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

:root {
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --red: #dc2626;
    --red-bg: #fef2f2;
    --green: #16a34a;
    --green-bg: #f0fdf4;
    --amber: #d97706;
    --amber-bg: #fffbeb;
    --gray-bg: #f4f5f7;
    --border: #e5e7eb;
    --text: #111827;
    --text-muted: #6b7280;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
    background: var(--gray-bg);
    color: var(--text);
    min-height: 100vh;
    padding-bottom: 40px;
}

/* --- Navbar --- */
.navbar {
    background: #fff;
    border-bottom: 1px solid var(--border);
    padding: 14px 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: sticky;
    top: 0;
    z-index: 10;
}
.nav-brand { font-weight: 700; font-size: 18px; color: var(--text); text-decoration: none; }
.nav-logout { color: var(--text-muted); text-decoration: none; font-size: 14px; }
.nav-logout:hover { color: var(--red); }

/* --- Container --- */
.container { max-width: 900px; margin: 0 auto; padding: 20px; }
.container-narrow { max-width: 560px; }

/* --- Login --- */
.login-body { display: flex; align-items: center; justify-content: center; min-height: 100vh; }
.login-box {
    background: #fff;
    padding: 40px 32px;
    border-radius: 16px;
    box-shadow: 0 4px 24px rgba(0,0,0,0.08);
    text-align: center;
    width: 90%;
    max-width: 360px;
}
.login-icon { font-size: 40px; margin-bottom: 8px; }
.login-box h1 { font-size: 22px; margin-bottom: 4px; }
.subtitle { color: var(--text-muted); font-size: 14px; margin-bottom: 24px; }
.login-box form { display: flex; flex-direction: column; gap: 12px; }
.login-box input {
    padding: 12px 14px;
    border: 1px solid var(--border);
    border-radius: 10px;
    font-size: 15px;
    text-align: center;
}

/* --- Buttons --- */
.btn {
    display: inline-block;
    padding: 10px 18px;
    border-radius: 10px;
    border: none;
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    text-decoration: none;
    text-align: center;
    transition: background 0.15s;
}
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-dark); }
.btn-secondary { background: #fff; color: var(--text); border: 1px solid var(--border); }
.btn-secondary:hover { background: var(--gray-bg); }
.btn-danger { background: var(--red-bg); color: var(--red); border: 1px solid #fecaca; }
.btn-danger:hover { background: #fee2e2; }
.btn-full { width: 100%; padding: 13px; font-size: 15px; }

/* --- Stats --- */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 12px;
    margin-bottom: 20px;
}
.stat-card {
    background: #fff;
    border-radius: 14px;
    padding: 16px;
    border: 1px solid var(--border);
}
.stat-label { font-size: 13px; color: var(--text-muted); margin-bottom: 6px; }
.stat-value { font-size: 20px; font-weight: 700; }
.stat-sub { font-size: 12px; color: var(--text-muted); margin-top: 2px; }
.stat-overdue .stat-value { color: var(--red); }
.stat-total .stat-value { color: var(--primary); }

/* --- Toolbar --- */
.toolbar { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; margin-bottom: 16px; }
.search-form { display: flex; gap: 6px; flex: 1; min-width: 180px; }
.search-form input {
    flex: 1;
    padding: 9px 12px;
    border: 1px solid var(--border);
    border-radius: 10px;
    font-size: 14px;
}
.search-form button {
    padding: 9px 14px;
    border: 1px solid var(--border);
    background: #fff;
    border-radius: 10px;
    cursor: pointer;
}
.filter-tabs { display: flex; gap: 6px; flex-wrap: wrap; }
.tab {
    padding: 8px 14px;
    border-radius: 20px;
    background: #fff;
    border: 1px solid var(--border);
    color: var(--text-muted);
    text-decoration: none;
    font-size: 13px;
    font-weight: 600;
    white-space: nowrap;
}
.tab.active { background: var(--primary); color: #fff; border-color: var(--primary); }
.btn-add { margin-left: auto; white-space: nowrap; }

/* --- Debt list --- */
.debt-list { display: flex; flex-direction: column; gap: 10px; }
.debt-card {
    background: #fff;
    border-radius: 14px;
    padding: 16px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border: 1px solid var(--border);
    border-left: 4px solid var(--border);
    text-decoration: none;
    color: var(--text);
    gap: 12px;
}
.debt-card.status-overdue { border-left-color: var(--red); }
.debt-card.status-partial { border-left-color: var(--amber); }
.debt-card.status-paid { border-left-color: var(--green); opacity: 0.7; }
.debt-card.status-unpaid { border-left-color: var(--primary); }

.debt-name { font-weight: 700; font-size: 16px; margin-bottom: 4px; }
.debt-meta { font-size: 13px; color: var(--text-muted); }
.debt-card-right { text-align: right; flex-shrink: 0; }
.debt-amount { font-weight: 700; font-size: 16px; }
.debt-paid-sub { font-size: 12px; color: var(--text-muted); margin-top: 2px; }

