:root {
  --bg: #f6f6f4;
  --panel: #ffffff;
  --ink: #16181d;
  --muted: #5d6470;
  --line: #d9dbe0;
  --accent: #1f6feb;
  --accent-ink: #ffffff;
  --danger: #b4232b;
  --warn-bg: #fdf6e3;
  --warn-line: #e7d9a8;
  --radius: 10px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #101216;
    --panel: #181b21;
    --ink: #e8eaed;
    --muted: #9aa2af;
    --line: #2b303a;
    --accent: #4c8dff;
    --accent-ink: #0b0d11;
    --danger: #ff7b7b;
    --warn-bg: #1f1c14;
    --warn-line: #3d3523;
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font: 16px/1.55 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  padding: 2rem 1rem 4rem;
}

.wrap { max-width: 640px; margin: 0 auto; }

h1 { font-size: 1.6rem; margin: 0 0 .4rem; letter-spacing: -.02em; }
h2 { font-size: 1rem; margin: 0 0 .5rem; }
.sub { color: var(--muted); margin: 0 0 1.75rem; }

form {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.25rem;
}

label {
  display: block;
  font-size: .8rem;
  font-weight: 600;
  color: var(--muted);
  margin-bottom: .35rem;
  text-transform: uppercase;
  letter-spacing: .04em;
}

input, select {
  width: 100%;
  font: inherit;
  color: var(--ink);
  background: var(--bg);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: .6rem .7rem;
}

input:focus-visible, select:focus-visible, button:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: .75rem;
  margin-top: 1rem;
}

button {
  font: inherit;
  font-weight: 600;
  cursor: pointer;
  border-radius: 8px;
  border: 1px solid var(--line);
  background: var(--panel);
  color: var(--ink);
  padding: .6rem 1rem;
}

button:hover { border-color: var(--accent); }

#go {
  margin-top: 1.1rem;
  width: 100%;
  background: var(--accent);
  color: var(--accent-ink);
  border-color: var(--accent);
  padding: .75rem;
}

.error {
  margin: 1rem 0 0;
  color: var(--danger);
  font-weight: 600;
}

#result { margin-top: 1.75rem; }

.qrbox {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.25rem;
  display: flex;
  justify-content: center;
}

#canvas {
  width: 100%;
  max-width: 320px;
  height: auto;
  image-rendering: pixelated;
}

.encoded {
  margin: 1rem 0 .25rem;
  font-size: .85rem;
  color: var(--muted);
}

.encoded code {
  color: var(--ink);
  word-break: break-all;
  font-size: .85rem;
}

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: .5rem;
  margin-top: .9rem;
}

.actions button { flex: 1 1 140px; }

.hint { font-size: .8rem; color: var(--muted); margin: .75rem 0 0; }

footer {
  margin-top: 2.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--line);
  font-size: .9rem;
  color: var(--muted);
}

footer p { margin: 0 0 .75rem; }

.warn {
  background: var(--warn-bg);
  border: 1px solid var(--warn-line);
  border-radius: 8px;
  padding: .7rem .85rem;
}

[hidden] { display: none !important; }

.bg-field {
  display: flex;
  align-items: center;
  gap: .6rem;
}

.bg-field input[type="color"] {
  flex: 0 0 auto;
  width: 3.4rem;
}

.check {
  display: flex;
  align-items: center;
  gap: .5rem;
  text-transform: none;
  font-weight: 500;
  color: var(--ink);
  font-size: .9rem;
  white-space: nowrap;
  padding: .5rem .2rem;
  cursor: pointer;
}
.check input {
  width: 1.3rem;
  height: 1.3rem;
  margin: 0;
  flex: 0 0 auto;
  accent-color: var(--accent);
}

input[type="color"] {
  padding: .25rem;
  height: 2.4rem;
  cursor: pointer;
}

@media (max-width: 480px) {
  body { padding: 1.5rem .75rem 3rem; }

  .row-colors { grid-template-columns: 1fr 1fr; }

  .bg-field {
    flex-wrap: wrap;
    gap: .4rem .6rem;
  }
  .check { white-space: normal; font-size: .85rem; }
}

.warn-inline {
  margin: .6rem 0 0;
  font-size: .82rem;
  color: var(--danger);
}

.qrbox.checkerboard {
  background-image:
    linear-gradient(45deg, #ccc 25%, transparent 25%),
    linear-gradient(-45deg, #ccc 25%, transparent 25%),
    linear-gradient(45deg, transparent 75%, #ccc 75%),
    linear-gradient(-45deg, transparent 75%, #ccc 75%);
  background-size: 20px 20px;
  background-position: 0 0, 0 10px, 10px -10px, -10px 0;
  background-color: #fff;
}