript is disabled */
.noscript-bar {
  background: var(--amber-100);
  color: var(--amber-900);
  border-bottom: 1px solid var(--amber-400);
  padding: 10px 16px;
  font-size: 13px;
  text-align: center;
}
.noscript-bar a { text-decoration: underline; }

/* The `hidden` attribute must win over component display rules. */
[hidden] { display: none !important; }