.badge {
    display: inline-block;
    padding: 3px 10px;
    border-radius: 20px;
    font-size: 11px;
    font-weight: 700;
    margin-top: 6px;
}
.badge-unpaid { background: #dbeafe; color: var(--primary); }
.badge-overdue { background: var(--red-bg); color: var(--red); }
.badge-partial { background: var(--amber-bg); color: var(--amber); }
.badge-paid { background: var(--green-bg); color: var(--green); }

.empty-state {
    text-align: center;
    padding: 60px 20px;
    color: var(--text-muted);
}
.empty-state p { margin-bottom: 16px; }

/* --- Forms --- */
.page-header { margin-bottom: 16px; }
.back-link { color: var(--text-muted); text-decoration: none; font-size: 14px; display: inline-block; margin-bottom: 8px; }
.page-header h2 { font-size: 20px; }

.card-form {
    background: #fff;
    border-radius: 14px;
    padding: 20px;
    border: 1px solid var(--border);
    margin-bottom: 16px;
}
.card-form h3 { margin-bottom: 14px; font-size: 16px; }
.form-group { margin-bottom: 14px; }
.form-group label { display: block; font-size: 13px; font-weight: 600; margin-bottom: 6px; color: var(--text-muted); }
.form-group input, .form-group select, .form-group textarea {
    width: 100%;
    padding: 11px 12px;
    border: 1px solid var(--border);
    border-radius: 10px;
    font-size: 15px;
    font-family: inherit;
}
.form-row { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
.radio-toggle { display: flex; gap: 16px; font-size: 14px; }
.radio-toggle label { display: flex; align-items: center; gap: 6px; font-weight: normal; color: var(--text); }
.hidden { display: none; }

.alert { padding: 12px 16px; border-radius: 10px; margin-bottom: 16px; font-size: 14px; }
.alert-error { background: var(--red-bg); color: var(--red); border: 1px solid #fecaca; }
.alert-success { background: var(--green-bg); color: var(--green); border: 1px solid #bbf7d0; }

/* --- Detail page --- */
.detail-card {
    background: #fff;
    border-radius: 14px;
    padding: 20px;
    border: 1px solid var(--border);
    border-top: 4px solid var(--border);
    margin-bottom: 16px;
}
.detail-card.status-overdue { border-top-color: var(--red); }
.detail-card.status-partial { border-top-color: var(--amber); }
.detail-card.status-paid { border-top-color: var(--green); }
.detail-card.status-unpaid { border-top-color: var(--primary); }

.detail-top { display: flex; justify-content: space-between; align-items: flex-start; margin-bottom: 16px; }
.detail-top h2 { font-size: 20px; }
.detail-phone { color: var(--text-muted); font-size: 14px; margin-top: 4px; }

.detail-amounts {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 10px;
    background: var(--gray-bg);
    border-radius: 10px;
    padding: 14px;
    margin-bottom: 16px;
}
.amount-box { text-align: center; }
.amount-label { font-size: 12px; color: var(--text-muted); margin-bottom: 4px; }
.amount-value { font-weight: 700; font-size: 15px; }
.amount-green { color: var(--green); }
.amount-red { color: var(--red); }

.detail-info { font-size: 14px; line-height: 1.8; margin-bottom: 16px; color: var(--text); }
.detail-info strong { color: var(--text-muted); font-weight: 600; }
.detail-actions { display: flex; gap: 10px; }

.payment-list { display: flex; flex-direction: column; gap: 10px; }
.payment-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 0;
    border-bottom: 1px solid var(--border);
}
.payment-item:last-child { border-bottom: none; }
.payment-amount { font-weight: 700; color: var(--green); font-size: 14px; }
.payment-date { font-size: 12px; color: var(--text-muted); margin-top: 2px; }
.btn-icon-delete {
    background: none;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    font-size: 16px;
    padding: 4px 8px;
}
.btn-icon-delete:hover { color: var(--red); }

/* --- Modal --- */
.modal {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.4);
    align-items: center;
    justify-content: center;
    z-index: 100;
    padding: 20px;
}
.modal.show { display: flex; }
.modal-content {
    background: #fff;
    border-radius: 14px;
    padding: 24px;
    max-width: 380px;
    width: 100%;
}
.modal-content h3 { margin-bottom: 10px; }
.modal-content p { color: var(--text-muted); font-size: 14px; margin-bottom: 20px; }
.modal-actions { display: flex; gap: 10px; justify-content: flex-end; }

/* --- Responsive --- */
@media (max-width: 600px) {
    .stats-grid { grid-template-columns: 1fr; }
    .stat-card { display: flex; justify-content: space-between; align-items: center; }
    .form-row { grid-template-columns: 1fr; }
    .toolbar { flex-direction: column; align-items: stretch; }
    .btn-add { margin-left: 0; }
    .debt-card { flex-wrap: wrap; }
    .detail-amounts { grid-template-columns: 1fr; }
}