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

/* ===== Design tokens ===== */
:root {
  --ink:        #1a1a18;
  --ink-muted:  #5a5a54;
  --ink-faint:  #9a9a94;
  --paper:      #f7f6f2;
  --surface:    #ffffff;
  --surface-2:  #f2f1ed;
  --border:     rgba(0,0,0,0.09);
  --border-md:  rgba(0,0,0,0.15);

  --blue:       #3B8BD4;
  --blue-light: #e8f2fb;
  --blue-mid:   rgba(59,139,212,0.3);
  --green:      #1D9E75;
  --orange:     #E85D24;
  --orange-dim: rgba(232,93,36,0.12);

  --r-sm: 5px;
  --r-md: 10px;
  --r-lg: 16px;

  --font-body:  'Noto Serif SC', 'PingFang SC', 'Hiragino Sans GB', serif;
  --font-mono:  'JetBrains Mono', 'Menlo', monospace;
}

html, body {
  height: 100%;
  font-family: var(--font-body);
  background: var(--paper);
  color: var(--ink);
  font-size: 13.5px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

/* ===== App shell ===== */
.app {
  display: flex;
  flex-direction: column;
  height: 100vh;
  overflow: hidden;
}

/* ===== Header ===== */
.app-header {
  flex-shrink: 0;
  height: 50px;
  background: var(--surface);
  border-bottom: 1px solid var(--border-md);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 24px;
}
.header-brand {
  display: flex;
  align-items: center;
  gap: 10px;
}
.badge {
  font-family: var(--font-mono);
  font-size: 9px;
  font-weight: 500;
  letter-spacing: .12em;
  padding: 3px 7px;
  border-radius: 3px;
  background: var(--ink);
  color: #fff;
}
.header-title {
  font-size: 14px;
  font-weight: 600;
  color: var(--ink);
  letter-spacing: .01em;
}
.header-meta {
  font-size: 12px;
  color: var(--ink-faint);
  font-family: var(--font-mono);
}

/* ===== Three-column layout ===== */
.main-layout {
  flex: 1;
  display: grid;
  grid-template-columns: 300px 1fr 220px;
  overflow: hidden;
}

/* ===== COL 1: Steps ===== */
.col-steps {
  display: flex;
  flex-direction: column;
  background: var(--surface);
  border-right: 1px solid var(--border-md);
  overflow: hidden;
}

.tab-bar {
  display: flex;
  border-bottom: 1px solid var(--border-md);
  flex-shrink: 0;
}
.tab {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 11px 0;
  font-size: 12.5px;
  font-weight: 500;
  color: var(--ink-muted);
  background: none;
  border: none;
  border-bottom: 2px solid transparent;
  cursor: pointer;
  transition: color .15s, border-color .15s;
  font-family: var(--font-body);
}
.tab:hover { color: var(--ink); }
.tab.active {
  color: var(--ink);
  border-bottom-color: var(--ink);
}
.tab-no {
  font-family: var(--font-mono);
  font-size: 10px;
  color: var(--ink-faint);
}
.tab.active .tab-no { color: var(--blue); }

.steps-scroll {
  flex: 1;
  overflow-y: auto;
  padding: 12px 10px 8px;
  scrollbar-width: thin;
  scrollbar-color: var(--border-md) transparent;
}
.steps-scroll::-webkit-scrollbar { width: 3px; }
.steps-scroll::-webkit-scrollbar-thumb { background: var(--border-md); border-radius: 2px; }

/* Step items */
.step-item {
  position: relative;
  padding: 10px 12px 10px 36px;
  border-radius: var(--r-md);
  margin-bottom: 4px;
  cursor: pointer;
  border: 1px solid transparent;
  transition: background .15s, border-color .15s;
  user-select: none;
}
.step-item::before {
  content: attr(data-idx);
  position: absolute;
  left: 12px;
  top: 11px;
  font-family: var(--font-mono);
  font-size: 10px;
  color: var(--ink-faint);
  line-height: 1;
}
.step-item:hover { background: var(--surface-2); }
.step-item.active {
  background: var(--blue-light);
  border-color: var(--blue-mid);
}
.step-item.active::before { color: var(--blue); }

.step-num {
  font-size: 10px;
  font-weight: 600;
  color: var(--ink-faint);
  margin-bottom: 3px;
  font-family: var(--font-mono);
  letter-spacing: .04em;
}
.step-item.active .step-num { color: var(--blue); }

.step-text {
  font-size: 13px;
  color: var(--ink);
  line-height: 1.55;
}

.step-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 4px;
  margin-top: 7px;
}
.tag {
  font-size: 10.5px;
  font-family: var(--font-mono);
  padding: 2px 7px;
  border-radius: 3px;
  border: 1px solid var(--border-md);
  color: var(--ink-muted);
  background: var(--surface);
}
.step-item.active .tag {
  color: var(--blue);
  border-color: var(--blue-mid);
  background: var(--surface);
}

