/* ── Reset and page frame ─────────────────────────────────────────────────
 *
 * Small on purpose. Everything below either removes a default that fights a
 * phone, or sets something every screen depends on.
 * ─────────────────────────────────────────────────────────────────────── */

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

html {
  -webkit-text-size-adjust: 100%;
  /* The page never scrolls sideways. Anything wide gets its own scroller. */
  overflow-x: hidden;
}

body {
  margin: 0;
  min-height: 100dvh;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--ui);
  font-size: var(--t-4);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  /* Stops a rubber-band scroll from dragging the whole app on iOS. */
  overscroll-behavior-y: none;
}

h1, h2, h3, p, figure, ul, ol, dl, dd { margin: 0; }
ul, ol { padding: 0; list-style: none; }

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

button {
  background: none;
  border: 0;
  padding: 0;
  cursor: pointer;
  /* iOS otherwise waits 300ms and then fires a synthetic click. */
  touch-action: manipulation;
  -webkit-tap-highlight-color: transparent;
}

svg { display: block; }
a { color: inherit; }

/* Every digit that lines up in a column, lines up. */
.num, .prob, .board__cell, .trow, table { font-variant-numeric: tabular-nums; }

/* Keyboard focus is always visible, and never only on :focus — that would
   also ring a control somebody merely tapped. */
:focus-visible {
  outline: 2px solid var(--brand);
  outline-offset: 2px;
  border-radius: var(--r-sm);
}

::selection { background: var(--alive-wash); }

/**
 * Motion is a nicety and some people get sick from it. Everything below is
 * transition and transform only, so removing it costs nothing structural.
 */
@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;
  }
}

/* Visible to a screen reader, invisible to everyone else. */
.sr {
  position: absolute;
  width: 1px; height: 1px;
  margin: -1px; padding: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

.noscript {
  max-width: 34rem;
  margin: 18vh auto;
  padding: var(--s-5);
  font-family: var(--ui);
}