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

[hidden] { display: none !important; }

:root {
  --primary: #4f46e5;
  --primary-hover: #4338ca;
  --danger: #ef4444;
  --success: #22c55e;
  --warning: #f59e0b;
  --bg: #f8fafc;
  --card-bg: #ffffff;
  --border: #e2e8f0;
  --text: #1e293b;
  --text-muted: #64748b;
  --owe-color: #ef4444;
  --owed-color: #22c55e;
  --radius: 10px;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  font-size: 14px;
  line-height: 1.5;
}

/* ---- SCREENS ---- */
.screen { min-height: 100vh; }

/* ---- LOADING ---- */
.loading-screen {
  display: flex;
  align-items: center;
  justify-content: center;
}

.loading-spinner {
  width: 36px;
  height: 36px;
  border: 3px solid var(--border);
  border-top-color: var(--primary);
  border-radius: 50%;
  animation: spin 0.7s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* ---- AUTH ---- */
#auth-screen {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px;
}

.auth-box {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 40px 36px;
  width: 100%;
  max-width: 400px;
  box-shadow: 0 4px 24px rgba(0,0,0,0.07);
}

.logo {
  font-size: 22px;
  font-weight: 700;
  color: var(--primary);
  margin-bottom: 24px;
  text-align: center;
}

.auth-tabs {
  display: flex;
  gap: 8px;
  margin-bottom: 20px;
}

.tab-btn {
  flex: 1;
  padding: 8px;
  border: 1px solid var(--border);
  background: none;
  border-radius: 6px;
  cursor: pointer;
  color: var(--text-muted);
  font-size: 14px;
  transition: all 0.15s;
}

.tab-btn.active {
  background: var(--primary);
  color: #fff;
  border-color: var(--primary);
}

.auth-form {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.auth-form input {
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 14px;
  outline: none;
  transition: border-color 0.15s;
}

.auth-form input:focus {
  border-color: var(--primary);
}

/* ---- HEADER ---- */
.app-header {
  background: var(--card-bg);
  border-bottom: 1px solid var(--border);
  padding: 0 24px;
  height: 56px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  position: sticky;
  top: 0;
  z-index: 10;
}

.app-header .logo {
  margin: 0;
  font-size: 18px;
}

.header-right {
  display: flex;
  align-items: center;
  gap: 12px;
}

.user-name {
  color: var(--text-muted);
  font-size: 13px;
}

/* ---- MAIN LAYOUT ---- */
.app-main {
  max-width: 800px;
  margin: 0 auto;
  padding: 24px 16px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

/* ---- CARDS ---- */
.card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
}

.card h2 {
  font-size: 16px;
  font-weight: 600;
  margin-bottom: 16px;
}

.section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 16px;
}

.section-header h2 { margin-bottom: 0; }

/* ---- DEBT SUMMARY ---- */
.debt-columns {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
}

.debt-label {
  font-size: 13px;
  font-weight: 600;
  margin-bottom: 8px;
}

.debt-owe-label { color: var(--owe-color); }
.debt-owed-label { color: var(--owed-color); }

.debt-list {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.debt-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 8px 10px;
  border-radius: 6px;
  font-size: 13px;
}

.debt-row.owe {
  background: #fef2f2;
  color: #991b1b;
}

.debt-row.owed {
  background: #f0fdf4;
  color: #166534;
}

.debt-row .debt-amount {
  font-weight: 600;
}

.debt-settled {
  color: var(--text-muted);
  font-size: 13px;
  text-align: center;
  padding: 12px;
}

.loading-text {
  color: var(--text-muted);
  font-size: 13px;
}

/* ---- BUTTONS ---- */
.btn-primary {
  background: var(--primary);
  color: #fff;
  border: none;
  padding: 10px 20px;
  border-radius: 6px;
  cursor: pointer;
  font-size: 14px;
  font-weight: 500;
  transition: background 0.15s;
}

.btn-primary:hover { background: var(--primary-hover); }

.btn-outline {
  background: none;
  color: var(--primary);
  border: 1px solid var(--primary);
  padding: 8px 16px;
  border-radius: 6px;
  cursor: pointer;
  font-size: 14px;
  transition: all 0.15s;
}

.btn-outline:hover {
  background: var(--primary);
  color: #fff;
}

.btn-sm { padding: 5px 10px; font-size: 12px; }

.btn-danger {
  background: none;
  color: var(--danger);
  border: 1px solid var(--danger);
  padding: 4px 10px;
  border-radius: 5px;
  cursor: pointer;
  font-size: 12px;
  transition: all 0.15s;
}

.btn-danger:hover {
  background: var(--danger);
  color: #fff;
}

/* ---- EXPENSE FORM ---- */
#expense-form {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.form-row {
  display: flex;
  gap: 10px;
  align-items: center;
}

