:root {
  --bg: #f5f7fa;
  --surface: #ffffff;
  --border: #dde1e7;
  --text: #1c2128;
  --text-muted: #5b6370;
  --accent-blue: #1a6fc4;
  --accent-red: #c0392b;
  --accent-gold: #b45309;
  --accent-green: #1e7e4e;
  --accent-purple: #6d28d9;
  --font-mono: 'Courier New', monospace;
  --font-sans: 'Segoe UI', system-ui, sans-serif;
  --radius: 6px;
  --hint-bg: #eff6ff;
  --hint-border: #93c5fd;
  --hint-text: #1e3a8a;
}

html { font-size: 17px; }

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

body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
  line-height: 1.6;
}

.navbar {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 12px 24px;
  display: flex;
  align-items: center;
  gap: 24px;
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: 0 1px 3px rgba(0,0,0,.06);
}

/* QR Code */
.qr-wrap { margin-left: auto; position: relative; }
.qr-btn {
  display: flex;
  align-items: center;
  gap: 5px;
  padding: 5px 10px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--text-muted);
  font-size: 0.78rem;
  cursor: pointer;
  transition: border-color .2s, color .2s;
}
.qr-btn:hover { border-color: var(--accent-blue); color: var(--accent-blue); }
.qr-popup {
  display: none;
  position: absolute;
  right: 0;
  top: calc(100% + 8px);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 14px;
  box-shadow: 0 6px 20px rgba(0,0,0,.12);
  text-align: center;
  z-index: 200;
  white-space: nowrap;
}
.qr-popup p { font-size: 0.75rem; color: var(--text-muted); margin-top: 8px; }
.qr-popup.open { display: block; }

.navbar-brand {
  color: var(--accent-blue);
  font-weight: 700;
  font-size: 1rem;
  text-decoration: none;
}

.navbar-link {
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.875rem;
  transition: color 0.2s;
}

.navbar-link:hover, .navbar-link.active { color: var(--text); }

.page-header {
  padding: 28px 24px 16px;
  border-bottom: 1px solid var(--border);
}

.page-header h1 { font-size: 1.4rem; margin-bottom: 4px; }
.page-header p { color: var(--text-muted); font-size: 0.95rem; }

.container { padding: 20px 24px; }

/* 概念卡 */
.concept-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 10px;
  margin-bottom: 20px;
}

.concept-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
}

.lhp-card .concept-card-header  { border-left: 3px solid var(--accent-blue); }
.rhp-card .concept-card-header  { border-left: 3px solid var(--accent-red); }
.jw-card  .concept-card-header  { border-left: 3px solid var(--accent-gold); }
.rhpz-card .concept-card-header { border-left: 3px solid #a78bfa; }

.concept-card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 14px;
  cursor: pointer;
  user-select: none;
  font-weight: 600;
  font-size: 0.83rem;
  gap: 8px;
}

.concept-card-header:hover { background: rgba(0,0,0,0.04); }

.concept-card-body {
  padding: 10px 14px;
  border-top: 1px solid var(--border);
  font-size: 0.9rem;
  color: var(--text-muted);
}

.concept-card-body p { margin-bottom: 6px; }

.formula {
  background: var(--bg);
  border-left: 3px solid rgba(255, 215, 0, 0.35);
  border-radius: 4px;
  padding: 4px 14px 8px;
  margin: 4px 0 8px;
  overflow-x: auto;
  color: var(--text);
}

.formula-caption {
  margin: 8px 0 2px;
  font-size: 0.83rem;
  color: var(--text-muted);
  font-style: italic;
}

.load-btn {
  margin-top: 8px;
  padding: 3px 10px;
  font-size: 0.76rem;
  background: transparent;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--accent-blue);
  cursor: pointer;
  transition: border-color 0.2s, background 0.2s;
}

.load-btn:hover {
  border-color: var(--accent-blue);
  background: rgba(74,158,255,0.1);
}

/* 預設情境列 */
.preset-bar {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
  margin-bottom: 14px;
  align-items: center;
}

