:root {
  --bg:            #0a0a0a;
  --surface:       #111111;
  --surface-hover: #181818;
  --border:        #222222;
  --border-light:  #2a2a2a;
  --text:          #e0e0e0;
  --text-dim:      #666666;
  --text-muted:    #444444;
  --accent:        #ffffff;
  --accent-dim:    #aaaaaa;
  --green:         #4ade80;
  --red:           #f87171;
  --radius:        6px;
  --mono:          'IBM Plex Mono', monospace;
}

@font-face {
  font-family: 'IBM Plex Mono';
  font-style: normal;
  font-weight: 400;
  src: url(https://fonts.gstatic.com/s/ibmplexmono/v12/-F63fjptAgt5VM-kVkqdyU8n1i8q1w.woff2) format('woff2');
}

@font-face {
  font-family: 'IBM Plex Mono';
  font-style: normal;
  font-weight: 500;
  src: url(https://fonts.gstatic.com/s/ibmplexmono/v12/-F6qfjptAgt5VM-kVkqdyU8n3twJ0n1g.woff2) format('woff2');
}

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

body {
  font-family: var(--mono);
  background: var(--bg);
  color: var(--text);
  -webkit-font-smoothing: antialiased;
  display: flex;
  justify-content: center;
}

#app {
  max-width: 720px;
  width: 100%;
  padding: 3rem 1.5rem;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

/* --- tabs --- */

.tabs {
  display: flex;
  gap: 0;
  border-bottom: 1px solid var(--border);
  margin-bottom: 2.5rem;
}

.tab {
  font-family: var(--mono);
  font-size: 0.8rem;
  font-weight: 400;
  letter-spacing: 0.02em;
  color: var(--text-dim);
  background: none;
  border: none;
  border-bottom: 1px solid transparent;
  margin-bottom: -1px;
  padding: 0.5rem 1rem;
  cursor: pointer;
  transition: color 0.15s, border-color 0.15s;
}

.tab:hover { color: var(--text); }
.tab.active { color: var(--accent); border-bottom-color: var(--accent); }

/* --- hero --- */

.hero { margin-bottom: 2rem; }
.hero h1 {
  font-size: 1.5rem;
  font-weight: 500;
  letter-spacing: -0.02em;
}
.hero .tagline {
  font-size: 0.8rem;
  color: var(--text-dim);
  margin-top: 0.25rem;
}

/* --- preset bar --- */

/* --- model selection bar --- */

.model-bar {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 0.35rem;
  flex-wrap: wrap;
}

.model-btn {
  font-family: var(--mono);
  font-size: 0.72rem;
  font-weight: 400;
  color: var(--text-dim);
  background: none;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.35rem 0.75rem;
  cursor: pointer;
  transition: border-color 0.15s, color 0.15s;
}

.model-btn:hover { border-color: var(--text-dim); color: var(--text); }
.model-btn.active { border-color: var(--accent); color: var(--accent); }

.model-info {
  font-size: 0.65rem;
  color: var(--text-muted);
  min-height: 1em;
  margin-bottom: 0.5rem;
}

/* --- advanced toggle --- */

.advanced-toggle {
  font-family: var(--mono);
  font-size: 0.75rem;
  font-weight: 400;
  color: var(--text-muted);
  background: none;
  border: none;
  cursor: pointer;
  padding: 0.75rem 0;
  transition: color 0.15s;
  display: block;
  width: 100%;
  text-align: left;
}

.advanced-toggle:hover { color: var(--text-dim); }

.toggle-arrow {
  display: inline-block;
  margin-right: 0.25rem;
}

.advanced-params {
  border-top: 1px solid var(--border);
  padding-top: 1rem;
  margin-bottom: 1rem;
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

/* --- parameter sections --- */

.params {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
  margin-bottom: 1.5rem;
}

.param-section h3 {
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--accent);
  margin-bottom: 0.5rem;
}

.param-grid {
  display: grid;
  gap: 0.4rem 0.5rem;
  align-items: center;
}

.param-grid.cols-3 { grid-template-columns: auto 1fr 1fr; }
.param-grid.cols-2 { grid-template-columns: auto 1fr; }

.param-grid label {
  font-size: 0.72rem;
  color: var(--text-dim);
  white-space: nowrap;
}

.param-grid .col-header {
  font-size: 0.65rem;
  color: var(--text-muted);
  text-align: center;
}