.flex-grow { flex: 1; }
.full-width { width: 100%; }

input[type="text"],
input[type="number"],
input[type="date"],
input[type="email"],
select,
textarea {
  padding: 8px 10px;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 14px;
  outline: none;
  transition: border-color 0.15s;
  color: var(--text);
  background: #fff;
}

input:focus, select:focus, textarea:focus {
  border-color: var(--primary);
}

select {
  appearance: none;
  background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' fill='none' viewBox='0 0 20 20'%3e%3cpath stroke='%236b7280' stroke-linecap='round' stroke-linejoin='round' stroke-width='1.5' d='M6 8l4 4 4-4'/%3e%3c/svg%3e");
  background-position: right 8px center;
  background-repeat: no-repeat;
  background-size: 16px;
  padding-right: 28px;
  cursor: pointer;
}

.participants-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.participants-header h3 {
  font-size: 13px;
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.participants-table-wrap {
  overflow-x: auto;
  border: 1px solid var(--border);
  border-radius: 6px;
}

.participants-table {
  width: 100%;
  border-collapse: collapse;
}

.participants-table th {
  padding: 8px 10px;
  text-align: left;
  font-size: 12px;
  font-weight: 600;
  color: var(--text-muted);
  background: #f8fafc;
  border-bottom: 1px solid var(--border);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.participants-table td {
  padding: 6px 8px;
  border-bottom: 1px solid var(--border);
  vertical-align: middle;
}

.participants-table tr:last-child td {
  border-bottom: none;
}

.participants-table select,
.participants-table input[type="number"] {
  padding: 5px 8px;
  font-size: 13px;
  width: 100%;
}

.participants-table select { min-width: 110px; }
.participants-table input[type="number"] { min-width: 70px; }

.share-value-cell { display: flex; align-items: center; gap: 4px; }
.share-value-cell .p-share-currency { min-width: 70px; }

.share-type-btn {
  padding: 4px 10px;
  border-radius: 5px;
  cursor: pointer;
  font-size: 12px;
  font-weight: 500;
  transition: all 0.15s;
  white-space: nowrap;
}

.share-type-btn[data-type="relative"] {
  background: #eff6ff;
  color: #1d4ed8;
  border: 1px solid #bfdbfe;
}

.share-type-btn[data-type="absolute"] {
  background: #f0fdf4;
  color: #15803d;
  border: 1px solid #bbf7d0;
}

.remove-btn {
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 16px;
  padding: 2px 6px;
  border-radius: 4px;
  transition: color 0.15s;
}

.remove-btn:hover { color: var(--danger); }

/* ---- VALIDATION HINTS ---- */
.validation-hints {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
}

.hint {
  font-size: 12px;
  color: var(--text-muted);
  padding: 4px 8px;
  border-radius: 4px;
  background: #f1f5f9;
}

.hint.ok { background: #f0fdf4; color: #166534; }
.hint.err { background: #fef2f2; color: #991b1b; }

.form-actions { display: flex; gap: 10px; }

/* ---- ERROR / SUCCESS ---- */
.error-msg {
  color: var(--danger);
  font-size: 13px;
  min-height: 18px;
}

/* ---- EXPENSE CARDS ---- */
.expense-card {
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 14px 16px;
  margin-bottom: 10px;
  transition: border-color 0.15s;
}

.expense-card:last-child { margin-bottom: 0; }

.expense-card:hover { border-color: #a5b4fc; }

.expense-header {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 8px;
  flex-wrap: wrap;
}

.expense-title {
  font-weight: 600;
  flex: 1;
}

.expense-amount {
  font-weight: 700;
  color: var(--primary);
  font-size: 15px;
}

.expense-currency {
  color: var(--text-muted);
  font-size: 12px;
}

.expense-date {
  color: var(--text-muted);
  font-size: 12px;
}

.expense-meta {
  font-size: 12px;
  color: var(--text-muted);
  margin-bottom: 6px;
}

.expense-participants {
  font-size: 12px;
  color: var(--text-muted);
  margin-bottom: 6px;
}

.expense-note {
  font-size: 12px;
  color: var(--text-muted);
  font-style: italic;
  margin-top: 4px;
}

.expense-footer {
  display: flex;
  justify-content: flex-end;
  margin-top: 8px;
}

.no-expenses {
  text-align: center;
  color: var(--text-muted);
  padding: 32px;
  font-size: 13px;
}

/* ---- RESPONSIVE ---- */
@media (max-width: 600px) {
  .debt-columns { grid-template-columns: 1fr; }
  .form-row { flex-direction: column; align-items: stretch; }
  .app-main { padding: 12px 10px; }
  .card { padding: 16px 14px; }
  .auth-box { padding: 28px 20px; }
}