/* ===========================================================
   Code Olympiad 2081 - Shared page shell (iOS HIG)
   Reusable chrome for every content sub-page:
   nav bar, segmented control, search, cards, bottom sheet,
   buttons, dev footer, scroll progress. Token-driven only.
   =========================================================== */

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

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

body {
  margin: 0;
  min-height: 100svh;
  background-color: var(--color-canvas);
  color: var(--color-text-primary);
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
}

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

a {
  color: var(--color-accent-strong);
  text-decoration: none;
}

button {
  font: inherit;
  color: inherit;
}

h1,
h2,
h3,
h4 {
  font-family: var(--font-display);
  line-height: 1.15;
  margin: 0;
  letter-spacing: -0.02em;
}

p {
  margin: 0;
}

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

/* Grain overlay for material depth */
body::after {
  content: "";
  position: fixed;
  inset: 0;
  z-index: 1;
  pointer-events: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='140' height='140'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.8' numOctaves='3'/%3E%3C/filter%3E%3Crect width='140' height='140' filter='url(%23n)' opacity='0.5'/%3E%3C/svg%3E");
  opacity: 0.5;
  mix-blend-mode: overlay;
}

/* ---------- Shell ---------- */
.shell {
  width: 100%;
  max-width: var(--shell-width);
  margin-inline: auto;
  padding-inline: clamp(var(--space-md), 4vw, var(--space-2xl));
}

/* ---------- Scroll progress ---------- */
.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  height: 3px;
  width: 100%;
  transform: scaleX(0);
  transform-origin: 0 50%;
  background: linear-gradient(90deg, var(--color-accent), var(--color-accent-strong));
  z-index: 1000;
  transition: transform var(--motion-instant) linear;
}

/* ---------- Nav bar ---------- */
.nav {
  position: sticky;
  top: 0;
  z-index: 900;
  background: var(--color-nav-material);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  border-bottom: 1px solid var(--color-border-hairline);
}

.nav__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-md);
  min-height: var(--nav-height);
  padding-block: var(--space-xs);
}

.nav__brand {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  color: var(--color-text-primary);
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1.0625rem;
  letter-spacing: -0.01em;
}

.nav__brand img {
  width: 34px;
  height: 34px;
  border-radius: var(--radius-full);
  border: 1px solid var(--color-border-hairline);
}

.nav__brand span {
  display: none;
}

@media (min-width: 560px) {
  .nav__brand span {
    display: inline;
  }
}

.nav__actions {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xs);
}

/* ---------- Icon button ---------- */
.icon-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  padding: 0;
  border: 1px solid var(--color-border-hairline);
  border-radius: var(--radius-full);
  background: var(--color-surface-2);
  color: var(--color-text-primary);
  cursor: pointer;
  transition: transform var(--motion-instant) var(--ease-touch),
    background-color var(--motion-instant) var(--ease-touch),
    border-color var(--motion-instant) var(--ease-touch);
}

.icon-btn svg {
  width: var(--icon-md);
  height: var(--icon-md);
}

.icon-btn:hover {
  background: var(--color-surface-hover);
  border-color: var(--color-border-strong);
}

.icon-btn:active {
  transform: scale(0.94);
}

/* ---------- Button ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-xs);
  min-height: 44px;
  padding: 0 var(--space-lg);
  border: 1px solid transparent;
  border-radius: var(--radius-full);
  font-family: var(--font-display);
  font-size: 0.9375rem;
  font-weight: 600;
  cursor: pointer;
  transition: transform var(--motion-instant) var(--ease-touch),
    background-color var(--motion-instant) var(--ease-touch),
    border-color var(--motion-instant) var(--ease-touch),
    box-shadow var(--motion-base) var(--ease-touch);
}

.btn svg {
  width: var(--icon-sm);
  height: var(--icon-sm);
}

.btn:active {
  transform: scale(0.97);
}

.btn--primary {
  background: var(--color-accent);
  color: var(--color-text-on-accent);
}

.btn--primary:hover {
  background: var(--color-accent-strong);
  box-shadow: var(--shadow-card);
}

.btn--ghost {
  background: var(--color-surface-2);
  border-color: var(--color-border-hairline);
  color: var(--color-text-primary);
}

