:root {
  --color-ok: #22c55e;
  --color-warn: #f59e0b;
  --color-err: #ef4444;
  --color-bg: #f8fafc;
  --color-card: #ffffff;
  --color-text: #1e293b;
  --color-muted: #64748b;
  --radius: 8px;
  --shadow: 0 1px 3px rgba(0,0,0,.12), 0 1px 2px rgba(0,0,0,.08);
  font-size: 16px;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: system-ui, -apple-system, sans-serif;
  background: var(--color-bg);
  color: var(--color-text);
  min-height: 100vh;
}

/* ── Banner ───────────────────────────────────────────────────────────────── */
.banner {
  padding: .75rem 1.5rem;
  font-size: .875rem;
  font-weight: 600;
  letter-spacing: .02em;
  transition: background .3s;
}
.banner-ok          { background: var(--color-ok);   color: #fff; }
.banner-warn        { background: var(--color-warn);  color: #fff; }
.banner-disconnected{ background: var(--color-err);   color: #fff; }

/* ── Layout ───────────────────────────────────────────────────────────────── */
main {
  max-width: 720px;
  margin: 1.5rem auto;
  padding: 0 1rem;
  display: grid;
  gap: 1rem;
}

.card {
  background: var(--color-card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 1.25rem;
}

.card h2 {
  font-size: .8rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: .08em;
  color: var(--color-muted);
  margin-bottom: .75rem;
}

/* ── Amount display ───────────────────────────────────────────────────────── */
.amount-display {
  font-size: 3rem;
  font-weight: 700;
  text-align: right;
  letter-spacing: .04em;
  margin-bottom: 1rem;
  font-variant-numeric: tabular-nums;
  min-height: 3.5rem;
}

/* ── Keypad ───────────────────────────────────────────────────────────────── */
.keypad {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: .5rem;
}

.key {
  padding: .875rem;
  font-size: 1.25rem;
  font-weight: 600;
  border: 1px solid #e2e8f0;
  border-radius: var(--radius);
  background: #fff;
  cursor: pointer;
  transition: background .1s;
}
.key:hover  { background: #f1f5f9; }
.key:active { background: #e2e8f0; }
.key-clear      { color: var(--color-err); }
.key-backspace  { font-size: 1rem; }

/* ── Button grids ─────────────────────────────────────────────────────────── */
.btn-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
  gap: .5rem;
}

.btn {
  padding: .75rem 1rem;
  border: none;
  border-radius: var(--radius);
  font-size: .875rem;
  font-weight: 600;
  cursor: pointer;
  transition: opacity .15s, filter .15s;
}
.btn:disabled { opacity: .4; cursor: not-allowed; }
.btn:not(:disabled):hover { filter: brightness(1.06); }
.btn:not(:disabled):active { filter: brightness(.94); }

.btn-primary   { background: #3b82f6; color: #fff; }
.btn-secondary { background: #8b5cf6; color: #fff; }
.btn-warn      { background: var(--color-warn); color: #fff; }
.btn-danger    { background: var(--color-err); color: #fff; }
.btn-info      { background: #0ea5e9; color: #fff; }

/* ── Event log ────────────────────────────────────────────────────────────── */
.event-card { max-height: 280px; display: flex; flex-direction: column; }

.reqid {
  font-size: .7rem;
  font-weight: 400;
  color: var(--color-muted);
  font-family: monospace;
  margin-left: .5rem;
}

#event-list {
  list-style: none;
  overflow-y: auto;
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: .35rem;
}

#event-list li {
  font-size: .875rem;
  padding: .35rem .5rem;
  border-radius: 4px;
  background: #f1f5f9;
  font-family: monospace;
}

#event-list li.event-result-ok   { background: #dcfce7; }
#event-list li.event-result-fail  { background: #fee2e2; }

/* ── Receipt ──────────────────────────────────────────────────────────────── */
.receipt-card dl {
  display: grid;
  grid-template-columns: max-content 1fr;
  gap: .25rem .75rem;
  font-size: .875rem;
}
.receipt-card dt {
  color: var(--color-muted);
  font-weight: 600;
}
.receipt-card dd {
  font-family: monospace;
  word-break: break-all;
}