:root {
  --bg: #F7F8FA;
  --primary: #176B87;
  --primary-dark: #124F63;
  --secondary: #64CCC5;
  --accent: #F4C542;
  --success: #2E8B57;
  --warning: #F59E0B;
  --error: #DC3545;
  --text: #1F2937;
  --text-secondary: #6B7280;
  --card-bg: #FFFFFF;
  --border: #E5E9EE;
  --radius: 14px;
  --radius-sm: 10px;
  --tabbar-h: 64px;
  --topbar-h: 56px;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  height: 100%;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  -webkit-tap-highlight-color: transparent;
}

body {
  padding-top: calc(var(--topbar-h) + env(safe-area-inset-top));
  padding-bottom: calc(var(--tabbar-h) + env(safe-area-inset-bottom));
}

h1, h2, h3 { margin: 0 0 4px 0; line-height: 1.25; }
p { margin: 0 0 8px 0; }

.topbar {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: calc(var(--topbar-h) + env(safe-area-inset-top));
  padding-top: env(safe-area-inset-top);
  background: var(--primary);
  color: #fff;
  display: flex;
  align-items: center;
  z-index: 20;
  box-shadow: 0 1px 3px rgba(0,0,0,0.15);
}
.topbar-title {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 17px;
  font-weight: 600;
  padding: 0 16px;
}
.topbar-title .bolt { color: var(--accent); font-size: 20px; }

.view {
  max-width: 560px;
  margin: 0 auto;
  padding: 16px 16px 24px;
  min-height: calc(100vh - var(--topbar-h) - var(--tabbar-h));
}

.tabbar {
  position: fixed;
  bottom: 0; left: 0; right: 0;
  height: calc(var(--tabbar-h) + env(safe-area-inset-bottom));
  padding-bottom: env(safe-area-inset-bottom);
  background: #fff;
  border-top: 1px solid var(--border);
  display: flex;
  z-index: 20;
}
.tab {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 2px;
  text-decoration: none;
  color: var(--text-secondary);
  font-size: 11px;
  padding-top: 6px;
}
.tab-icon { font-size: 20px; }
.tab.active { color: var(--primary); font-weight: 600; }
.tab.active .tab-icon { transform: scale(1.05); }

/* ---------- Generic building blocks ---------- */

.card {
  background: var(--card-bg);
  border-radius: var(--radius);
  padding: 16px;
  margin-bottom: 14px;
  box-shadow: 0 1px 2px rgba(16,24,40,0.06);
  border: 1px solid var(--border);
}

.card-title {
  font-size: 15px;
  font-weight: 700;
  color: var(--primary-dark);
  margin-bottom: 10px;
}

.section-title {
  font-size: 13px;
  font-weight: 700;
  text-transform: none;
  color: var(--text-secondary);
  margin: 18px 0 8px;
}

.field {
  margin-bottom: 12px;
}
.field label {
  display: block;
  font-size: 13px;
  color: var(--text-secondary);
  margin-bottom: 4px;
}
.field input[type="number"],
.field input[type="text"],
.field select {
  width: 100%;
  font-size: 17px;
  padding: 12px 12px;
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  background: #fff;
  color: var(--text);
  -moz-appearance: textfield;
}
.field input:focus, .field select:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(23,107,135,0.12);
}
.field input[readonly] {
  background: #F0F3F5;
  color: var(--text-secondary);
}
.field-hint { font-size: 12px; color: var(--text-secondary); margin-top: 4px; }

.row-2 {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  font-size: 15px;
  font-weight: 600;
  padding: 13px 18px;
  border-radius: var(--radius-sm);
  border: none;
  cursor: pointer;
  text-decoration: none;
  width: 100%;
  min-height: 48px;
}
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:active { background: var(--primary-dark); }
.btn-secondary { background: #E8F6F5; color: var(--primary-dark); }
.btn-outline { background: transparent; color: var(--primary); border: 1.5px solid var(--primary); }
.btn-success { background: var(--success); color: #fff; }
.btn-warning { background: var(--warning); color: #fff; }
.btn-danger-outline { background: transparent; color: var(--error); border: 1.5px solid var(--error); }
.btn-sm { padding: 10px 14px; font-size: 13px; min-height: 40px; width: auto; }
.btn-row { display: flex; gap: 10px; }
.btn-row .btn { flex: 1; }
.btn[disabled] { opacity: 0.5; pointer-events: none; }

