:root {
  --bg: #f4f6f8;
  --card: #ffffff;
  --text: #1a1f26;
  --muted: #6b7280;
  --brand: #0f766e;
  --brand-dark: #0b5a54;
  --owe: #dc2626;
  --owed: #16a34a;
  --border: #e5e7eb;
  --danger: #dc2626;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 18px;
  background: var(--brand);
  color: #fff;
  position: sticky;
  top: 0;
  z-index: 10;
}

.topbar .brand {
  font-weight: 700;
  font-size: 1.1rem;
  text-decoration: none;
  color: #fff;
}

.topbar a.home-btn {
  color: #fff;
  text-decoration: none;
  font-size: 0.9rem;
  border: 1px solid rgba(255,255,255,0.5);
  padding: 6px 12px;
  border-radius: 6px;
}

.container {
  max-width: 560px;
  margin: 0 auto;
  padding: 20px 16px 60px;
}

.card {
  background: var(--card);
  border-radius: 12px;
  padding: 18px;
  margin-bottom: 16px;
  box-shadow: 0 1px 3px rgba(0,0,0,0.08);
}

h1 { font-size: 1.6rem; margin: 0 0 8px; }
h2 { font-size: 1.2rem; margin: 0 0 12px; }
p.muted, span.muted { color: var(--muted); font-size: 0.9rem; }

label {
  display: block;
  font-size: 0.85rem;
  color: var(--muted);
  margin: 12px 0 4px;
}

input, select, textarea {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 1rem;
  background: #fff;
  color: var(--text);
}

button, .btn {
  display: inline-block;
  background: var(--brand);
  color: #fff;
  border: none;
  padding: 11px 18px;
  border-radius: 8px;
  font-size: 1rem;
  cursor: pointer;
  text-decoration: none;
  text-align: center;
}

button:hover, .btn:hover { background: var(--brand-dark); }

.btn-secondary {
  background: #fff;
  color: var(--brand);
  border: 1px solid var(--brand);
}

.btn-danger { background: var(--danger); }

.btn-block { width: 100%; margin-top: 14px; }

.row { display: flex; gap: 10px; }
.row > * { flex: 1; }

.error-box {
  display: none;
  background: #fef2f2;
  color: var(--danger);
  border: 1px solid #fecaca;
  padding: 10px 12px;
  border-radius: 8px;
  font-size: 0.9rem;
  margin-top: 12px;
}

.success-box {
  background: #f0fdf4;
  color: var(--owed);
  border: 1px solid #bbf7d0;
  padding: 10px 12px;
  border-radius: 8px;
  font-size: 0.9rem;
  margin-top: 12px;
}

.group-item, .member-row, .expense-row, .balance-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 12px 0;
  border-bottom: 1px solid var(--border);
  text-decoration: none;
  color: var(--text);
}

.group-item:last-child, .member-row:last-child, .expense-row:last-child, .balance-row:last-child {
  border-bottom: none;
}

.amount-owe { color: var(--owe); font-weight: 600; }
.amount-owed { color: var(--owed); font-weight: 600; }
.amount-even { color: var(--muted); }

.support-line {
  text-align: center;
  font-size: 0.85rem;
  color: var(--muted);
  margin-top: 24px;
}

.support-line a { color: var(--brand); text-decoration: none; }

.split-type-tabs {
  display: flex;
  gap: 8px;
  margin: 12px 0;
}

.split-type-tabs button {
  flex: 1;
  background: #fff;
  color: var(--muted);
  border: 1px solid var(--border);
}

.split-type-tabs button.active {
  background: var(--brand);
  color: #fff;
  border-color: var(--brand);
}

.split-member-row {
  display: flex;
  align-items: center;
  gap: 10px;
  margin: 8px 0;
}

.split-member-row label { margin: 0; flex: 1; font-size: 0.95rem; color: var(--text); }
.split-member-row input { width: 110px; flex: none; }

.empty-state {
  text-align: center;
  color: var(--muted);
  padding: 30px 10px;
}

.invite-box {
  background: #f0fdfa;
  border: 1px dashed var(--brand);
  border-radius: 8px;
  padding: 12px;
  text-align: center;
  margin-top: 10px;
}

.invite-code {
  font-size: 1.3rem;
  font-weight: 700;
  letter-spacing: 2px;
  color: var(--brand-dark);
}

.checklist { padding-left: 18px; }
.checklist li { margin-bottom: 8px; }

footer.legal {
  text-align: center;
  font-size: 0.75rem;
  color: var(--muted);
  margin-top: 30px;
}