/* --- Base / tokens ------------------------------------------------------- */
:root {
  --bg: #ffffff;
  --bg-panel: #f7f8fa;
  --text: #131417;
  --muted: #5b616e;
  --border: #d7dbe2;
  --accent: #2563eb;     /* buttons/focus */
  --accent-weak: #e6efff;
  --ok: #0f9d58;
  --ok-bg: #e9f6ef;
  --error: #d93025;
  --error-bg: #fdeaea;
  --shadow: 0 1px 2px rgba(0,0,0,.06), 0 6px 24px rgba(0,0,0,.06);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0c0d10;
    --bg-panel: #15171c;
    --text: #e7e9ee;
    --muted: #a2a9b6;
    --border: #2a2f39;
    --accent: #60a5fa;
    --accent-weak: #102548;
    --ok: #8bd2a8;
    --ok-bg: #0e1b14;
    --error: #ff8a80;
    --error-bg: #2a1412;
    --shadow: none;
  }
}

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

html { font-size: 16px; }
body {
  margin: 0;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, "Helvetica Neue", Arial, "Noto Sans", "Apple Color Emoji", "Segoe UI Emoji";
  color: var(--text);
  background: var(--bg);
  line-height: 1.45;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* --- Page chrome --------------------------------------------------------- */
.page-header, .page-footer {
  padding: 1.25rem 1rem;
  border-bottom: 1px solid var(--border);
}
.page-footer { 
  border-bottom: none; 
  border-top: 1px solid var(--border);
  color: var(--muted);
}
.page-header h1 {
  margin: 0 0 .25rem 0;
  font-size: 1.5rem;
  letter-spacing: .2px;
}
.subtitle {
  margin: 0;
  color: var(--muted);
  font-size: .95rem;
}

.container {
  max-width: 1000px;
  margin: 0 auto;
  padding: 1rem;
  display: grid;
  gap: 1rem;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
}

/* --- Panels -------------------------------------------------------------- */
.panel {
  background: var(--bg-panel);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1rem;
  box-shadow: var(--shadow);
}
.panel h2 {
  margin: 0 0 .75rem 0;
  font-size: 1.25rem;
}

/* --- Forms --------------------------------------------------------------- */
.form { display: grid; gap: .75rem; }

.field { display: grid; gap: .35rem; }

label {
  font-weight: 600;
  font-size: .95rem;
}

input[type="number"],
select,
output,
.out,
button {
  width: 100%;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: #fff0; /* transparent to inherit panel bg in dark mode */
  color: var(--text);
}

input[type="number"],
select {
  padding: .7rem .8rem;
  min-height: 44px;   /* touch target */
}

.help {
  color: var(--muted);
  font-size: .85rem;
}

/* Result box */
.out,
output {
  display: block;
  min-height: 44px;
  padding: .7rem .8rem;
  background: var(--accent-weak);
  border-color: transparent;
  border-radius: 10px;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  word-break: break-word;
}

/* Buttons */
.actions { margin-top: .25rem; }
button {
  background: var(--accent);
  color: white;
  border: none;
  cursor: pointer;
  font-weight: 600;
  letter-spacing: .2px;
  transition: transform .02s ease, filter .15s ease;
}
button:hover { filter: brightness(1.05); }
button:active { transform: translateY(1px); }
button:disabled {
  opacity: .6;
  cursor: not-allowed;
}

/* Focus styles (keyboard-friendly) */
:focus-visible {
  outline: 3px solid color-mix(in oklab, var(--accent) 60%, transparent);
  outline-offset: 2px;
  border-radius: 12px;
}

/* Validation helpers you’ll toggle from JS */
.error {
  border-color: var(--error) !important;
  background: var(--error-bg) !important;
}
.ok {
  border-color: var(--ok) !important;
  background: var(--ok-bg) !important;
}

/* Layout tweaks for the Settings panel you placed after <main> */
#datum-title { margin-top: .25rem; }
#datum {
  max-width: 360px;
}

/* --- Responsive spacing --------------------------------------------------- */
@media (min-width: 900px) {
  .page-header, .page-footer { padding: 1.2rem 0; }
  .container { padding: 1.25rem; gap: 1.25rem; }
  .panel { padding: 1.1rem; }
}

/* --- Motion & print ------------------------------------------------------- */
@media (prefers-reduced-motion: reduce) {
  * { transition: none !important; animation: none !important; }
}

@media print {
  .page-header, .page-footer { display: none; }
  .panel { box-shadow: none; background: #fff; }
}