.chip {
  display: inline-flex;
  align-items: center;
  padding: 3px 10px;
  border-radius: 100px;
  font-size: 12px;
  font-weight: 600;
}
.chip-active { background: #E6F4EA; color: var(--success); }
.chip-inactive { background: #F1F2F4; color: var(--text-secondary); }

.month-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: var(--primary);
  color: #fff;
  border-radius: var(--radius);
  padding: 10px 6px;
  margin-bottom: 16px;
}
.month-nav button {
  background: rgba(255,255,255,0.15);
  border: none;
  color: #fff;
  width: 40px;
  height: 40px;
  border-radius: 10px;
  font-size: 18px;
  cursor: pointer;
}
.month-nav .month-label {
  font-size: 16px;
  font-weight: 700;
  text-align: center;
}

.summary-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
  margin-bottom: 14px;
}
.summary-item {
  background: #fff;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 12px;
}
.summary-item .val {
  font-size: 18px;
  font-weight: 700;
  color: var(--primary-dark);
}
.summary-item .val.accent { color: #9A7300; }
.summary-item .label {
  font-size: 12px;
  color: var(--text-secondary);
  margin-top: 2px;
}

.occupant-card {
  background: #fff;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
  margin-bottom: 14px;
}
.occupant-name {
  font-size: 16px;
  font-weight: 700;
  margin-bottom: 8px;
  color: var(--text);
}
.occupant-rows {
  display: flex;
  flex-direction: column;
  gap: 4px;
  margin-bottom: 12px;
}
.occupant-row {
  display: flex;
  justify-content: space-between;
  font-size: 14px;
  color: var(--text-secondary);
}
.occupant-row b { color: var(--text); font-weight: 600; }
.occupant-row.kwh-accent b { color: #9A7300; }

.total-pay {
  background: #EAF3F1;
  border-radius: var(--radius-sm);
  padding: 14px;
  text-align: center;
  margin-bottom: 12px;
}
.total-pay .label { font-size: 13px; color: var(--text-secondary); margin-bottom: 2px; }
.total-pay .amount { font-size: 28px; font-weight: 800; color: var(--primary-dark); }

.alert {
  border-radius: var(--radius-sm);
  padding: 12px 14px;
  font-size: 14px;
  margin-bottom: 14px;
  line-height: 1.4;
}
.alert-error { background: #FBEAEC; color: #8A1F2C; border: 1px solid #F1C0C6; }
.alert-warning { background: #FFF6E5; color: #7A4E00; border: 1px solid #F7DFA3; }
.alert-success { background: #E9F5EE; color: #1D6B44; border: 1px solid #BFE3CD; }
.alert ul { margin: 6px 0 0 18px; padding: 0; }

.empty-state {
  text-align: center;
  padding: 40px 16px;
  color: var(--text-secondary);
}
.empty-state .icon { font-size: 40px; margin-bottom: 10px; }

.toast {
  position: fixed;
  left: 50%;
  bottom: calc(var(--tabbar-h) + env(safe-area-inset-bottom) + 14px);
  transform: translateX(-50%) translateY(20px);
  background: var(--text);
  color: #fff;
  padding: 12px 18px;
  border-radius: 100px;
  font-size: 14px;
  z-index: 50;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.2s ease, transform 0.2s ease;
  max-width: 90vw;
  text-align: center;
}
.toast.show {
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}

.divider {
  height: 1px;
  background: var(--border);
  margin: 16px 0;
}

.list-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  padding: 12px 0;
  border-bottom: 1px solid var(--border);
}
.list-item:last-child { border-bottom: none; }
.list-item-name { font-weight: 600; font-size: 15px; }
.list-item-actions { display: flex; gap: 8px; }
.icon-btn {
  background: #F0F3F5;
  border: none;
  border-radius: 8px;
  width: 36px;
  height: 36px;
  font-size: 15px;
  cursor: pointer;
}

.radio-group { display: flex; flex-direction: column; gap: 8px; margin-bottom: 12px; }
.radio-option {
  display: flex;
  align-items: center;
  gap: 10px;
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 12px;
  cursor: pointer;
}
.radio-option.selected { border-color: var(--primary); background: #F0F8F8; }
.radio-option input { margin: 0; }

.month-check-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
  margin-bottom: 12px;
}
.month-check {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 13px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 8px;
}

.app-footer-note {
  text-align: center;
  color: var(--text-secondary);
  font-size: 12px;
  margin-top: 24px;
  line-height: 1.5;
}

@media (min-width: 600px) {
  .view { padding: 24px 20px 32px; }
}