.btn--ghost:hover {
  background: var(--color-surface-hover);
  border-color: var(--color-border-strong);
}

/* ---------- Segmented control ---------- */
.segmented {
  position: relative;
  display: inline-flex;
  padding: var(--space-2xs);
  gap: var(--space-2xs);
  background: var(--color-fill);
  border-radius: var(--radius-full);
  overflow-x: auto;
  scrollbar-width: none;
  max-width: 100%;
}

.segmented::-webkit-scrollbar {
  display: none;
}

.segmented__thumb {
  position: absolute;
  top: var(--space-2xs);
  left: 0;
  height: calc(100% - var(--space-2xs) * 2);
  border-radius: var(--radius-full);
  background: var(--color-surface);
  box-shadow: var(--shadow-card);
  transition: transform var(--motion-base) var(--ease-spring),
    width var(--motion-base) var(--ease-spring);
  will-change: transform, width;
}

.segmented__btn {
  position: relative;
  z-index: 1;
  flex: 0 0 auto;
  min-height: 36px;
  padding: 0 var(--space-md);
  border: none;
  border-radius: var(--radius-full);
  background: transparent;
  color: var(--color-text-secondary);
  font-size: 0.875rem;
  font-weight: 600;
  cursor: pointer;
  transition: color var(--motion-instant) var(--ease-touch);
  white-space: nowrap;
}

.segmented__btn[aria-selected="true"] {
  color: var(--color-text-primary);
}

/* ---------- Search field ---------- */
.search {
  position: relative;
  display: flex;
  align-items: center;
  min-width: 220px;
  flex: 1 1 220px;
  max-width: 340px;
}

.search svg {
  position: absolute;
  left: var(--space-sm);
  width: var(--icon-sm);
  height: var(--icon-sm);
  color: var(--color-text-tertiary);
  pointer-events: none;
}

.search input {
  width: 100%;
  min-height: 44px;
  padding: 0 var(--space-md) 0 calc(var(--space-sm) * 2 + var(--icon-sm));
  border: 1px solid var(--color-border-hairline);
  border-radius: var(--radius-full);
  background: var(--color-surface-2);
  color: var(--color-text-primary);
  font-size: 0.9375rem;
  transition: border-color var(--motion-instant) var(--ease-touch),
    box-shadow var(--motion-instant) var(--ease-touch),
    background-color var(--motion-instant) var(--ease-touch);
}

.search input::placeholder {
  color: var(--color-text-tertiary);
}

.search input:focus {
  outline: none;
  border-color: var(--color-accent);
  background: var(--color-surface);
  box-shadow: 0 0 0 4px var(--color-accent-soft);
}

/* ---------- Toolbar ---------- */
.toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-md);
  flex-wrap: wrap;
  padding-block: var(--space-md);
}

/* ---------- Focus ---------- */
:focus-visible {
  outline: 2px solid var(--color-focus-ring);
  outline-offset: 2px;
  border-radius: var(--radius-xs);
}

/* ---------- Scroll reveal ---------- */
.reveal {
  opacity: 0;
  transform: translateY(18px);
  transition: opacity var(--motion-slow) var(--ease-touch),
    transform var(--motion-slow) var(--ease-spring);
}

.reveal.is-visible {
  opacity: 1;
  transform: none;
}

/* ---------- Bottom sheet ---------- */
.sheet-scrim {
  position: fixed;
  inset: 0;
  z-index: 1100;
  background: var(--color-scrim);
  opacity: 0;
  visibility: hidden;
  transition: opacity var(--motion-base) var(--ease-touch),
    visibility var(--motion-base) var(--ease-touch);
}

.sheet-scrim.is-open {
  opacity: 1;
  visibility: visible;
}

.sheet {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 1150;
  max-height: 88svh;
  overflow-y: auto;
  padding: var(--space-xs) clamp(var(--space-lg), 5vw, var(--space-2xl))
    calc(var(--space-3xl) + env(safe-area-inset-bottom, 0px));
  background: var(--color-surface);
  border-radius: var(--radius-xl) var(--radius-xl) 0 0;
  box-shadow: var(--shadow-sheet);
  transform: translateY(105%);
  transition: transform var(--motion-base) var(--ease-spring);
}