.preset-bar > label { font-size: 0.76rem; color: var(--text-muted); }

.preset-btn {
  padding: 4px 10px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--text);
  font-size: 0.78rem;
  cursor: pointer;
  transition: border-color 0.2s, background 0.2s;
}

.preset-btn:hover {
  border-color: var(--accent-blue);
  background: rgba(74,158,255,0.08);
}

/* 互動主區 */
.interactive-area {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
}

@media (max-width: 900px) {
  .interactive-area { grid-template-columns: 1fr; }
}

.panel {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
}

.panel-header {
  padding: 7px 12px;
  border-bottom: 1px solid var(--border);
  font-size: 0.76rem;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.panel-body { padding: 6px; }

/* s 平面工具列 */
.splane-toolbar {
  display: flex;
  gap: 5px;
  padding: 5px 8px;
  border-bottom: 1px solid var(--border);
  flex-wrap: wrap;
  align-items: center;
}

.tool-btn {
  padding: 3px 9px;
  border: 1px solid var(--border);
  border-radius: 4px;
  background: transparent;
  color: var(--text-muted);
  font-size: 0.74rem;
  cursor: pointer;
  transition: all 0.15s;
}

.tool-btn.active {
  border-color: var(--accent-blue);
  color: var(--accent-blue);
  background: rgba(74,158,255,0.1);
}

.tool-btn.delete-btn.active {
  border-color: var(--accent-red);
  color: var(--accent-red);
  background: rgba(255,107,107,0.1);
}

.tool-btn:hover { color: var(--text); }

.gain-label {
  font-size: 0.74rem;
  color: var(--text-muted);
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: 5px;
}

.gain-label input {
  width: 54px;
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--text);
  border-radius: 4px;
  padding: 2px 5px;
  font-size: 0.74rem;
}

/* 右側三圖 */
.right-panels { display: flex; flex-direction: column; gap: 10px; }

/* 軸樣式 */
.axis-style line, .axis-style path { stroke: var(--border); }
.axis-style text { fill: var(--text-muted); font-size: 9px; }

/* 極點/零點符號 */
.pole-x {
  font-size: 20px;
  font-weight: 700;
  cursor: grab;
  user-select: none;
}
.pole-x:active { cursor: grabbing; }
.pole-lhp { fill: var(--accent-blue); }
.pole-rhp { fill: var(--accent-red); }

.zero-circle {
  fill: none;
  stroke-width: 2.5;
  cursor: grab;
}
.zero-circle:active { cursor: grabbing; }
.zero-lhp { stroke: var(--accent-gold); }
.zero-rhp { stroke: #a78bfa; }

/* 刪除模式：游標改為指標，懸停時變紅 */
.delete-mode .pole-x,
.delete-mode .zero-circle {
  cursor: pointer;
}
.delete-mode .pole-x:hover { fill: var(--accent-red); opacity: 0.8; }
.delete-mode .zero-circle:hover { stroke: var(--accent-red); opacity: 0.8; }

@keyframes rhp-pulse {
  0%, 100% { opacity: 0.12; transform: scale(1); }
  50%       { opacity: 0.32; transform: scale(1.5); }
}

.rhp-glow {
  fill: var(--accent-red);
  animation: rhp-pulse 1.2s ease-in-out infinite;
  pointer-events: none;
  transform-box: fill-box;
  transform-origin: center;
}

/* 系統資訊面板 */
.info-panel { padding: 10px 12px; font-size: 0.79rem; }

.info-row {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  padding: 3px 0;
  border-bottom: 1px solid var(--border);
}

.info-label { color: var(--text-muted); }
.info-value { font-family: var(--font-mono); }
.info-value.stable   { color: var(--accent-green); }
.info-value.unstable { color: var(--accent-red); }
.info-value.marginal { color: var(--accent-gold); }

.pole-list, .zero-list { font-family: var(--font-mono); font-size: 0.74rem; margin-top: 4px; }
.pole-entry         { color: var(--accent-blue); }
.pole-entry.rhp     { color: var(--accent-red); }
.zero-entry         { color: var(--accent-gold); }

/* 深入說明區 */
.deep-section {
  margin-top: 28px;
  padding-top: 20px;
  border-top: 1px solid var(--border);
}