.param-grid input {
  font-family: var(--mono);
  font-size: 0.78rem;
  color: var(--text);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.35rem 0.5rem;
  outline: none;
  width: 100%;
  min-width: 0;
  transition: border-color 0.15s;
}

.param-grid input:focus { border-color: var(--text-dim); }

/* hide number spinners */
input[type="number"]::-webkit-inner-spin-button,
input[type="number"]::-webkit-outer-spin-button {
  -webkit-appearance: none;
  margin: 0;
}
input[type="number"] { -moz-appearance: textfield; }

/* --- results --- */

.results-area { margin-bottom: 2rem; }

.summary {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.75rem;
  margin-bottom: 1.5rem;
}

.summary-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.75rem;
  padding: 0.3rem 0;
}

.summary-row + .summary-row {
  border-top: 1px solid var(--border);
}

.summary-label { color: var(--text-dim); }
.summary-value { color: var(--text); font-weight: 500; }
.summary-value.winner { color: var(--green); }
.summary-value.loser { color: var(--red); }

.summary-verdict {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.78rem;
  padding: 0.5rem 0 0.2rem;
  border-top: 1px solid var(--border);
}

.verdict-label { color: var(--text-muted); }
.verdict-value { color: var(--green); font-weight: 500; }

/* --- charts --- */

.chart-container {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.75rem;
  margin-bottom: 1rem;
}

.chart-container h3 {
  font-size: 0.72rem;
  font-weight: 500;
  color: var(--text-dim);
  margin-bottom: 0.5rem;
}

.chart-wrapper {
  position: relative;
  width: 100%;
  overflow: hidden;
}

.chart-wrapper.breakdown { height: 140px; }
.chart-wrapper.sweep { height: 240px; }

.chart-wrapper canvas {
  position: absolute;
  top: 0;
  left: 0;
  width: 100% !important;
  height: 100% !important;
}

/* --- model tab --- */

.model-content {
  font-size: 0.78rem;
  line-height: 1.7;
  color: var(--text-dim);
}

.step {
  display: flex;
  gap: 1rem;
  padding: 1.25rem 0;
  border-top: 1px solid var(--border);
}

.step:first-child { border-top: none; }

.step-num {
  font-size: 0.7rem;
  color: var(--text-muted);
  min-width: 1.5rem;
  flex-shrink: 0;
}

.step h3 {
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--accent);
  margin-bottom: 0.35rem;
}

.step p {
  font-size: 0.78rem;
  color: var(--text-dim);
  line-height: 1.7;
  margin-bottom: 0.5rem;
}

.step p:last-child { margin-bottom: 0; }

.eq-block {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.75rem 1rem;
  margin: 0.5rem 0;
  overflow-x: auto;
  text-align: center;
}

.eq-block .katex { font-size: 0.9rem; }

.step code {
  font-family: var(--mono);
  font-size: 0.72rem;
  color: var(--accent-dim);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 3px;
  padding: 0.1rem 0.3rem;
}

.step em { font-style: italic; color: var(--accent-dim); }

.var-table {
  width: 100%;
  border-collapse: collapse;
  margin: 0.5rem 0;
  font-size: 0.72rem;
}

.var-table th {
  text-align: left;
  color: var(--text-muted);
  font-weight: 400;
  padding: 0.3rem 0.5rem;
  border-bottom: 1px solid var(--border);
}

.var-table td {
  padding: 0.3rem 0.5rem;
  border-bottom: 1px solid var(--border);
  color: var(--text-dim);
}

.var-table td:first-child {
  color: var(--accent-dim);
  white-space: nowrap;
}

/* --- note --- */

.note {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.75rem;
  font-size: 0.72rem;
  color: var(--text-dim);
  line-height: 1.7;
  margin: 0.75rem 0;
}

/* --- footer --- */

footer {
  margin-top: auto;
  padding-top: 3rem;
  font-size: 0.7rem;
  color: var(--text-muted);
}

footer a {
  color: var(--text-dim);
  text-decoration: none;
  transition: color 0.15s;
}

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

/* --- hidden --- */

.hidden { display: none !important; }

/* --- responsive --- */

@media (max-width: 500px) {
  #app { padding: 1.5rem 1rem; }
  .param-grid.cols-3 { grid-template-columns: auto 1fr 1fr; }
  .preset-bar { gap: 0.35rem; }
  .preset { font-size: 0.65rem; padding: 0.3rem 0.5rem; }
  .step { flex-direction: column; gap: 0.5rem; }
}

/* --- scrollbar --- */

::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--border-light); border-radius: 3px; }