:root {
  color-scheme: light dark;
  --surface:    light-dark(#fcfcfb, #1a1a19);
  --plane:      light-dark(#f4f4f1, #0d0d0d);
  --raised:     light-dark(#ffffff, #232322);
  --ink:        light-dark(#0b0b0b, #ffffff);
  --ink-2:      light-dark(#52514e, #c3c2b7);
  --ink-3:      light-dark(#77756f, #949289);
  --line:       light-dark(rgba(11,11,11,.10), rgba(255,255,255,.11));
  --field:      light-dark(#ffffff, #121211);
  --field-line: light-dark(rgba(11,11,11,.16), rgba(255,255,255,.17));
  --brand:      light-dark(#2a78d6, #3987e5);
  --brand-soft: light-dark(rgba(42,120,214,.12), rgba(57,135,229,.17));
  --good: #0ca30c;
  --bad:  #d03b3b;
  --shadow: light-dark(0 1px 2px rgba(11,11,11,.04) , 0 1px 2px rgba(0,0,0,.5)),
            light-dark(0 14px 40px rgba(11,11,11,.09), 0 14px 40px rgba(0,0,0,.45));
  --r-sm: 11px; --r-lg: 20px;
}
:root[data-theme="light"] { color-scheme: light; }
:root[data-theme="dark"]  { color-scheme: dark; }

*, *::before, *::after { box-sizing: border-box; }
* { -webkit-tap-highlight-color: transparent; }
/* Author display rules beat the UA [hidden] rule, so make it explicit. */
[hidden] { display: none !important; }
@media (prefers-reduced-motion: reduce) { *, *::before, *::after { animation-duration: .01ms !important; transition-duration: .01ms !important; } }

body {
  margin: 0; min-height: 100dvh;
  display: flex; flex-direction: column; align-items: center; justify-content: center;
  padding: max(20px, env(safe-area-inset-top)) 20px max(20px, env(safe-area-inset-bottom));
  background: var(--plane);
  /* Written out per scheme rather than color-mix() over a light-dark()
     variable — nesting those two is not reliably parsed. */
  background-image:
    radial-gradient(60rem 38rem at 50% -12%, light-dark(rgba(42,120,214,.10), rgba(57,135,229,.13)), transparent 70%),
    radial-gradient(40rem 30rem at 92% 112%, rgba(12,163,12,.08), transparent 70%);
  color: var(--ink);
  font: 400 16px/1.55 system-ui, -apple-system, "Segoe UI", sans-serif;
  -webkit-font-smoothing: antialiased;
  accent-color: var(--brand);
}

.themeBtn {
  position: fixed; inset-block-start: max(14px, env(safe-area-inset-top)); inset-inline-end: 14px;
  inline-size: 38px; block-size: 38px; display: grid; place-items: center;
  border: 1px solid var(--line); border-radius: 999px;
  background: var(--raised); color: var(--ink-2); cursor: pointer;
  transition: color .15s, transform .08s;
  &:hover { color: var(--ink); }
  &:active { transform: scale(.94); }
  &:focus-visible { outline: 2px solid var(--brand); outline-offset: 2px; }
}

.shell { inline-size: 100%; max-inline-size: 380px; }

.brand {
  display: grid; justify-items: center; gap: 14px; margin-bottom: 26px; text-align: center;
  & h1 { margin: 0; font-size: 22px; font-weight: 670; letter-spacing: -.02em; }
  & p { margin: 3px 0 0; font-size: 14px; color: var(--ink-3); }
}
.mark {
  position: relative; inline-size: 46px; block-size: 46px; display: grid; place-items: center; color: var(--good);
  & i { position: absolute; inset: 0; border-radius: 50%; border: 2px solid currentColor; opacity: 0; animation: ping 2.8s cubic-bezier(.2,.6,.3,1) infinite; }
  & i:nth-child(2) { animation-delay: .9s; }
  & b { inline-size: 13px; block-size: 13px; border-radius: 50%; background: currentColor; }
}
@keyframes ping { 0% { transform: scale(.32); opacity: .9 } 70% { opacity: 0 } 100% { transform: scale(1); opacity: 0 } }
@media (prefers-reduced-motion: reduce) { .mark i { animation: none; opacity: .35 } }

.card {
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--r-lg); padding: 22px 20px; box-shadow: var(--shadow);
}

label { display: block; font-size: 13px; font-weight: 630; margin-bottom: 7px; color: var(--ink-2); }
.f { position: relative; margin-bottom: 16px; }
input {
  inline-size: 100%; block-size: 48px; padding: 0 14px;
  font: inherit; font-size: 16px;              /* 16px stops iOS zooming on focus */
  color: var(--ink); background: var(--field);
  border: 1px solid var(--field-line); border-radius: var(--r-sm);
  transition: border-color .15s, box-shadow .15s;
  &:focus { outline: none; border-color: var(--brand); box-shadow: 0 0 0 3px var(--brand-soft); }
}
#password { padding-inline-end: 60px; }
.peek {
  position: absolute; inset-inline-end: 5px; inset-block-end: 5px;
  inline-size: 50px; block-size: 38px; display: grid; place-items: center;
  background: none; border: 0; border-radius: 8px; cursor: pointer;
  color: var(--ink-3); font: inherit; font-size: 12.5px; font-weight: 620;
  &:hover { color: var(--ink); }
  &:focus-visible { outline: 2px solid var(--brand); outline-offset: 1px; }
}

.go {
  inline-size: 100%; block-size: 48px; font: inherit; font-weight: 660; font-size: 15px;
  color: #fff; background: var(--brand); border: 0; border-radius: var(--r-sm); cursor: pointer;
  transition: filter .15s, transform .07s;
  &:hover:not(:disabled) { filter: brightness(1.08); }
  &:active:not(:disabled) { transform: translateY(1px); }
  &:disabled { opacity: .62; cursor: progress; }
  &:focus-visible { outline: 2px solid var(--brand); outline-offset: 2px; }
}

.err {
  display: none; align-items: flex-start; gap: 9px;
  background: color-mix(in srgb, var(--bad) 11%, transparent);
  border: 1px solid color-mix(in srgb, var(--bad) 36%, transparent);
  border-radius: var(--r-sm); padding: 11px 12px; font-size: 13.5px; margin-bottom: 16px;
  &.show { display: flex; animation: nudge .3s; }
  & svg { flex: none; margin-block-start: 1px; color: var(--bad); }
}
@keyframes nudge { 25% { translate: -5px } 60% { translate: 4px } 100% { translate: 0 } }

footer { margin-top: 22px; text-align: center; font-size: 12px; color: var(--ink-3); }