.deep-section h2 { font-size: 1.1rem; color: var(--text-muted); margin-bottom: 14px; }
.deep-section h3 { font-size: 0.96rem; color: var(--accent-blue); margin: 14px 0 6px; }
.deep-section p  { font-size: 0.9rem; color: var(--text-muted); margin-bottom: 6px; }

/* ═══════════════════════════════════════════════
   差動對 Wizard 樣式
═══════════════════════════════════════════════ */
.type-toggle-bar {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 16px;
  font-size: 0.875rem;
  color: var(--text-muted);
}

.type-btn {
  background: var(--surface);
  border: 1px solid var(--border);
  color: var(--text-muted);
  padding: 5px 14px;
  border-radius: var(--radius);
  cursor: pointer;
  font-size: 0.875rem;
  transition: border-color 0.2s, color 0.2s;
}

.type-btn.active {
  border-color: var(--accent-blue);
  color: var(--accent-blue);
}

.wizard-layout {
  display: flex;
  gap: 0;
  min-height: 520px;
}

.wizard-sidebar {
  width: 200px;
  flex-shrink: 0;
  border-right: 1px solid var(--border);
  padding: 16px 0;
}

.wizard-step-list {
  list-style: none;
}

.wizard-step-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 16px;
  cursor: pointer;
  color: var(--text-muted);
  font-size: 0.875rem;
  border-left: 3px solid transparent;
  transition: color 0.2s, border-color 0.2s;
}

.wizard-step-item:hover { color: var(--text); }

.wizard-step-item.active {
  color: var(--text);
  border-left-color: var(--accent-blue);
}

.wizard-step-item.done {
  color: var(--accent-green);
}

.step-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--border);
  flex-shrink: 0;
  transition: background 0.2s;
}

.wizard-step-item.active .step-dot { background: var(--accent-blue); }
.wizard-step-item.done  .step-dot  { background: var(--accent-green); }

.wizard-content {
  flex: 1;
  padding: 24px;
  display: flex;
  flex-direction: column;
}

.step-panel { display: none; flex: 1; flex-direction: column; }
.step-panel.active { display: flex; }

.step-title {
  font-size: 1.1rem;
  margin-bottom: 16px;
  color: var(--text);
}

.step-body {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.circuit-wrap {
  width: 100%;
  max-width: 520px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 8px;
}

/* 控制列：滑桿（左）+ 圖表（右）橫排 */
.step-controls {
  display: flex;
  gap: 24px;
  align-items: flex-start;
}

.controls-sliders {
  flex: 0 0 220px;
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.controls-chart {
  flex: 1;
}

.control-group {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.control-group label {
  font-size: 0.875rem;
  color: var(--text-muted);
}

.control-group input[type="range"] {
  width: 100%;
  accent-color: var(--accent-blue);
}

.hint-box {
  background: var(--hint-bg);
  border: 1px solid var(--hint-border);
  border-radius: var(--radius);
  padding: 10px 12px;
  font-size: 0.85rem;
  color: var(--hint-text);
  line-height: 1.5;
}

.wizard-nav {
  display: flex;
  justify-content: space-between;
  margin-top: 20px;
  padding-top: 16px;
  border-top: 1px solid var(--border);
}

/* 小訊號公式卡片 */
.formula-cards {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-bottom: 16px;
}

.formula-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px;
}

.formula-card h4 {
  font-size: 0.8rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 8px;
}

.live-values {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
}

.live-val-item { text-align: center; }
.live-val-item .val-num {
  font-size: 1.3rem;
  font-family: var(--font-mono);
  color: var(--accent-blue);
}
.live-val-item .val-label {
  font-size: 0.75rem;
  color: var(--text-muted);
  margin-top: 2px;
}

/* 比較表 */
.compare-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.875rem;
  margin-top: 16px;
}

.compare-table th,
.compare-table td {
  border: 1px solid var(--border);
  padding: 8px 12px;
  text-align: left;
}

.compare-table th {
  background: var(--surface);
  color: var(--text-muted);
  font-weight: 600;
}

.compare-table tr:nth-child(even) td { background: #f0f3f6; }