/* API panel */
.api-panel {
  flex-shrink: 0;
  padding: 12px 12px 14px;
  border-top: 1px solid var(--border);
  background: #fafaf8;
}
.api-label {
  font-size: 10.5px;
  color: var(--ink-faint);
  margin-bottom: 7px;
  font-family: var(--font-mono);
  letter-spacing: .02em;
}
.api-row { display: flex; gap: 6px; }
.api-input {
  flex: 1;
  min-width: 0;
  font-size: 12px;
  font-family: var(--font-mono);
  padding: 6px 9px;
  border-radius: var(--r-sm);
  border: 1px solid var(--border-md);
  background: var(--surface);
  color: var(--ink);
  outline: none;
  transition: border-color .15s;
}
.api-input:focus { border-color: var(--blue); }
.api-btn {
  font-size: 12px;
  font-weight: 500;
  font-family: var(--font-body);
  padding: 6px 14px;
  border-radius: var(--r-sm);
  border: 1px solid var(--border-md);
  background: var(--surface);
  color: var(--ink);
  cursor: pointer;
  transition: background .15s;
}
.api-btn:hover { background: var(--surface-2); }
.api-btn:disabled { opacity: .4; cursor: not-allowed; }
.api-status {
  font-size: 10.5px;
  font-family: var(--font-mono);
  color: var(--ink-faint);
  margin-top: 6px;
  min-height: 15px;
}
.api-status.ok  { color: var(--green); }
.api-status.err { color: #c44; }

/* ===== COL 2: Geometry ===== */
.col-geo {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 28px 24px 20px;
  gap: 16px;
  background: var(--paper);
  overflow: hidden;
}

.geo-title {
  font-size: 12.5px;
  font-family: var(--font-mono);
  color: var(--ink-muted);
  text-align: center;
  letter-spacing: .02em;
}

.geo-card {
  background: var(--surface);
  border-radius: var(--r-lg);
  border: 1px solid var(--border-md);
  box-shadow:
    0 1px 2px rgba(0,0,0,0.04),
    0 4px 16px rgba(0,0,0,0.06),
    0 0 0 0.5px rgba(0,0,0,0.04) inset;
  padding: 20px;
  width: 100%;
  max-width: 440px;
}

#geo-svg {
  display: block;
  width: 100%;
  overflow: visible;
}

.v-label {
  font-family: var(--font-mono);
  font-size: 15px;
  font-weight: 500;
  fill: #1a1a18;
}
.v-label-sm {
  font-family: var(--font-mono);
  font-size: 12px;
  fill: #999;
}
.dim-label {
  font-family: var(--font-mono);
  font-size: 14px;
  font-weight: 500;
  fill: var(--orange);
}
.dim-label-sub {
  font-family: var(--font-body);
  font-size: 11px;
  fill: var(--ink-muted);
}

/* Legend */
.legend {
  display: flex;
  gap: 16px;
  justify-content: center;
}
.leg-item {
  display: flex;
  align-items: center;
  gap: 5px;
  font-size: 11.5px;
  color: var(--ink-muted);
}
.leg-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  flex-shrink: 0;
}
.leg-dot.blue   { background: var(--blue); }
.leg-dot.green  { background: var(--green); }
.leg-dot.orange { background: var(--orange); }

/* ===== COL 3: Info panel ===== */
.col-info {
  display: flex;
  flex-direction: column;
  gap: 0;
  background: var(--surface);
  border-left: 1px solid var(--border-md);
  overflow-y: auto;
  scrollbar-width: none;
}
.col-info::-webkit-scrollbar { display: none; }

.info-section {
  padding: 16px 16px 14px;
  border-bottom: 1px solid var(--border);
}

.info-heading {
  font-size: 10px;
  font-family: var(--font-mono);
  font-weight: 500;
  letter-spacing: .1em;
  text-transform: uppercase;
  color: var(--ink-faint);
  margin-bottom: 10px;
}

/* Conditions */
.cond-row {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  padding: 4px 0;
  border-bottom: 1px dashed var(--border);
}
.cond-row:last-child { border-bottom: none; }
.cond-key { font-size: 12px; color: var(--ink-muted); }
.cond-val {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--ink);
  font-weight: 500;
}

/* Step detail */
.step-detail-box {
  background: var(--orange-dim);
  border-radius: var(--r-md);
  border: 1px solid rgba(232,93,36,0.18);
  padding: 12px;
  min-height: 80px;
}
.step-detail-hint {
  font-size: 11.5px;
  color: var(--ink-faint);
}
.detail-num {
  font-family: var(--font-mono);
  font-size: 10px;
  color: var(--orange);
  margin-bottom: 6px;
  letter-spacing: .06em;
}
.detail-text {
  font-size: 12.5px;
  color: var(--ink);
  line-height: 1.6;
}
.detail-dim {
  margin-top: 10px;
  font-family: var(--font-mono);
  font-size: 15px;
  font-weight: 500;
  color: var(--orange);
  text-align: center;
  padding: 6px 0 2px;
  border-top: 1px solid rgba(232,93,36,0.2);
}

/* Formulas */
.formula-list { display: flex; flex-direction: column; gap: 8px; }
.formula-item {
  display: flex;
  flex-direction: column;
  gap: 2px;
  padding: 8px 10px;
  background: var(--surface-2);
  border-radius: var(--r-sm);
  border: 1px solid var(--border);
}
.formula-name {
  font-size: 10px;
  font-family: var(--font-mono);
  color: var(--ink-faint);
  letter-spacing: .06em;
  text-transform: uppercase;
}
.formula-expr {
  font-family: var(--font-mono);
  font-size: 12.5px;
  color: var(--ink);
}

/* ===== Transitions ===== */
#hl-base, #hl-face-PBC, #hl-face-PCD, #hl-face-PAB, #hl-face-PAD {
  transition: fill-opacity .35s ease;
}
circle { transition: fill .25s ease, r .2s ease; }