@media (min-width: 720px) {
  .sheet {
    left: 50%;
    right: auto;
    width: min(560px, 92vw);
    transform: translate(-50%, 105%);
    border-radius: var(--radius-xl);
    bottom: var(--space-lg);
  }

  .sheet.is-open {
    transform: translate(-50%, 0);
  }
}

.sheet.is-open {
  transform: translateY(0);
}

.sheet__handle {
  width: 40px;
  height: 5px;
  border-radius: var(--radius-full);
  background: var(--color-border-strong);
  margin: var(--space-xs) auto var(--space-md);
}

.sheet__close {
  position: absolute;
  top: var(--space-md);
  right: var(--space-md);
  width: 36px;
  height: 36px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border: none;
  border-radius: var(--radius-full);
  background: var(--color-fill);
  color: var(--color-text-secondary);
  cursor: pointer;
  transition: background-color var(--motion-instant) var(--ease-touch),
    transform var(--motion-instant) var(--ease-touch);
}

.sheet__close:hover {
  background: var(--color-surface-hover);
}

.sheet__close:active {
  transform: scale(0.94);
}

.sheet__close svg {
  width: var(--icon-sm);
  height: var(--icon-sm);
}

body.no-scroll {
  overflow: hidden;
}

/* ---------- Developer footer ---------- */
.dev-footer {
  margin-top: var(--space-6xl);
  border-top: 1px solid var(--color-border-hairline);
  background: var(--color-surface);
}

.dev-footer__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-2xl);
  padding-block: var(--space-3xl);
}

@media (min-width: 720px) {
  .dev-footer__grid {
    grid-template-columns: 1.4fr 1fr 1fr;
  }
}

.dev-footer h2 {
  font-size: var(--text-kicker);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-accent-strong);
  margin-bottom: var(--space-md);
}

.dev-footer p {
  color: var(--color-text-tertiary);
  font-size: 0.9375rem;
  max-width: 44ch;
}

.dev-footer ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: var(--space-xs);
}

.dev-footer a {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xs);
  color: var(--color-text-secondary);
  font-size: 0.9375rem;
  transition: color var(--motion-instant) var(--ease-touch);
}

.dev-footer a svg {
  width: var(--icon-sm);
  height: var(--icon-sm);
  color: var(--color-text-tertiary);
  transition: color var(--motion-instant) var(--ease-touch);
}

.dev-footer a:hover {
  color: var(--color-accent-strong);
}

.dev-footer a:hover svg {
  color: var(--color-accent-strong);
}

.dev-footer__bottom {
  border-top: 1px solid var(--color-border-hairline);
  padding-block: var(--space-lg);
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-sm);
  color: var(--color-text-tertiary);
  font-size: var(--text-caption);
}

.dev-footer__sign {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xs);
}

.dev-footer__sign img {
  width: 28px;
  height: 28px;
  border-radius: var(--radius-full);
}

/* ---------- Scroll to top ---------- */
.to-top {
  position: fixed;
  right: var(--space-xl);
  bottom: var(--space-xl);
  z-index: 950;
  width: 48px;
  height: 48px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--color-border-strong);
  border-radius: var(--radius-full);
  background: var(--color-surface-2);
  color: var(--color-accent-strong);
  box-shadow: var(--shadow-float);
  cursor: pointer;
  opacity: 0;
  transform: translateY(12px) scale(0.9);
  pointer-events: none;
  transition: opacity var(--motion-base) var(--ease-touch),
    transform var(--motion-base) var(--ease-spring),
    background-color var(--motion-instant) var(--ease-touch),
    border-color var(--motion-instant) var(--ease-touch);
}

.to-top svg {
  width: var(--icon-md);
  height: var(--icon-md);
}

.to-top.is-visible {
  opacity: 1;
  transform: none;
  pointer-events: auto;
}

.to-top:hover {
  background: var(--color-accent);
  border-color: var(--color-accent);
  color: var(--color-text-on-accent);
}

.to-top:active {
  transform: scale(0.94);
}

/* ---------- Utility ---------- */
.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;
}

.is-hidden {
  display: none !important;
}

/* ---------- Reduced motion ---------- */
@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;
  }

  .reveal {
    opacity: 1;
    transform: none;
  }
}