:root {
  --bg: #f5f6f8;
  --card: #ffffff;
  --ink: #1a1d21;
  --sub: #6b7280;
  --line: #e5e7eb;
  --accent: #2563eb;
  --accent-ink: #ffffff;
  --neg: #dc2626;
  --pos: #16a34a;
  --warn-bg: #fef3c7;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--ink);
  font-size: 16px;
  line-height: 1.45;
}
nav {
  display: flex;
  gap: 0.25rem;
  overflow-x: auto;
  background: var(--card);
  border-bottom: 1px solid var(--line);
  padding: 0.5rem 0.75rem;
  position: sticky;
  top: 0;
}
nav a {
  padding: 0.5rem 0.75rem;
  border-radius: 0.5rem;
  text-decoration: none;
  color: var(--sub);
  white-space: nowrap;
  font-weight: 500;
}
nav a.on { background: var(--accent); color: var(--accent-ink); }
main { max-width: 680px; margin: 0 auto; padding: 1rem; }
h1 { font-size: 1.4rem; margin: 0.5rem 0 1rem; }
h2 { font-size: 1.05rem; margin: 0 0 0.5rem; }
h3 { font-size: 0.9rem; margin: 0.75rem 0 0.25rem; color: var(--sub); }
.sub { color: var(--sub); font-size: 0.85em; font-weight: normal; }
.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 0.75rem;
  padding: 1rem;
  margin-bottom: 1rem;
}
.money { font-variant-numeric: tabular-nums; font-weight: 600; }
.money.neg { color: var(--neg); }
.big { font-size: 1.8rem; margin: 0.25rem 0; }
.balances { display: flex; gap: 2rem; }
.balances .label { display: block; color: var(--sub); font-size: 0.8rem; }
ul.rows { list-style: none; margin: 0; padding: 0; }
ul.rows li {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem 0.75rem;
  align-items: center;
  padding: 0.55rem 0;
  border-bottom: 1px solid var(--line);
}
ul.rows li:last-child { border-bottom: none; }
ul.rows li.overdue { background: var(--warn-bg); border-radius: 0.5rem; padding: 0.55rem; }
.actions { display: flex; gap: 0.5rem; margin-left: auto; }
form.inline { display: flex; flex-wrap: wrap; gap: 0.5rem; align-items: center; }
form.stack { display: flex; flex-direction: column; gap: 0.75rem; }
label { display: flex; flex-direction: column; gap: 0.25rem; font-size: 0.9rem; color: var(--sub); }
label.check { flex-direction: row; align-items: center; gap: 0.5rem; }
input, select, button {
  font: inherit;
  padding: 0.6rem 0.7rem;
  border: 1px solid var(--line);
  border-radius: 0.5rem;
  background: var(--card);
  color: var(--ink);
  min-height: 44px; /* touch target */
}
input[type="checkbox"] { min-height: auto; width: 1.2rem; height: 1.2rem; }
form.inline input[type="text"] { width: 7rem; }
.btn {
  display: inline-block;
  border: 1px solid var(--line);
  background: var(--card);
  color: var(--ink);
  border-radius: 0.5rem;
  padding: 0.6rem 1rem;
  text-decoration: none;
  font-weight: 500;
  cursor: pointer;
  text-align: center;
}
.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.btn.danger { color: var(--neg); border-color: var(--neg); }
.flash {
  background: var(--warn-bg);
  border-radius: 0.5rem;
  padding: 0.6rem 0.8rem;
}
.scroll { overflow-x: auto; }
table { border-collapse: collapse; width: 100%; font-size: 0.9rem; }
th, td { text-align: right; padding: 0.4rem 0.6rem; border-bottom: 1px solid var(--line); }
th:first-child, td:first-child { text-align: left; }
th { color: var(--sub); font-weight: 500; }
a { color: var(--accent); }
h2 a, .rows a { color: inherit; }
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #111418;
    --card: #1b1f26;
    --ink: #e7eaee;
    --sub: #9aa3af;
    --line: #2a2f38;
    --warn-bg: #4a3a10;
  }
}