:root {
    --bg: #0f172a;
    --panel-bg: #1e293b;
    --panel-bg-alt: #16213a;
    --accent: #38bdf8;
    --accent-hover: #7dd3fc;
    --text: #f1f5f9;
    --text-muted: #94a3b8;
    --border: rgba(148, 163, 184, 0.18);
    --success: #34d399;
    --danger: #f87171;
    --warning: #fbbf24;
}

* { box-sizing: border-box; }

body {
    margin: 0;
    min-height: 100vh;
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
    background: var(--bg);
    color: var(--text);
    display: flex;
}

a { color: var(--accent); }

.sidebar {
    width: 220px;
    flex-shrink: 0;
    background: var(--panel-bg-alt);
    border-right: 1px solid var(--border);
    padding: 1.25rem 0;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

.sidebar .brand {
    font-weight: 700;
    font-size: 1.1rem;
    color: var(--accent);
    padding: 0 1.25rem 1.25rem 1.25rem;
    border-bottom: 1px solid var(--border);
    margin-bottom: 0.75rem;
}

.sidebar nav a {
    display: block;
    padding: 0.6rem 1.25rem;
    color: var(--text-muted);
    text-decoration: none;
    font-size: 0.92rem;
    border-left: 3px solid transparent;
}

.sidebar nav a:hover { color: var(--text); background: rgba(148,163,184,0.06); }
.sidebar nav a.active { color: var(--accent); border-left-color: var(--accent); background: rgba(56,189,248,0.08); }

.sidebar .spacer { flex: 1; }

.sidebar .logout {
    padding: 0.6rem 1.25rem;
    color: var(--text-muted);
    text-decoration: none;
    font-size: 0.85rem;
    border-top: 1px solid var(--border);
    cursor: pointer;
}
.sidebar .logout:hover { color: var(--danger); }

main {
    flex: 1;
    padding: 2rem 2.5rem;
    max-width: 1200px;
}

h1 { margin-top: 0; font-size: 1.6rem; }
h2 { font-size: 1.1rem; color: var(--text-muted); font-weight: 600; text-transform: uppercase; letter-spacing: 0.03em; }

.card {
    background: var(--panel-bg);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 1.25rem 1.5rem;
    margin-bottom: 1.5rem;
}

.stat-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    gap: 1rem;
    margin-bottom: 1.5rem;
}
.stat-grid .stat { background: var(--panel-bg); border: 1px solid var(--border); border-radius: 10px; padding: 1rem 1.25rem; }
.stat .label { color: var(--text-muted); font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.04em; }
.stat .value { font-size: 1.6rem; font-weight: 700; margin-top: 0.25rem; }
.stat .value.neg { color: var(--danger); }
.stat .value.pos { color: var(--success); }

table { width: 100%; border-collapse: collapse; font-size: 0.9rem; }
th, td { text-align: left; padding: 0.55rem 0.7rem; border-bottom: 1px solid var(--border); }
th { color: var(--text-muted); font-weight: 600; font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.03em; }
td.num, th.num { text-align: right; font-variant-numeric: tabular-nums; }
tr:hover td { background: rgba(148,163,184,0.04); }

.btn {
    display: inline-block;
    background: var(--accent);
    color: #0f172a;
    border: none;
    padding: 0.5rem 1rem;
    border-radius: 6px;
    font-weight: 600;
    font-size: 0.85rem;
    cursor: pointer;
    text-decoration: none;
}
.btn:hover { background: var(--accent-hover); }
.btn.secondary { background: transparent; color: var(--text); border: 1px solid var(--border); }
.btn.secondary:hover { border-color: var(--accent); color: var(--accent); }
.btn.danger { background: var(--danger); color: #1c0a0a; }
.btn.small { padding: 0.3rem 0.65rem; font-size: 0.78rem; }

input, select, textarea {
    background: var(--bg);
    border: 1px solid var(--border);
    color: var(--text);
    padding: 0.5rem 0.65rem;
    border-radius: 6px;
    font-size: 0.88rem;
    font-family: inherit;
}
input:focus, select:focus, textarea:focus { outline: none; border-color: var(--accent); }

label { display: block; font-size: 0.8rem; color: var(--text-muted); margin-bottom: 0.25rem; }
.field { margin-bottom: 0.85rem; }
.field-row { display: flex; gap: 1rem; flex-wrap: wrap; }
.field-row .field { flex: 1; min-width: 160px; }

.badge { display: inline-block; padding: 0.15rem 0.55rem; border-radius: 999px; font-size: 0.72rem; font-weight: 600; }
.badge.paid { background: rgba(52,211,153,0.15); color: var(--success); }
.badge.unpaid { background: rgba(248,113,113,0.15); color: var(--danger); }
.badge.pending { background: rgba(251,191,36,0.15); color: var(--warning); }

.toolbar { display: flex; justify-content: space-between; align-items: center; margin-bottom: 1rem; gap: 1rem; flex-wrap: wrap; }

.empty { color: var(--text-muted); font-style: italic; padding: 1rem 0; }

.modal-backdrop {
    position: fixed; inset: 0; background: rgba(0,0,0,0.55);
    display: flex; align-items: flex-start; justify-content: center;
    padding: 3rem 1rem; overflow-y: auto; z-index: 50;
}
.modal { background: var(--panel-bg); border: 1px solid var(--border); border-radius: 10px; padding: 1.5rem; width: 100%; max-width: 560px; }
.modal h2 { margin-top: 0; }
.modal .actions { display: flex; justify-content: flex-end; gap: 0.6rem; margin-top: 1.25rem; }

.error-text { color: var(--danger); font-size: 0.85rem; margin-top: 0.5rem; }

@media (max-width: 720px) {
    body { flex-direction: column; }
    .sidebar { width: 100%; min-height: auto; flex-direction: row; overflow-x: auto; padding: 0.5rem; }
    .sidebar .brand, .sidebar .spacer, .sidebar .logout { display: none; }
    .sidebar nav { display: flex; }
    .sidebar nav a { border-left: none; border-bottom: 3px solid transparent; white-space: nowrap; }
    .sidebar nav a.active { border-left-color: transparent; border-bottom-color: var(--accent); }
    main { padding: 1.25rem; }
}